Method for removing lead from painted drawings by means of laser photodynamic action

Abstract

A method for removing lead return of colored drawing by using laser photodynamic, the laser with central wavelength of 650nm irradiates porphyrin to generate singlet oxygen to repair various colored drawing cultural relics lead return, thereby reducing the demand for laser power in the repair process, avoiding the ablation effect in the laser irradiation process, and further reducing the damage to the calligraphy and painting cultural relics in the traditional laser cleaning process. Through the control of laser power and the control of porphyrin solution concentration, the directional oxidation of the pollutant lead sulfide is realized, and the oxidation of the cultural relic body substrate is avoided, so that the accurate repair of the lead return part is realized, and the surface burning and damage of the colored drawing cultural relics are avoided. The application is suitable for a wide range of materials, can be applied to paper, silk, murals, stone and other inorganic calligraphy and painting cultural relics, greatly expands the repair material range, and has the advantages of low cost, low cultural relic damage, high reduction degree and high controllability, and is a very excellent repair technology.

Description

Technical Field

[0001] This invention relates to the field of calligraphy and painting preservation, specifically a method for removing lead residue from the surface of painted cultural relics using laser photodynamic therapy. Background Technology

[0002] Lead white, a commonly used white pigment in ancient times, was widely used in various painted cultural relics. However, during long-term preservation, lead white reacts with hydrogen sulfide in the air, sulfur-containing amino acids in the surrounding pigment, and other sulfur-containing components to transform into brown or black lead sulfide. This distorts the original appearance and color of the painted cultural relics, affecting their true representation and reducing their artistic value. This phenomenon is called lead reversion. Lead reversion is particularly prevalent in various types of painted cultural relics, such as those in grotto murals and ancient paintings. The distribution of lead reversion areas is uneven, varying in size and shape, including linear, dotted, and patchy areas. These areas are scattered, large in scale, and require precise treatment. To restore the original appearance of the lead reversion areas, traditional methods often use oxidants to oxidize the brown lead sulfide into white lead sulfate, achieving recoloring. Oxidants used include hydrogen peroxide and organic peroxides. However, this method has the problem of the oxidizing agent seeping into and contaminating the surrounding pigment, leading to fading, and also requires a high level of skill from the operator.

[0003] Patent CN201710665089.7 discloses a method for removing lead residue from ancient paintings by oxidizing lead residue with nano-calcium peroxide. This invention proposes a solution for converting pollutants through oxidation during the restoration of lead residue in ancient paintings, but it requires a higher level of technical skill from the restorers. Patent CN201820112310.6 discloses a composite electrode device for restoring lead residue on the surface of painted artifacts using an electrochemical oxidation method. Compared to traditional lead removal methods, this method offers improved safety and causes less damage to the artifacts compared to methods that directly remove pollutants, resulting in better restoration effects. However, it places high demands on the artifact itself, particularly requiring that the front and back surfaces of the lead residue area form an oxidation-reduction couple. This is difficult to apply to murals or other large, immobile artifacts. Furthermore, the processing area remains difficult to control, and it is still unavoidable that other pigments near the restoration area will be bleached or oxidized by the oxidizing agent used during the restoration process.

[0004] Compared to traditional chemical oxidation methods for treating lead-returned parts, laser photodynamic catalysis has lower environmental requirements and better controllability. Sichuan University disclosed a device for laser photodynamic catalysis to degrade organic pollutants in water in its utility model patent (CN202123168602.2). Tianjin University disclosed a method for preparing mesoporous nitrogen-doped graphene supported on molybdenum disulfide by laser irradiation and its application in electrocatalytic hydrogen production in its patent (CN201910829683.4). Wuhan Optics Valley Aerospace Sanjiang Laser Industry Technology Research Institute Co., Ltd. disclosed an air purification device and method based on ultraviolet laser and TiO2 photocatalysis in its patent (CN202011044540.1). Patent CN202211215324.8 discloses a nanomaterial for photocatalysis and photodynamic therapy, its preparation method, and its application. Leshan Jingyuan Water Treatment Equipment Co., Ltd. disclosed a photocatalytic device for treating hospital wastewater in patent CN201821430840.1. Nanjing Maidwen Environmental Protection Technology Co., Ltd. disclosed an ozone photocatalytic reaction deep treatment device, treatment method, and its application in patent CN201510098519.2.

[0005] The aforementioned inventions demonstrate that laser photodynamic catalysis has strong applicability, reducing the environmental impact of chemical reactions through the high energy density of lasers and promoting redox reactions of inorganic and organic matter. In the laser photodynamic catalysis and catalytic oxidation processes, the inventions utilize laser irradiation to promote oxidation or coordination reactions, enabling the smooth progress of organic matter oxidation and decomposition, inorganic matter oxidation and precipitation transformation, and allowing reactions on various substrate surfaces with low requirements for substrate materials. However, the solid catalytic materials used are not easily compatible with the surface of painted and calligraphic artifacts, limiting the scope of restoration and easily causing damage such as collisions and scratches. Furthermore, the high laser intensity in these inventions may cause ablation or other damage to artifacts due to improper operation, thus limiting their application in artifact conservation and restoration.

[0006] Therefore, there is an urgent need for a restoration method that can combine laser photodynamic catalysis with lead repainting restoration of painted cultural relics, and achieve a precise and safe method for non-destructive restoration of lead repainting of painted cultural relics. Summary of the Invention

[0007] To overcome the problems of bleaching, oxidation damage, and pollution to the painted artifacts during the lead repainting process in traditional chemical restoration techniques, as well as the potential for ablation on the artifact surface by existing laser cleaning techniques, this invention proposes a method for removing lead repainting using laser photodynamic therapy.

[0008] The method for removing lead residue from painted artifacts proposed in this invention includes removing lead residue from the surface of painted calligraphy and paintings and painted murals. The specific process is as follows:

[0009] Step 1: Identify the areas on the surface of the artifact that require restoration.

[0010] The height-adjustable laser support is placed on the horizontal platform.

[0011] The surface of the cultural relic to be restored was divided into multiple blocks; each block was measured sequentially using a colorimeter, and the color difference between each block and the lead white standard sample was obtained as a comprehensive evaluation index △E.

[0012] For painted and colored cultural relics, the area with a color difference assessment index △E>5 compared to the lead white standard sample is designated as the area on the surface of the painted and colored cultural relic to be repaired.

[0013] For murals and painted artifacts, the areas with a color difference assessment index △E>5 compared to the lead white standard sample are designated as the areas on the surface of the murals and painted artifacts to be repaired.

[0014] Step 2, determine the laser power density for the area to be repaired:

[0015] The relationship between laser power density and laser irradiation distance for the restoration of painted cultural relics is ρ=P / S=P / f(h); the units are W / mm². 2 .

[0016] The laser irradiation conditions include the repair laser power density ρ, the laser spot area S, the laser irradiation distance h, and the laser power P. S = f(h); the laser irradiation distance h is the distance between the laser output port and the simulated sample.

[0017] The repair laser power density ρ includes the repair laser power density ρ on the surface of calligraphy and painting artifacts. z Laser power density ρ for the restoration of murals and painted artifacts b The laser spot area S includes the laser spot area S for the restoration of calligraphy, paintings, and cultural relics. z The area of ​​light spots during the restoration of murals and painted cultural relics (S) b The laser irradiation distance h includes the laser irradiation distance h for the restoration of calligraphy, paintings, and other cultural relics. z Laser irradiation distance h for mural and painted cultural relic restoration b Laser power P includes P for the restoration of calligraphy, paintings, and other cultural relics. z P and mural painting cultural relics restoration b .

[0018] Laser power density ρ for the restoration of painted and calligraphic artifacts z 1.20~2.00W / mm 2Laser power density ρ for the restoration of murals and painted artifacts b The value is 1.50~2.24W / mm. 2 .

[0019] When determining the laser power density ρ for the area to be repaired, the laser power P is measured using a power meter. Then, f(h) is measured, where f(h) is a function of the spot area S and the distance h.

[0020] The process of measuring f(h) involves assuming the lateral length of the laser spot is x and the longitudinal width is y, thus the area of ​​the laser is S = x·y. When the distance h between the laser's output port and the simulated sample takes different values, the corresponding lateral length x and longitudinal width y of the laser spot are measured.

[0021] Step 3, Safety verification of power density in the laser irradiation area:

[0022] The safety of the selected restoration laser power density was verified. Simulated samples of painted calligraphy and mural artifacts were prepared and tested for verification.

[0023] The simulated cultural relics samples of calligraphy and painting are made of the same type of raw Xuan paper as the cultural relics, and the surface is coated with black lead sulfide until the surface turns completely black.

[0024] The substrate of the simulated mural artifact is the same as that of the mural artifact, and the surface of the substrate is coated with black lead sulfide until the surface is completely black.

[0025] A simulated sample of a calligraphy and painting artifact is irradiated with a laser to observe whether there is any burning or ablation damage on the surface of the simulated sample; if the simulated sample of the calligraphy and painting artifact is undamaged, the initial restoration power density ρ is verified based on the current safety standards. zn The power density ρ of the surface of calligraphy and painting cultural relics awaiting restoration z The laser irradiation distance h between the current laser output port and the simulated sample is... zn The laser irradiation distance h between the laser output port and the simulated sample during the repair process. z If the simulated cultural relic of calligraphy and painting is damaged, the laser irradiation distance h is adjusted. zn This allows for the acquisition of a new restoration power density until the simulated sample of the painted calligraphy and painting artifact is undamaged, and the current laser irradiation distance h is used to determine the restoration power density. zn The laser irradiation distance h between the laser output port and the simulated sample during the repair process. z To repair power density ρ zn The power density ρ of the surface of calligraphy and painting cultural relics awaiting restoration z ;

[0026] The simulated mural and painted artifact sample was irradiated with a laser to observe whether there was any burning or ablation damage on the surface of the simulated sample; if the simulated artifact sample showed no damage, the initial restoration power density ρ was verified based on the current safety standards. bn The power density ρ of the surface of calligraphy and painting cultural relics awaiting restoration b The laser irradiation distance h between the current laser output port and the simulated sample is... bn The laser irradiation distance h between the laser output port and the simulated sample during the repair process. b If the simulated cultural relic of calligraphy and painting is damaged, the laser irradiation distance h is adjusted. bn This allows for the acquisition of a new restoration power density until the simulated sample of the painted calligraphy and painting artifact is undamaged, and the current laser irradiation distance h is used to determine the restoration power density. bn The laser irradiation distance h between the laser output port and the simulated sample during the repair process. b To repair power density ρ bn The power density ρ of the surface of calligraphy and painting cultural relics awaiting restoration b ;

[0027] The specific process of the test verification is as follows:

[0028] Ⅰ When testing and verifying the laser power density ρ for the restoration of calligraphy, paintings, and colored cultural relics z When it comes to security:

[0029] The initial value ρ of the repair laser power density z0 =1.2~2.0W / mm 2 The values ​​in the table are used as the initial repair power density for safety verification; the distance between the laser output port and the simulated sample is used as the initial laser irradiation distance h for safety verification. z0 The initial value ρ of the repair laser power density is then sequentially adjusted. z0 The simulated sample was irradiated with laser for 10 minutes, and the irradiated area was checked for yellowing or discoloration caused by burning or ablation.

[0030] If the initial value of the repair laser power density ρ is given in each of the aforementioned repair laser power densities z0 If the simulated samples of calligraphy, paintings, and colored cultural relics do not turn yellow, it indicates that the restoration process is safe and without damage. Therefore, the initial restoration power density ρ is verified based on the current safety profile. z0 The power density ρ of the surface of calligraphy and painting cultural relics awaiting restoration z The laser irradiation distance h between the current laser output port and the simulated sample is... z0 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. z .

[0031] If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance h is increased.z Each time the laser irradiation distance is increased by 1mm, a new laser irradiation distance h is obtained. z1 The new relationship between power density and laser irradiation distance ρ z1 =P z / S z =P z / f(h z1 ).

[0032] Using the new power density ρ again z1 Irradiate the simulated sample with laser for 5 minutes. Observe whether the surface of the simulated sample shows yellowing or discoloration due to burning or ablation. If the simulated sample does not show yellowing, then apply the current repair power density ρ. z1 As the repair power density ρ z The laser irradiation distance h between the current laser output port and the simulated sample is... z1 The laser irradiation distance h during repair z If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance is further increased; the increased laser irradiation distance is 1 mm, resulting in a new laser irradiation distance h. z2 The new formula for the relationship between power density and laser irradiation distance ρ z2 =P z / S z =P z / f(h z2 ).

[0033] Repeat the process of irradiating the simulated sample with a new repair power density, observing whether burning or ablation occurs on the surface of the simulated sample, and continuing to increase the laser irradiation distance until the surface of the simulated sample no longer shows yellowing or discoloration due to burning or ablation, and determine the current repair power density ρ. zn The power density ρ for the restoration of this cultural relic and calligraphy z Determine the laser irradiation distance h between the laser output port of the current laser and the simulated sample. zn h is the laser irradiation distance between the laser output port and the simulated sample. z .

[0034] II. When testing and verifying the laser power density for the restoration of the surface area of ​​the mural-painted cultural relic,

[0035] The initial value ρ of the repair laser power density b0 =1.50~2.24W / mm 2 The values ​​in the table are used as the initial repair power density for safety verification; the distance between the laser output port and the simulated sample is used as the initial laser irradiation distance h for safety verification. b0 The initial value ρ of the repair laser power density is then sequentially adjusted.b0 The simulated sample was irradiated with laser for 10 minutes, and the irradiated area was checked for yellowing or discoloration, which are caused by burning or ablation.

[0036] If the simulated sample does not turn yellow, it indicates that the repair process is safe and without damage. Therefore, the initial repair power density ρ is verified based on the current safety profile. b0 As the repair power density ρ b The laser irradiation distance h between the current laser output port and the simulated sample is... b0 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. b .

[0037] If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance h should be increased. b Each time the laser irradiation distance is increased by 1mm, a new laser irradiation distance h is obtained. b1 The new relationship between power density and laser irradiation distance ρ b1 =P b / S b =P b / f(h b1 ).

[0038] Using the new power density ρ again b1 Irradiate the simulated sample with a laser for 10 minutes. Observe whether the surface of the simulated sample shows yellowing or discoloration due to burning or ablation. If the simulated sample does not show yellowing, then apply the current repair power density ρ. b1 As the repair power density ρ b The laser irradiation distance h between the current laser output port and the simulated sample is... b1 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. b If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance is increased by 1 mm to obtain the new laser irradiation distance h. b2 The new relationship between power density and laser irradiation distance ρ b2 =P b / S b =P b / f(h b2 ).

[0039] Repeat the process of irradiating the simulated sample with a new repair power density, observing whether burning or ablation occurs on the surface of the simulated sample, and then continuing to increase the laser irradiation distance h. b The process continues until the simulated sample surface shows no yellowing or discoloration due to burning or ablation. At the current repair power density ρ bnThe power density ρ of the restoration of this mural-painted cultural relic b The laser irradiation distance h between the current laser output port and the simulated sample is... bn The laser irradiation distance h, which is the painted artifact of this mural, is... b .

[0040] Step 4, Lead restoration of painted cultural relics:

[0041] The lead restoration includes painted calligraphy and mural artifacts.

[0042] During lead repatriation repair, the determined repair power density and laser irradiation distance of the laser are used as the power density for lead repatriation repair and the laser irradiation distance between the laser output port and the simulated sample.

[0043] Based on the comprehensive evaluation index △E of the color difference between each area to be repaired on the surface of the painted cultural relic and the lead white standard sample, the concentration of porphyrin solution and the laser irradiation time used for each area to be repaired were determined.

[0044] The areas to be repaired were repeatedly repaired in sequence to complete the lead restoration of the painted cultural relic surface.

[0045] When performing lead restoration on painted and colored cultural relics, the porphyrin solution concentration is 5 mg / L and the laser irradiation time is 3 minutes when the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample is 5. Based on this, for every increase of 1 in the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample, the porphyrin solution concentration increases by 0.125 mg / L and the irradiation time increases by 3 seconds.

[0046] When performing lead-based restoration on painted murals, the porphyrin solution concentration was 10 mg / L and the laser irradiation time was 5 minutes when the overall color difference assessment index ΔE between the area to be restored and the lead white standard sample was 5. Based on this, for every 1 decrease in the overall color difference assessment index ΔE between the area to be restored and the lead white standard sample, the porphyrin solution concentration increased by 0.125 mg / L and the irradiation time increased by 5 seconds.

[0047] The specific process of sequentially repairing each area on the surface of the painted cultural relic is as follows:

[0048] I. Repair of the first area to be repaired.

[0049] The first area to be repaired was treated using a method of repeated irradiation and multiple repairs. Specifically:

[0050] i. First repair of the first area to be repaired. Measure and record the comprehensive evaluation index ΔE of the color difference between the first area to be repaired and the lead white standard sample, and determine the concentration of the porphyrin solution and the laser irradiation time.

[0051] The porphyrin solution is sprayed onto the surface of the first area to be repaired according to the determined concentration, thus wetting the area. The surface of the first area to be repaired, coated with the porphyrin solution, is then irradiated with a laser. After irradiation, the laser is turned off, completing the first stage of lead repainting repair on the first area to be repaired.

[0052] ii. Second repair of the first area to be repaired. Restore the position of the laser. Position the laser output port directly towards the first area to be repaired after the first repair; remeasure the color difference comprehensive evaluation index ΔE between the first area to be repaired and the lead white standard sample to obtain a new color difference value; based on the obtained new color difference value, determine the required concentration of porphyrin solution and the laser irradiation time to obtain the required porphyrin solution concentration and laser irradiation time for the second repair of the first area to be repaired.

[0053] Weigh out the porphyrin solution and spray it onto the surface of the first area to be repaired, which has already undergone the first repair. Then, irradiate the surface of this first area with the porphyrin solution sprayed on it using a laser. This completes the second repair of the lead-returning repair on the first area to be repaired.

[0054] iii. Repair the remaining areas of the first area to be repaired. Repeat the second repair process for the first area to be repaired, sequentially completing the remaining repairs based on the current color difference of the first area, the determined concentration of the required porphyrin solution, and the determined laser irradiation time, until the difference between the measured comprehensive color difference evaluation index ΔE with the lead white standard sample and the measured comprehensive color difference evaluation index ΔE obtained in the previous repair is less than 1. The repair of the first area to be repaired is then complete.

[0055] II. Repair of the second area to be repaired

[0056] i. Adjust the platform position to move the laser spot to the next area to be repaired. Repeat the process of repairing the first area to be repaired, and complete each repair step for the second area to be repaired based on the comprehensive evaluation index ΔE of the color difference between the current area to be repaired and the lead white standard sample, the determined concentration of the current porphyrin solution, and the determined current laser irradiation time.

[0057] ii. Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired to complete the repair of the second area to be repaired.

[0058] III. Repair of the remaining areas to be repaired

[0059] Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired, until all areas to be repaired are repaired, thus completing the lead restoration work on the surface of the painted cultural relic.

[0060] Step 4, winding up:

[0061] After the restoration is completed, the restored calligraphy and painting artifacts are left to dry at room temperature before being rolled up and stored.

[0062] This invention proposes a laser photodynamic catalytic restoration method that can be widely used for the removal of lead from painted cultural relics, such as murals in grottoes and paintings in ancient calligraphy and paintings.

[0063] This invention utilizes laser irradiation to generate singlet oxygen, specifically oxidizing lead sulfide, the contaminant causing lead reversion in painted cultural relics, thus restoring the problem of lead reversion. Laser irradiation excites a photosensitive reagent, which then undergoes energy state transformation to generate singlet oxygen. This generated singlet oxygen oxidizes the lead sulfide contaminant, reducing the laser power required for restoration and avoiding ablation effects during laser irradiation. This minimizes damage to the painted cultural relics caused by traditional laser cleaning methods. Porphyrin was selected as the photosensitive reagent after screening numerous options. It generates a suitable concentration of singlet oxygen, and at a catalytic concentration, the solution is colorless and transparent with a certain degree of volatility, allowing it to automatically detach from the surface of the painted cultural relics with minimal impact. Different wavelengths of laser were used to catalyze porphyrin, and it was found that the laser with a central wavelength of 650 nm had a better catalytic effect. By controlling the laser power and the concentration of the porphyrin solution, the concentration of singlet oxygen was controlled, thereby achieving targeted oxidation of the contaminant lead sulfide and avoiding oxidation of the artifact's substrate, thus enabling precise restoration of the lead-returned areas. Safety and effectiveness tests were conducted on various painted artifact substrates using this method. The results showed that when the power density of the repair laser generated by the continuous laser is 1.50 W / cm², the restoration is successful. 2 Up to 2.24 W / cm 2 Within the specified range, it will not cause surface burning or damage to painted cultural relics, and can also generate singlet oxygen for oxidation.

[0064] A 10 mg / L porphyrin solution was sprayed onto raw Xuan paper, commonly used in calligraphy and painting artifacts, and onto the ground layer, commonly used in mural calligraphy and painting artifacts. A semiconductor laser with a center wavelength of 650 nm and a power density of 2.24 W / cm² was used. 2Safety tests were conducted by irradiating raw Xuan paper and ground layer coated with porphyrin solution for 10 minutes. The results showed no ablation caused by laser irradiation on either surface, demonstrating the safety of the treatment method. 5g of basic lead carbonate and 2ml of gelatin solution were ground and stirred to prepare lead white pigment, a material used in calligraphy and painting. This pigment was applied to raw Xuan paper and ground layer, and a 2g / L sodium sulfide solution was sprayed onto the left side of the pigment-coated area to generate lead sulfide contaminants, thus preparing a simulated lead-return sample of the calligraphy and painting artifact. The boundary areas treated with and untreated with sodium sulfide were then irradiated and repaired under the same conditions as in the safety tests to conduct effectiveness tests. Effectiveness tests showed that areas contaminated with lead sulfide, after being sprayed with porphyrin solution and irradiated by laser, turned significantly whiter, demonstrating a clear remediation effect. Other areas, such as those contaminated with lead sulfide only after irradiation, those contaminated with lead sulfide only after spraying with porphyrin, and those irradiated with both porphyrin and lead sulfide but without lead sulfide contamination, showed no changes. Similarly, no laser-induced ablation was observed. These results indicate that this method specifically oxidizes lead sulfide and is highly effective. Its oxidation effect is highly targeted and does not affect uncontaminated areas.

[0065] The surface of the painted and colored cultural relics is divided into 1cm×1cm square blocks. A colorimeter is used to measure the ΔE corresponding to each block of the painted and colored cultural relics relative to lead white. All colors can be perceived and measured through the Lab color space. These data can also be used to represent the color difference between the standard sample and the test sample, and ΔE is usually used as the comprehensive evaluation index of color difference.

[0066] When ΔE is between 0 and 1, the color difference is imperceptible to the naked eye; when ΔE is between 1 and 2, it is slightly noticeable; when ΔE is between 2 and 3, the color difference between materials can be distinguished more clearly; when ΔE is between 3.5 and 5, the color difference is very obvious; and when ΔE is above 5, the color difference is very large, and it may even appear as two different colors. Areas with a value of 3.5 or higher are designated as the areas to be restored on the surface of the painted artifact. The restoration method proposed in this invention possesses advantages such as low cost, minimal damage to the artifact, high fidelity, and high controllability, making it an excellent restoration technique.

[0067] This invention offers significantly superior controllability compared to traditional chemical methods, while also incurring far lower labor costs. Traditional chemical methods often employ oxidizing agents such as hydrogen peroxide, leading to chemical infiltration during the restoration process. This can easily affect the surrounding areas of the area being repaired. Furthermore, under the influence of oxidizing agents like hydrogen peroxide, the pigment color in the surrounding areas can easily change, such as fading or altering its appearance. Simultaneously, the substrate material of the artifact can be affected; for example, paper artifacts are prone to internal fiber breakage and reduced folding resistance, metal materials are susceptible to oxidation and corrosion, and stone artifacts are prone to changes in porosity and pH levels. In contrast, the restoration method proposed in this invention exhibits virtually no oxidizing properties in the absence of laser irradiation, and the solution is colorless and transparent at low concentrations. Therefore, the restoration process avoids damage to the artifact's substrate and painted layers due to physical processes such as infiltration. Additionally, the laser offers excellent controllability, allowing for precise selection of the irradiation area without affecting other areas. Meanwhile, laser operation is convenient, and compared to the high skill requirements of traditional chemical restoration processes, the restoration method proposed in this paper is simpler to operate and significantly reduces labor costs. Combined, this restoration method has significant advantages over traditional chemical restoration methods in terms of controllability and cost.

[0068] This invention significantly outperforms traditional laser ablation methods for cleaning and repairing artifacts in terms of minimal damage, high restoration accuracy, and cost. Traditional laser ablation methods achieve repair or cleaning by rapidly ablating contaminated areas with high instantaneous energy. This is achieved by increasing the energy in each pulse and compressing its duration. When the pulse duration is in the nanosecond and picosecond range commonly used in artifact restoration, the temperature of the repaired area rises rapidly, sometimes reaching thousands of degrees Celsius, due to the need for sufficient energy to melt and evaporate the material. This poses a significant safety risk to organic artifacts such as paper, potentially causing irreparable damage. Furthermore, the high instantaneous surface temperature causes the lead white pigment on the artifact's surface to react chemically with oxygen and other substances in the air, generating secondary pollutants such as lead and lead oxide, further contaminating the artifact. Therefore, direct laser ablation has significant drawbacks in addressing lead reversion issues in artifact restoration. While the aforementioned safety and secondary contamination risks are reduced when pulse durations are in the femtosecond or attosecond range, the equipment cost increases significantly. Currently, femtosecond lasers can cost millions of yuan, while attosecond lasers are even more expensive, leading to excessively high costs for the entire restoration process and posing certain safety hazards. Furthermore, these lasers are larger and less convenient to use, presenting numerous limitations. For some immovable cultural relics, such as murals, on-site restoration is difficult. Therefore, laser ablation is clearly insufficient for the lead white pigment restoration of cultural relics. The laser photodynamic restoration method proposed in this paper does not use laser ablation to achieve the restoration effect, thus eliminating the need for extremely high single-pulse energy and avoiding the risk of damage to organic cultural relics. It also avoids the risk of secondary contamination caused by the decomposition of lead white pigment due to high temperatures, thereby achieving better restoration results with lower damage. Meanwhile, since ablation is not performed using extremely high laser pulse energy, non-pulsed lasers can be selected, i.e., continuous light lasers. Continuous light lasers are relatively inexpensive, costing less than a thousand yuan. Therefore, direct laser ablation has significant advantages in minimizing damage to cultural relics, improving restoration accuracy, and reducing costs.

[0069] Traditionally, the use of porphyrins in photodynamic chemistry requires a concentration of 5% (20 g / L) or higher. However, at higher concentrations, the porphyrin solution appears yellow, which can cause yellowing of the repaired area if used directly for artifact restoration, making it unsuitable for artifact restoration. Furthermore, research on the photochemistry of porphyrins has traditionally focused on modifying the corresponding groups to enhance the oxidation properties of porphyrin compounds under light irradiation. This invention innovatively utilizes the relatively weak oxidizing properties of porphyrins under light irradiation to achieve directional oxidation of lead sulfide under laser irradiation while avoiding secondary damage to artifacts, especially organic artifacts, caused by the oxidizing properties of the reagents in the unirradiated state. Simultaneously, the innovative use of high laser light intensity increases the rate at which singlet oxygen is generated in the porphyrin solution, promoting the production of singlet oxygen to the concentration required for lead sulfide oxidation. This reduces the required porphyrin concentration in the solution to 10 micrograms per milliliter (10 milligrams per liter), or less than 0.01%. At this concentration, the solution is colorless and transparent, avoiding the yellowing problem caused by relatively high porphyrin concentrations after remediation. Combining these two approaches, ultra-low concentration porphyrin solutions were used for laser photodynamic therapy to restore lead-returned artifacts, enabling the application of photodynamic therapy in the field of artifact restoration. This avoids the risks of secondary contamination and manpower requirements associated with traditional chemical restoration methods, while fully utilizing oxidizing reagents to oxidize lead sulfide and achieve high restoration of lead white color. In the experiment, the color difference between the sample after three restorations and the uncontaminated sample was only 0.16, indicating that the method effectively restored the original artifact's color. After testing, the Lab value calculated using the Lab color model specified by the International Commission on Illumination showed that the ΔE between the restored sample and the uncontaminated lead white sample decreased from 26.78 after contamination to 3.73, indicating that the sample's color was well restored. This method also avoids the risks of damage to artifacts and high equipment costs associated with high-energy pulsed lasers, while fully utilizing the high controllability of lasers. Thus, it finally achieves a low-cost, low-damage, high-restoration, and highly controllable solution to the problem of lead-returned artifact restoration. Furthermore, because this treatment method causes minimal damage, it is applicable to a wide range of materials, including inorganic calligraphy and painting artifacts such as paper, silk, murals, and stone, greatly expanding the range of materials that can be restored. Attached Figure Description

[0070] Figure 1 X-ray electron diffraction patterns of the products before and after repair.

[0071] Figure 2 These are the Raman scattering spectra before and after the restoration.

[0072] Figure 3 These are optical microscope images of the repaired and unrepaired areas.

[0073] Figure 4 These are before-and-after comparison images of the paper sample after restoration; among them, Figure 4 a is an uncontaminated sample; Figure 4 b is the contaminated sample; Figure 4 c is the sample after one repair; Figure 4 d is the sample after the second repair.

[0074] Figure 5 These are scanning electron microscope images of the samples before and after the repair; among them, Figure 5 a is the surface before repair; Figure 5 b is the section before repair; Figure 5 c. The surface before repair is; Figure 5 d is the cross section after repair.

[0075] Figure 6 This is a flowchart of the present invention.

[0076] In the figure: 10. X-ray electron diffraction pattern of lead white pigment; 11. X-ray electron diffraction pattern of the repaired product; 12. Raman absorption peak of lead white pigment; 13. Raman absorption peak of the repaired product; Detailed Implementation

[0077] Example 1

[0078] This embodiment describes a method for restoring lead content in calligraphy and painting artifacts made of Xuan paper using a linear laser. The linear laser is a semiconductor continuous laser with a maximum power P of 2.24W, a center wavelength of 650nm, a set heat dissipation temperature of 23℃, and is powered by 220V, 50Hz AC power. Appropriate laser goggles are worn, and the room temperature during the restoration process is 20℃.

[0079] The specific process of the repair is as follows:

[0080] Step 1: Identify the areas on the surface of the painted or calligraphic artifacts that require restoration:

[0081] The height-adjustable laser support is placed on a horizontal platform. The height-adjustable laser support utilizes existing technology.

[0082] A 1mm thick layer of absorbent paper is evenly laid on the horizontal platform where the adjustable laser bracket is placed, positioned below the laser clamp 3 of the linear laser adjustment device. The calligraphy or painting to be cleaned is then laid flat on the absorbent layer, ensuring good contact between the calligraphy / painting and the surface of the absorbent layer.

[0083] The surface of the painted and colored cultural relics is divided into 1cm×1cm square blocks. A colorimeter is used to measure the ΔE corresponding to each block of the painted and colored cultural relics relative to lead white. All colors can be perceived and measured through the Lab color space. These data can also be used to represent the color difference between the standard sample and the test sample, and ΔE is usually used as the comprehensive evaluation index of color difference.

[0084] When ΔE is 0-1, color difference cannot be distinguished visually; when ΔE is 1-2, slight color difference can be discerned visually; when ΔE is 2-3, color difference between materials can be clearly distinguished; when ΔE is 3.5-5, color difference is very obvious; when ΔE is above 5, color difference is very large, even perceived as two different colors. Areas with a value of 3.5 or higher are designated as the areas to be restored on the surface of the painted artifact.

[0085] Step 2: Determine the laser power density for the area to be repaired.

[0086] The laser irradiation conditions include the repair power density ρ of the laser irradiation area, the laser spot area S, the laser irradiation distance h, and the laser power P. The laser irradiation distance h is the distance between the laser output port and the simulated sample.

[0087] Controlling the power density ρ of the laser irradiation area is crucial during the restoration process. The power density ρ is related to both the laser power P and the laser spot area S, where ρ = P / S, and the unit is W / mm². 2 The linear laser emitted by the laser diverges linearly along a certain direction, meaning the laser spot area S is linearly related to the laser irradiation distance h between the sample and the laser outlet. In other words, the spot area S is a linear function of the irradiation distance h, and therefore can be represented by a linear function f(h) of the irradiation distance h, i.e., S = f(h). Since the power density ρ = P / S, it is also distance-dependent, and its expression can be further transformed into ρ = P / S = P / f(h). Therefore, to control a suitable power density ρ, it is necessary to first obtain the function f(h) of the spot area S and the irradiation distance h. This yields the relationship between power density ρ and irradiation distance h: ρ = P / S = P / f(h). The power density ρ can then be precisely controlled using the irradiation distance h, and the irradiation distance h can be selected based on the chosen power density.

[0088] In performing f(h) z During measurement, let the lateral length of the laser spot be x and the longitudinal width be y, therefore the area of ​​the laser S = x·y. When the distance h between the laser outlet and the simulated sample takes different values, the corresponding lateral length x and longitudinal width y of the laser spot are measured respectively.

[0089] This embodiment describes a method for restoring lead content in painted calligraphy and paintings using laser photodynamic therapy. The linear laser is mounted on a laser fixture within an adjustable laser support and connected to a 220V, 50Hz AC power supply.

[0090] The restoration power density ρ is the laser power density for calligraphy and painting restoration. z , ρ z =P z / S z The unit is W / mm 2 In the formula, P z Laser power for calligraphy and painting restoration, S z The area of ​​the laser spot used for restoring calligraphy and paintings.

[0091] S z =f(h z ); h in the formula z This refers to the laser irradiation distance between the laser output port and the simulated sample during the restoration of calligraphy, painting, and colored cultural relics.

[0092] Therefore ρ z =P z / S z =P z / f(h z )

[0093] Determining the laser power density ρ for the restoration of calligraphy, paintings, and colored cultural relics z initial value ρ z0 The value is 1.50~2.24W / mm. 2 .

[0094] In determining the repair laser power density ρ z At that time, the laser power P was measured by a power meter. z Perform f(h) measurement, wherein f(h) z ) is the area S of the light spot. z With distance h z The function;

[0095] Turn on the linear laser and directly measure the laser power P using a power meter. z 1.12W. Perform f(h) z The measurement method is as follows: Let the horizontal length of the laser spot be x, and the vertical width be y, then the area S of the laser is... z =x*y. When the laser irradiation distance is h z When different values ​​are taken, the lateral length x and longitudinal width y of the corresponding laser spot are measured respectively. The results show that when the laser irradiation distance h is taken, the laser spot is irradiated at a distance of 1000 meters. zWhen the diameters are 20mm, 30mm, 40mm, 50mm, and 60mm, the corresponding transverse lengths x are 18mm, 26mm, 34mm, 42mm, and 50mm, respectively; and the corresponding longitudinal widths y are 1mm, 1mm, 1mm, 1mm, and 1mm, respectively. This indicates that the laser emitted by the laser diverges linearly along the transverse direction of the laser spot, while remaining constant in the longitudinal direction of the laser spot.

[0096] The laser irradiation distance h z A linear fit is performed on the corresponding horizontal length x to obtain the fitting relationship between the horizontal width x and the laser irradiation distance h, x=g(h). The vertical width y does not change with the laser irradiation distance h and remains constant at 1mm. The spot area S=x×y=g(h)×1mm is then obtained, thus yielding the linear function S of the spot area S with respect to the laser irradiation distance h: S=f(h)=g(h)×1mm, which gives the relationship ρ between the repair power density and the distance. z =P z / S z =P z / f(h z ).

[0097] The relationship between the repair laser power density and distance is expressed by the formula ρ. z =P z / S z =P z / f(h z Adjust the laser irradiation distance h by rotating the bracket knob. z To achieve the change in repair laser power density ρ z This allows for the simulation of different repair laser power densities ρ. z The repair effect was observed. Results showed that when the repair laser power density was 1.2~2.0 W / mm², the repair was most effective. 2 At this time, catalytic porphyrin produces singlet oxygen without damaging the paper.

[0098] Step 3, Safety verification of laser power density for repairing the laser irradiated area:

[0099] To verify the safety of the power density used for repairing the selected laser irradiation area, a simulated sample was prepared for testing and verification.

[0100] The simulated samples of the calligraphy and painting artifacts were made of the same type of raw Xuan paper as the original artifacts, with black lead sulfide applied to the surface until it turned completely black.

[0101] Verification of laser power density ρ for the restoration of calligraphy, paintings, and colored cultural relics z The specific process of security is as follows:

[0102] The initial value ρ of the repair laser power densityz0 =1.2~2.0W / mm 2 The values ​​in the table are used as the initial repair power density for safety verification; the distance between the laser output port and the simulated sample is used as the initial laser irradiation distance h for safety verification. z0 The initial value ρ of the repair laser power density is then sequentially adjusted. z0 The simulated sample was irradiated with laser for 10 minutes, and the irradiated area was checked for yellowing or discoloration caused by burning or ablation.

[0103] If the simulated sample does not turn yellow, it indicates that the repair process is safe and without damage. Therefore, the initial repair power density ρ is verified based on the current safety profile. z0 As the repair power density ρ z The laser irradiation distance h between the current laser output port and the simulated sample is... z0 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. z .

[0104] If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance h should be increased. z Each time the laser irradiation distance is increased by 1mm, a new laser irradiation distance h is obtained. z1 The new relationship between power density and laser irradiation distance ρ z1 =P z / S z =P z / f(h z1 ).

[0105] Using the new power density ρ again z1 Irradiate the simulated sample with laser for 5 minutes. Observe whether the surface of the simulated sample shows yellowing or discoloration due to burning or ablation. If the simulated sample does not show yellowing, then apply the current repair power density ρ. z1 As the repair power density ρ z The laser irradiation distance h between the current laser output port and the simulated sample is... z1 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. z If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance is increased by 1 mm to obtain the new laser irradiation distance h. z2 The new relationship between power density and laser irradiation distance ρ z2 =P z / S z =P z / f(h z2 ).

[0106] Repeat the process of irradiating the simulated sample with a new repair power density, observing whether burning or ablation occurs on the surface of the simulated sample, and then continuing to increase the laser irradiation distance h. z The process continues until the simulated sample surface shows no yellowing or discoloration due to burning or ablation. At the current repair power density ρ zn The power density ρ of the restoration of this mural-painted cultural relic z The laser irradiation distance h between the current laser output port and the simulated sample is... zn The laser irradiation distance h, which is the painted artifact of this mural, is... z .

[0107] Step 4, Lead restoration of painted cultural relics:

[0108] When restoring painted and colored cultural relics to lead, the determined restoration power density and laser irradiation distance of the laser are used as the power density for lead restoration and the laser irradiation distance between the laser output port and the simulated sample.

[0109] Based on the comprehensive evaluation index △E of the color difference between each area to be repaired on the surface of the painted cultural relic and the lead white standard sample, the concentration of porphyrin solution and the laser irradiation time used for each area to be repaired were determined.

[0110] The areas to be repaired were repeatedly repaired in sequence to complete the lead restoration of the painted cultural relic surface.

[0111] When performing lead restoration on painted and colored cultural relics, if the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample is 5, the concentration of porphyrin solution is 5 mg / L and the laser irradiation time is 3 min. Based on this, for every increase of 1 in the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample, the concentration of porphyrin solution increases by 0.125 mg / L and the irradiation time increases by 3 s.

[0112] The specific process of sequentially repairing each area on the surface of the painted cultural relic is as follows:

[0113] I. Repair of the first area to be repaired.

[0114] The first area to be repaired was treated using a method of repeated irradiation and multiple repairs. Specifically:

[0115] i. First repair of the first area to be repaired. Measure and record the color difference ΔE between the first area to be repaired and the lead white standard sample, and determine the concentration of the porphyrin solution and the laser irradiation time.

[0116] The porphyrin solution is sprayed onto the surface of the first area to be repaired according to the determined concentration, thus wetting the area. The surface of the first area to be repaired, coated with the porphyrin solution, is then irradiated with a laser. After irradiation, the laser is turned off, completing the first stage of lead repainting repair on the first area to be repaired.

[0117] ii. Second repair of the first area to be repaired. Restore the position of the laser. Position the laser output port directly towards the first area to be repaired after the first repair; remeasure the color difference comprehensive evaluation index ΔE between the first area to be repaired and the lead white standard sample to obtain a new color difference value; based on the new color difference value, determine the required concentration of porphyrin solution and the laser irradiation time to obtain the required porphyrin solution concentration and laser irradiation time for the second repair of the first area to be repaired.

[0118] Weigh out the porphyrin solution and spray it onto the surface of the first area to be repaired, which has already undergone the first repair. Then, irradiate the surface of this first area with the porphyrin solution sprayed on it using a laser. This completes the second repair of the lead-returning repair on the first area to be repaired.

[0119] iii. Repair the remaining areas of the first repair area. Repeat the second repair process for the first repair area, sequentially completing the remaining repairs of the first repair area based on the current color difference assessment index ΔE between the first repair area and the lead white standard sample, the determined concentration of the required porphyrin solution, and the determined laser irradiation time, until the difference between the measured color difference assessment index ΔE with the lead white standard sample and the measured color difference assessment index ΔE obtained in the previous repair is less than 1. The repair of the first repair area is then complete.

[0120] II. Repair of the second area to be repaired

[0121] i. Adjust the platform position to move the laser spot to the next area to be repaired. Repeat the process of repairing the first area to be repaired. Based on the comprehensive evaluation index ΔE of the color difference between the current area to be repaired and the lead white standard sample, the determined concentration of the current porphyrin solution, and the determined current laser irradiation time, complete each repair step for the second area to be repaired.

[0122] ii. Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired to complete the repair of the second area to be repaired.

[0123] III. Repair of the remaining areas to be repaired

[0124] Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired, until all areas to be repaired are repaired, thus completing the lead restoration work on the surface of the painted cultural relic.

[0125] Step 5, rewind:

[0126] After the restoration is completed, the restored calligraphy and painting artifacts are left to dry at room temperature before being rolled up and stored.

[0127] Example 2

[0128] This embodiment describes a method for restoring lead content in murals and painted cultural relics using a linear laser. The linear laser is a semiconductor continuous laser with a power P of 2.2W, a center wavelength of 650nm, a set heat dissipation temperature of 23℃, and is powered by 220V, 50Hz AC power. Appropriate laser goggles are worn, and the room temperature during the restoration process is 20℃.

[0129] The specific process of the repair is as follows:

[0130] Step 1: Identify the areas on the surface of the mural-painted artifacts that require restoration:

[0131] The height-adjustable laser support is placed on a horizontal platform. The height-adjustable laser support utilizes existing technology.

[0132] The surface of the painted and colored cultural relics was divided into 1cm×1cm square blocks. A colorimeter was used to measure the ΔE corresponding to each block of the painted and colored cultural relics relative to lead white. All colors were perceived and measured through the Lab color space. These data can also represent the color difference between the standard sample and the test sample, and ΔE is usually used as the comprehensive evaluation index of color difference.

[0133] When ΔE is 0-1, color difference cannot be distinguished visually; when ΔE is 1-2, slight color difference can be discerned visually; when ΔE is 2-3, color difference between materials can be clearly distinguished; when ΔE is 3.5-5, color difference is very obvious; when ΔE is above 5, color difference is very large, even perceived as two different colors. Areas with a value of 3.5 or higher are designated as the areas to be restored on the surface of the painted artifact.

[0134] Step 2: Determine the laser power density for the area to be repaired.

[0135] The laser irradiation conditions include the repair power density ρ of the laser irradiation area, the laser spot area S, the laser irradiation distance h, and the laser power P. The laser irradiation distance h is the distance between the laser output port and the simulated sample.

[0136] The repair power density ρ = P / S, with units of W / mm². 2 In the formula, P is the laser power and S is the laser spot area.

[0137] The laser spot area S = f(h); where h is the laser irradiation distance.

[0138] Therefore, ρ = P / S = P / f(h)

[0139] Controlling the power density ρ of the laser irradiation area is crucial during the restoration process. The power density ρ is related to the laser power P and the laser spot area S, where ρ = P / S, and the unit is W / mm². 2 The linear laser emitted by the laser diverges linearly along a certain direction, meaning the laser spot area S is linearly related to the laser irradiation distance h between the sample and the laser output port; that is, the spot area S is a linear function of the laser irradiation distance h. The spot area S is represented by a linear function f(h) with respect to distance h, i.e., S = f(h). The power density ρ = P / S, therefore, the power density ρ is related to the distance, and the expression can be further transformed into ρ = P / S = P / f(h). To control a suitable power density ρ, it is necessary to first obtain the function f(h) of the spot area S with respect to distance h. This yields the relationship between power density ρ and laser irradiation distance h: ρ = P / S = P / f(h). The power density ρ is precisely controlled by the distance h, and the laser irradiation distance h is selected based on the chosen power density.

[0140] This embodiment describes a method for restoring lead content in murals and painted artifacts using laser photodynamic therapy. The linear laser is mounted on a laser fixture on an adjustable laser stand and connected to a 220V 50Hz AC power supply.

[0141] The restoration power density ρ is the laser power density for mural restoration. b , ρ b =P b / S b The unit is W / mm 2 In the formula, P b For the laser power of mural restoration, S b The area of ​​the laser spot used for mural restoration.

[0142] S b =f(h b ); h in the formula b This refers to the laser irradiation distance between the laser output port and the simulated sample during the restoration of murals and painted cultural relics.

[0143] Therefore ρ b =P b / S b =P b / f(hb )

[0144] Determining the laser power density ρ for the restoration of calligraphy, paintings, and colored cultural relics b initial value ρ b0 The value is 1.50~2.24W / mm. 2 .

[0145] In determining the repair laser power density ρ b At that time, the laser power P was measured by a power meter. b Perform f(h) b ) measurement, the f(h b ) is the area S of the light spot. b With distance h b The function;

[0146] In performing f(h) b During measurement, let the lateral length of the laser spot be x and the longitudinal width be y, therefore the area of ​​the laser S = x·y. When the distance h between the laser outlet and the simulated sample takes different values, the corresponding lateral length x and longitudinal width y of the laser spot are measured respectively.

[0147] Turn on the linear laser and directly measure the laser power P using a power meter. b 1.12W. Perform f(h) b The measurement method is as follows: Let the horizontal length of the laser spot be x, and the vertical width be y, then the area S of the laser is... b =x*y. When the laser irradiation distance is h b When different values ​​are taken, the lateral length x and longitudinal width y of the corresponding laser spot are measured respectively. The results show that when the laser irradiation distance h is taken, the laser spot is irradiated at a distance of 1000 meters. b When the diameters are 20mm, 30mm, 40mm, 50mm, and 60mm, the corresponding transverse lengths x are 18mm, 26mm, 34mm, 42mm, and 50mm, respectively; and the corresponding longitudinal widths y are 1mm, 1mm, 1mm, 1mm, and 1mm, respectively. This indicates that the laser emitted by the laser diverges linearly along the transverse direction of the laser spot, while remaining constant in the longitudinal direction of the laser spot.

[0148] The laser irradiation distance h b By performing a linear fit on the corresponding horizontal length x, we can obtain the horizontal width x and the laser irradiation distance h. b The fitting relationship is x=g(h) b Furthermore, the longitudinal width y does not change with the laser irradiation distance h. b The variation is kept constant at 1 mm. The area S of the light spot is obtained. b =x×y=g(h bThe area S is obtained by multiplying the light spot area by 1 mm. b As the laser irradiation distance h b linear function S b S b =f(h b )=g(h b The relationship between the repair power density and distance is obtained by multiplying ρ by 1 mm. b =P b / S b =P b / f(h b ).

[0149] The relationship between the repair laser power density and distance is expressed by the formula ρ. b =P b / S b =P b / f(h b Adjust the laser irradiation distance h by rotating the bracket knob. b To achieve the change in repair laser power density ρ b This allows for the simulation of different repair laser power densities ρ. b The repair effect was observed. Results showed that when the repair laser power density was 1.50~2.24 W / mm², the repair was most effective. 2 At this time, catalytic porphyrin produces singlet oxygen without damaging the paper.

[0150] Step 3, Safety verification of power density in the laser irradiation area:

[0151] To verify the safety of the power density used for repairing the selected laser irradiation area, a simulated sample was prepared for testing and verification.

[0152] The substrate of the simulated mural artifact is the same as that of the mural artifact, and black lead sulfide is applied to the surface of the substrate until the surface is completely black.

[0153] Verification of laser power density ρ for the restoration of murals and painted cultural relics b The specific process of security is as follows:

[0154] The initial value ρ of the repair laser power density b0 =1.50~2.24W / mm 2 The values ​​in the table are used as the initial repair power density for safety verification; the distance between the laser output port and the simulated sample is used as the initial laser irradiation distance h for safety verification. b0 The initial value ρ of the repair laser power density is then sequentially adjusted. b0 The simulated sample was irradiated with laser for 10 minutes, and the irradiated area was checked for yellowing or discoloration, which are caused by burning or ablation.

[0155] If the simulated sample does not turn yellow, it indicates that the repair process is safe and without damage. Therefore, the initial repair power density ρ is verified based on the current safety profile. b0 As the repair power density ρ b The laser irradiation distance h between the current laser output port and the simulated sample is... b0 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. b .

[0156] If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance h should be increased. b Each time the laser irradiation distance is increased by 1mm, a new laser irradiation distance h is obtained. b1 The new relationship between power density and laser irradiation distance ρ b1 =P b / S b =P b / f(h b1 ).

[0157] Using the new power density ρ again b1 Irradiate the simulated sample with a laser for 10 minutes. Observe whether the surface of the simulated sample shows yellowing or discoloration due to burning or ablation. If the simulated sample does not show yellowing, then apply the current repair power density ρ. b1 As the repair power density ρ b The laser irradiation distance h between the current laser output port and the simulated sample is... b1 The laser irradiation distance h between the laser output port and the simulated sample during the repair process. b If the simulated sample turns yellow or discolored due to burning or ablation, the laser irradiation distance is increased by 1 mm to obtain the new laser irradiation distance h. b2 The new relationship between power density and laser irradiation distance ρ b2 =P b / S b =P b / f(h b2 ).

[0158] Repeat the process of irradiating the simulated sample with a new repair power density, observing whether burning or ablation occurs on the surface of the simulated sample, and then continuing to increase the laser irradiation distance h. b The process continues until the simulated sample surface shows no yellowing or discoloration due to burning or ablation. At the current repair power density ρ bn The power density ρ of the restoration of this mural-painted cultural relic b The laser irradiation distance h between the current laser output port and the simulated sample is... bnThe laser irradiation distance h, which is the painted artifact of this mural, is... b .

[0159] Step 4, Lead restoration of mural-painted artifacts:

[0160] When restoring painted and colored cultural relics to lead, the determined restoration power density and laser irradiation distance of the laser are used as the power density for lead restoration and the laser irradiation distance between the laser output port and the simulated sample.

[0161] Based on the comprehensive evaluation index △E of the color difference between each area to be repaired on the surface of the painted cultural relic and the lead white standard sample, the concentration of porphyrin solution and the laser irradiation time used for each area to be repaired were determined.

[0162] The areas to be repaired were repeatedly repaired in sequence to complete the lead restoration of the painted cultural relic surface.

[0163] When performing lead-based restoration on painted murals, if the overall color difference assessment index ΔE between the area to be restored and the lead white standard sample is 5, the porphyrin solution concentration is 10 mg / L and the laser irradiation time is 5 min. Based on this, for every increase of 1 in the overall color difference assessment index ΔE between the area to be restored and the lead white standard sample, the porphyrin solution concentration increases by 0.125 mg / L and the irradiation time increases by 5 s.

[0164] The specific process of sequentially repairing each area on the surface of the painted cultural relic is as follows:

[0165] I. Repair of the first area to be repaired.

[0166] The first area to be repaired was treated using a method of repeated irradiation and multiple repairs. Specifically:

[0167] i. First repair of the first area to be repaired. Measure and record the color difference ΔE between the first area to be repaired and the lead white standard sample, and determine the concentration of the porphyrin solution and the laser irradiation time.

[0168] The porphyrin solution is sprayed onto the surface of the first area to be repaired according to the determined concentration, thus wetting the area. The surface of the first area to be repaired, coated with the porphyrin solution, is then irradiated with a laser. After irradiation, the laser is turned off, completing the first stage of lead repainting repair on the first area to be repaired.

[0169] ii. Second repair of the first area to be repaired. Restore the position of the laser. Position the laser output port directly towards the first area to be repaired after the first repair; remeasure the color difference comprehensive evaluation index ΔE between the first area to be repaired and the lead white standard sample to obtain a new color difference value; based on the new color difference value, determine the required concentration of porphyrin solution and the laser irradiation time to obtain the required porphyrin solution concentration and laser irradiation time for the second repair of the first area to be repaired.

[0170] Weigh out the porphyrin solution and spray it onto the surface of the first area to be repaired, which has already undergone the first repair. Then, irradiate the surface of this first area with the porphyrin solution sprayed on it using a laser. This completes the second repair of the lead-returning repair on the first area to be repaired.

[0171] iii. Repair the remaining areas of the first repair area. Repeat the second repair process for the first repair area, sequentially completing the remaining repairs of the first repair area based on the current color difference assessment index ΔE between the first repair area and the lead white standard sample, the determined concentration of the required porphyrin solution, and the determined laser irradiation time, until the difference between the measured color difference assessment index ΔE with the lead white standard sample and the measured color difference assessment index ΔE obtained in the previous repair is less than 1. The repair of the first repair area is then complete.

[0172] II. Repair of the second area to be repaired

[0173] i. Adjust the platform position to move the laser spot to the next area to be repaired. Repeat the process of repairing the first area to be repaired. Based on the comprehensive evaluation index ΔE of the color difference between the current area to be repaired and the lead white standard sample, the determined concentration of the current porphyrin solution, and the determined current laser irradiation time, complete each repair step for the second area to be repaired.

[0174] ii. Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired to complete the repair of the second area to be repaired.

[0175] III. Repair of the remaining areas to be repaired

[0176] Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired, until all areas to be repaired are repaired, thus completing the lead restoration work on the surface of the painted cultural relic.

[0177] Step 5, put away the artifacts:

[0178] After the restoration is completed, the restored murals and painted artifacts will be left to dry at room temperature before being collected and preserved.

Claims

1. A method for removing lead residue from colored paintings using laser photodynamic therapy, characterized in that, This includes removing lead residue from the surface of painted and colored calligraphy and paintings on Xuan paper, as well as from the painted murals. The specific process is as follows: Step 1: Identify the areas on the surface of the artifact that require restoration. The adjustable laser support is placed on a horizontal platform; the surface of the artifact to be restored is divided into multiple blocks; each block is measured sequentially using a colorimeter, and the color difference between each block and the lead white standard sample is obtained as a comprehensive evaluation index △E. For calligraphy and painting artifacts made of Xuan paper, the area with △E≥5 is taken as the area to be repaired on the surface of the calligraphy and painting artifact made of Xuan paper. For mural and painted cultural relics, the area with △E≥5 is taken as the area to be repaired on the surface of the mural and painted cultural relics. Step 2, determine the laser power density for the area to be repaired: The relationship between laser power density and laser irradiation distance for the restoration of painted cultural relics is ρ=P / S=P / f(h); the units are W / mm². 2 ; The laser irradiation conditions include the repair laser power density ρ, the laser spot area S, the laser irradiation distance h, and the laser power P; wherein S=f(h); the laser irradiation distance h is the distance between the laser output port and the simulated sample of the calligraphy and painting cultural relic made of Xuan paper or the simulated sample of the mural and painted cultural relic. The laser power density ρ used for restoration includes the laser power density ρ for the restoration of calligraphy and painting artifacts made of Xuan paper. z Laser power density ρ for the restoration of murals and painted cultural relics b The laser spot area S includes the laser spot area S for the restoration of calligraphy, paintings, and cultural relics on Xuan paper. z The area of ​​light spots during the restoration of murals and painted cultural relics (S) b The laser irradiation distance h includes the laser irradiation distance h for the restoration of calligraphy, paintings, and colored cultural relics made of Xuan paper. z Laser irradiation distance h for mural and painted cultural relic restoration b Laser power P includes the laser power P for the restoration of calligraphy, paintings, and colored cultural relics made of Xuan paper. z Laser power P for the restoration of murals and painted cultural relics b ; Laser power density ρ for the restoration of calligraphy, paintings, and colored cultural relics on Xuan paper z 1.2~2.0W / mm 2 Laser power density ρ for the restoration of murals and painted cultural relics b The value is 1.50~2.24W / mm. 2 ; Step 3, Safety verification of laser power density for repairing the laser irradiated area: Safety verification was performed on the selected laser power density for restoration; simulated samples of calligraphy and painting artifacts and mural artifacts made of Xuan paper were prepared for testing and verification; When verifying the safety of calligraphy, paintings, and colored cultural relics made of Xuan paper: A simulated sample of calligraphy and painting artifacts made of Xuan paper was irradiated with a laser to observe whether there was any burning or ablation damage on the surface of the simulated sample. If the simulated sample of calligraphy and painting artifacts made of Xuan paper was undamaged, the initial repair laser power density ρ was used to verify safety. zn The laser power density ρ of the surface of calligraphy and painting artifacts made of Xuan paper that need to be restored z The laser irradiation distance h between the laser output port of the current restoration laser and the simulated sample of calligraphy and painting cultural relics made of Xuan paper is used. zn The laser irradiation distance h between the laser output port and the painted calligraphy and painting artifacts made of Xuan paper during restoration. z If the simulated cultural relic sample made of Xuan paper with calligraphy and painting is damaged, then the laser irradiation distance h is adjusted. zn This allows for the acquisition of a new repair laser power density until the simulated cultural relic sample made of Xuan paper is undamaged, and the laser irradiation distance h is used as the current laser irradiation distance. zn The laser irradiation distance h between the laser output port and the painted calligraphy and painting artifacts made of Xuan paper during restoration. z To repair laser power density ρ zn The laser power density ρ of the surface of calligraphy and painting artifacts made of Xuan paper that need to be restored z ; When verifying the safety of mural-painted cultural relics: The simulated sample of the mural-painted cultural relic was irradiated with a laser, and the surface of the simulated sample was observed to show any burning or ablation damage. If the simulated sample of the mural-painted cultural relic was undamaged, the initial restoration laser power density ρ was used to verify safety. bn Laser power density ρ for the surface of mural-painted cultural relics awaiting restoration b The laser irradiation distance h between the laser output port and the simulated mural painting artifact sample is... bn The distance h between the laser output port and the painted mural artifact during restoration. b If the simulated mural artifact is damaged, the laser irradiation distance h is adjusted. bn This allows for the acquisition of a new laser power density for restoration, continuing until the simulated sample of the mural is undamaged, and using the current laser irradiation distance h. bn The distance h between the laser output port and the painted mural artifact during restoration. b To repair laser power density ρ bn Laser power density ρ for the surface of mural-painted cultural relics awaiting restoration b ; Step 4, Lead restoration of painted cultural relics: The lead restoration includes painted and mural artifacts made of Xuan paper. When performing lead restoration on Xuan paper-based calligraphy, painting, or mural artifacts, the laser power density and laser irradiation distance of the laser are determined as the laser power density and laser irradiation distance between the laser output port and the Xuan paper-based calligraphy, painting, or mural artifact. Based on the comprehensive evaluation index △E of the color difference between each area to be restored and the lead white standard sample of the Xuan paper-based calligraphy and painting cultural relics or murals, the concentration of porphyrin solution and the laser irradiation time used for each area to be restored are determined. The repair process is repeated on each area to be repaired to complete the lead restoration of the surface of the Xuan paper-based calligraphy and painting artifacts or mural artifacts. Step 5, rewind: After restoration, place the calligraphy, painting, or mural artifacts made of Xuan paper at room temperature until the surface is dry, then roll them up and store them.

2. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, The specific process for determining the repair laser power density of the area to be repaired is as follows: When determining the laser power density ρ for the area to be repaired, the laser power P is measured by a power meter; f(h) is measured, where f(h) is a function of the spot area S and the distance h; The process of measuring f(h) is as follows: let the horizontal length of the laser spot be x and the vertical width be y, so the area of ​​the laser S = xy; when the distance h between the laser outlet and the simulated sample of calligraphy and painting on Xuan paper or the simulated sample of mural painting takes different values, the horizontal length x and the vertical width y of the corresponding laser spot are measured respectively.

3. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, The simulated sample of the calligraphy and painting artifacts made of Xuan paper uses raw Xuan paper of the same type as the calligraphy and painting artifacts made of Xuan paper, and the surface is coated with black lead sulfide until the surface turns completely black. The substrate of the simulated mural artifact is the same as that of the mural artifact, and black lead sulfide is coated on the surface of the substrate until the surface is completely black.

4. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, When restoring calligraphy and painted cultural relics made of Xuan paper, the laser power density ρ of the restoration was verified. z The specific process of ensuring security is as follows: To repair the initial value ρ of the laser power density z0 =1.2~2.0W / mm 2 The values ​​in the table are used as the initial repair laser power density for safety verification; the distance between the laser output port and the simulated sample of calligraphy and painting cultural relics made of Xuan paper is used as the initial laser irradiation distance h for safety verification. z0 ; sequentially according to the initial value ρ of the repair laser power density z0 The simulated cultural relics samples made of Xuan paper were irradiated with laser for 10 minutes, and the irradiated parts were tested to see if yellowing or discoloration caused by burning or ablation occurred. If the initial value of the repair laser power density ρ is given in each of the aforementioned repair laser power densities z0 The simulated cultural relic sample made of Xuan paper, featuring calligraphy and painting, does not yellow, indicating that the restoration process is safe and without damage. Therefore, the initial restoration laser power density ρ is used to verify the safety of the process. z0 The laser power density ρ of the surface of calligraphy and painting artifacts made of Xuan paper that need to be restored z The laser irradiation distance h between the laser output port and the simulated sample of calligraphy and painting cultural relics made of Xuan paper is used to determine the laser irradiation distance. z0 The laser irradiation distance h between the laser output port and the painted calligraphy and painting artifacts made of Xuan paper during restoration. z ; If the simulated cultural relic sample made of Xuan paper exhibits yellowing or discoloration due to burning or ablation, the laser irradiation distance h should be increased. z Each time the laser irradiation distance is increased by 1mm, a new laser irradiation distance h is obtained. z1 The new formula for the relationship between the repair laser power density and the laser irradiation distance is ρ. z1 =P z / S z =P z / f(h z1 ); Using the new repair laser power density ρ again z1 Irradiate the simulated cultural relic sample made of Xuan paper with calligraphy and painting for 5 minutes using laser; observe whether the surface of the simulated cultural relic sample shows yellowing or discoloration due to burning or ablation; if the simulated cultural relic sample made of Xuan paper does not show yellowing, then the current restoration laser power density ρ is used. z1 As a repair laser power density ρ z The laser irradiation distance h between the laser output port and the simulated sample of calligraphy and painting cultural relics made of Xuan paper is used to determine the laser irradiation distance. z1 The laser irradiation distance h during repair z If the simulated cultural relic sample made of Xuan paper shows yellowing or discoloration due to burning or ablation, the laser irradiation distance will be further increased; the increased laser irradiation distance is 1mm, resulting in a new laser irradiation distance h. z2 The new formula for the relationship between the repair laser power density and the laser irradiation distance is ρ. z2 =P z / S z =P z / f(h z2 ); Repeat the process of irradiating the simulated Xuan paper calligraphy and painting artifact with the new restoration laser power density, observing whether the surface of the simulated sample shows yellowing or discoloration due to burning or ablation, and continuing to increase the laser irradiation distance until the surface of the simulated Xuan paper calligraphy and painting artifact no longer shows yellowing or discoloration due to burning or ablation, and determine the current restoration laser power density ρ. zn Laser power density ρ for the restoration of calligraphy and painting artifacts made of Xuan paper z Determine the laser irradiation distance h between the current laser output port and the simulated sample of calligraphy and painting on Xuan paper. zn h is the laser irradiation distance between the laser emitter and the painted or colored cultural relic made of Xuan paper. z .

5. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, When restoring murals and painted artifacts, the laser power density ρ used for restoration of these artifacts was verified. b The specific process of ensuring security is as follows: To repair the initial value ρ of the laser power density b0 =1.50~2.24W / mm 2 The values ​​in the table are used as the initial laser power density for safety verification; the distance between the laser output port and the simulated mural painting artifact sample is used as the initial laser irradiation distance h for safety verification. b0 ; sequentially according to the initial value ρ of the repair laser power density b0 The simulated samples of the mural painted cultural relics were laser-irradiated for 10 minutes, and the irradiated areas were tested to see if yellowing or discoloration occurred due to burning or ablation. If the simulated sample of the mural painting does not yellow, it indicates that the restoration process is safe and without damage. Therefore, the initial restoration laser power density ρ will be used to verify the safety of the restoration process. b0 As a repair laser power density ρ b The laser irradiation distance h between the current laser output port and the simulated sample of the mural painted artifact is... b0 The laser irradiation distance h between the laser output port and the mural / painted artifact during restoration. b ; If the simulated sample of the mural artifact shows yellowing or discoloration due to burning or ablation, then the laser irradiation distance h should be increased. b Each time the laser irradiation distance is increased by 1mm, a new laser irradiation distance h is obtained. b1 The new formula for the relationship between the repair laser power density and the laser irradiation distance is ρ. b1 =P b / S b =P b / f(h b1 ); Using the new repair laser power density ρ again b1 Irradiate the simulated mural-painted artifact sample with laser for 10 minutes; observe whether the surface of the simulated mural-painted artifact sample shows yellowing or discoloration due to burning or ablation; if the simulated mural-painted artifact sample does not show yellowing, then the current restoration laser power density ρ will be used. b1 As a repair laser power density ρ b The laser irradiation distance h between the laser output port and the simulated mural painting artifact sample is... b1 The distance h between the laser output port and the painted mural artifact during restoration. b If the simulated sample of the mural exhibits yellowing or discoloration due to burning or ablation, the laser irradiation distance is further increased; the increased distance is 1 mm, resulting in a new laser irradiation distance h. b2 The new formula for the relationship between the repair laser power density and the laser irradiation distance is ρ. b2 =P b / S b =P b / f(h b2 ); Repeat the process of irradiating the simulated mural painting artifact sample with the new restoration laser power density—observe whether yellowing or discoloration occurs on the surface of the simulated mural painting artifact sample due to burning or ablation—continue to increase the laser irradiation distance h. b The process continues until the surface of the simulated sample of the mural's painted artifact shows no yellowing or discoloration caused by burning or erosion; using the current restoration laser power density ρ bn The laser power density ρ used for the restoration of this mural-painted artifact b The laser irradiation distance h between the laser output port and the simulated mural painting artifact sample is... bn The laser irradiation distance h, which is the painted artifact of this mural, is... b .

6. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, When performing lead restoration on painted murals, the porphyrin solution concentration is 5 mg / L and the laser irradiation time is 3 min when the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample is 5. Based on this, for every increase of 1 in the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample, the porphyrin solution concentration is increased by 0.125 mg / L and the irradiation time is increased by 3 s. When performing lead restoration on painted murals, the porphyrin solution concentration is 10 mg / L and the laser irradiation time is 5 when the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample is 5. Based on this, for every increase of 1 in the comprehensive evaluation index ΔE of the color difference between the area to be restored and the lead white standard sample, the porphyrin solution concentration is increased by 0.125 mg / L and the irradiation time is increased by 5 seconds.

7. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, The specific process for repairing each area of ​​the painted cultural relic's surface in sequence is as follows: Ⅰ Repair of the first area to be repaired; The first area to be repaired was repaired using a method of repeated irradiation and multiple repairs; specifically: i. First repair of the first area to be repaired; measure and record the color difference comprehensive evaluation index △E between the first area to be repaired and the lead white standard sample, and determine the concentration of the porphyrin solution and the laser irradiation time; The porphyrin solution is sprayed onto the surface of the first area to be repaired according to the determined porphyrin solution concentration, so that the first area to be repaired is wetted by the porphyrin solution. The surface of the first area to be repaired, which was sprayed with porphyrin solution, was irradiated with a laser; after the irradiation was completed, the laser was turned off, and the first repair of the lead-returning repair of the first area to be repaired was completed. ii. Second repair of the first area to be repaired; restoration of the laser's position; Position the laser output port directly over the first area to be repaired after the first repair; remeasure the color difference comprehensive evaluation index ΔE between the first area to be repaired and the lead white standard sample to obtain a new color difference value; based on the new color difference value, determine the required concentration of porphyrin solution and the laser irradiation time to obtain the required concentration of porphyrin solution and laser irradiation time for the second repair of the first area to be repaired. Weigh out the porphyrin solution and spray it onto the surface of the first area to be repaired after the first repair. The surface of the first area to be repaired, which was sprayed with porphyrin solution, was irradiated with laser; this completed the second repair of the lead-returning repair of the first area to be repaired. iii. Repair the remaining areas of the first area to be repaired; repeat the second repair process of the first area to be repaired, and based on the current color difference comprehensive evaluation index △E of the first area to be repaired, the determined concentration of the porphyrin solution and the determined laser irradiation time, complete the remaining repairs of the first area to be repaired in sequence until the current color difference comprehensive evaluation index △E of the first area to be repaired is ≤2; complete the repair of the first area to be repaired. II. Repair of the second area to be repaired i. Adjust the platform position to move the laser spot to the next area to be repaired; repeat the process of repairing the first area to be repaired, and complete each repair of the second area to be repaired based on the color difference comprehensive evaluation index △E of the lead white standard sample of the current area to be repaired, the current concentration of the porphyrin solution, and the current laser irradiation time. ii. Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired to complete the repair of the second area to be repaired; III. Repair of the remaining areas to be repaired Repeat the process of the first repair of the first area to be repaired, the second repair of the first area to be repaired, and the remaining repairs of the first area to be repaired, until all areas to be repaired are repaired, thus completing the lead restoration work on the surface of the painted cultural relic.

8. The method for removing lead residue from colored paintings using laser photodynamic therapy as described in claim 1, characterized in that, The laser used for laser photodynamic removal of lead residue from colored paintings is a semiconductor continuous laser with a center wavelength of 650nm, and the room temperature during the repair process is 20℃. When restoring painted murals and artifacts by removing lead, the maximum power P of the laser is 2.24W; when restoring painted murals and artifacts by removing lead, the maximum power P of the laser is 2.2W.

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