Method for removing mildew spots on back coating of mildewed black-and-white photographic negative film and application

Abstract

The invention belongs to the technical field of file repair and protection, and relates to a method for removing mildew spots on a back coating of a mildewed black-and-white photographic negative film and application. The removal method comprises the following steps: S1, dedusting, cleaning and airing the mildewed black-and-white photographic negative film to complete pretreatment; s2, coating an ethyl cellulose solution on an emulsion layer of the pretreated mildewed black-and-white photographic negative to naturally form a film so as to protect the emulsion layer; and S3, further smearing a proteolytic enzyme solution on the back coating surface of the mildewed black-and-white photographic negative film, and after reaction for 20-30 minutes, cleaning and airing to obtain the mildewed black-and-white photographic negative film. The method disclosed by the invention can be used for mildly removing mould bred on the back coating of the negative film and is good in safety; the growth environment of mould can be destroyed, so that mould relapse is prevented.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of archive repair and protection, and relates to a method for removing mold spots on a back coating layer of a moldy black-and-white photographic film and application. BACKGROUND

[0002] Compared with traditional paper archives in the form of character symbols, the photographic image archives can more intuitively and accurately record historical scenes and social features, and become indispensable visualized historical material carriers for studying historical culture. As a kind of photographic image archive with a large quantity and outstanding value in the archive collection, the black-and-white photographic film is an important part of the archive resource system with great research value. Since the black-and-white photographic film contains gelatin in its structure, it is easy to become a breeding ground for mold during the storage process. In addition, the loose network structure formed by the growth of mold and the rough surface formed after the decomposition of gelatin by mold; when visible light contacts the rough surface, scattering occurs, which not only causes the reflectivity to rise, but also causes the visible light transmittance of the low-density area of the film image to decrease, and mold spots appear on the black-and-white photo developed from the film, which destroys the picture clarity, blurs the valuable image details, and finally causes the image distortion of the black-and-white photo during the development or scanning process. Therefore, it is necessary to remove the mold spots on the moldy black-and-white photographic film.

[0003] Referring to the patent document with the publication number CN102205328A, a method for removing old mold spots on the base layer of a black-and-white film is disclosed, which uses a sodium hypochlorite aqueous solution as a remover to corrode and remove the mold spots on the base layer, and then uses ascorbic acid to reduce and eliminate the excess sodium hypochlorite. However, this method is relatively complicated and needs to be repeatedly applied and wiped. More importantly, sodium hypochlorite has strong corrosiveness, and if not handled properly, the emulsion layer can be eroded. At the same time, the solution is also corrosive to the skin of the operator, and the operator needs to take protective measures to ensure safety.

[0004] Referring to the Chinese patent document with the publication number CN104927489B, a black-and-white photographic film emulsion layer mold spot masking agent is disclosed, which uses bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate to penetrate into the mold spots on the emulsion layer of the moldy black-and-white photographic film, then uses n-butanol to clean and remove the excess bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and finally applies the black-and-white film emulsion layer mold spot masking agent until the organic solvent is completely volatilized, and a thin film is formed on the film emulsion layer by the ethyl cellulose solution and bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, which weakens the influence of the mold spots on the recorded image of the film and restores the original appearance of the recorded image of the film. However, this method has limited treatment effect on severely moldy films, and the operation process is relatively complex, which requires accurate control of the concentration of reagents and the operation process. SUMMARY

[0005] The application provides a method for removing mold spots on a back coating layer of a moldy black-and-white photographic film and application.

[0006] In order to achieve the above object, the technical scheme adopted by the application is:

[0007] A method for removing mold spots on a back coating layer of a moldy black-and-white photographic film, comprising the following steps:

[0008] S1, dust removal, cleaning and air drying of the moldy black-and-white photographic film are performed to complete pretreatment;

[0009] S2, ethyl cellulose solution is applied to the emulsion layer of the pretreated moldy black-and-white photographic film to form a protective film naturally;

[0010] S3, further, proteinase solution is applied to the back coating layer of the moldy black-and-white photographic film after step S2, and after reaction for 20-30 minutes, cleaning, air drying are performed to complete the method.

[0011] Further, in step S1, dust removal is performed by wiping off floating dust with a cotton soft towel; and cleaning is performed with n-butanol.

[0012] Further, in step S2, the concentration of the ethyl cellulose solution is 5±0.5%.

[0013] Further, in step S3, the proteinase solution is first dropped on an absorbent paper; and then the absorbent paper is attached to the surface of the back coating layer of the moldy black-and-white photographic film.

[0014] Further, in step S3, cleaning is performed with n-butanol solution.

[0015] The concentration of the proteinase solution is 5±0.5%; and the proteinase solution is an animal proteinase solution or a plant proteinase solution.

[0016] Application of an animal proteinase in removing mold spots on a back coating layer of a moldy black-and-white photographic film.

[0017] Further, in the application, the animal proteinase solution is first dropped on an absorbent paper; and then the absorbent paper is attached to the surface of the back coating layer of the moldy black-and-white photographic film.

[0018] Further, before the absorbent paper is attached to the surface of the back coating layer of the moldy black-and-white photographic film, the following treatment is further required for the moldy black-and-white photographic film:

[0019] The mildewed black-and-white photographic film is dusted, cleaned and dried, and then ethyl cellulose solution is applied to the emulsion layer of the mildewed black-and-white photographic film to form a natural film.

[0020] With further limitation, the concentration of the protease solution is 5±0.5%; the protease solution is an animal protease solution or a plant protease solution; and the concentration of the ethyl cellulose solution is 5±0.5%.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1. The protease solution is selected as the mildew stain remover in the present application. The protease can break the peptide bond (i.e. C-N bond) in the protein, thereby hydrolyzing it. The protease solution is uniformly applied to the surface of the back coating layer of the mildewed black-and-white photographic film. The protease has a specific decomposition effect on the protein of the mildew fungus, and simultaneously selectively degrades the mildew fungus and the gelatin layer rich in nutrients on the surface of the black-and-white photographic film. This not only exposes the base layer of the black-and-white photographic film and gently removes the mildew stains growing on the back coating layer of the black-and-white photographic film, but also destroys the nutrient supply system required for the growth of the mildew fungus. The growth environment of the mildew fungus is destroyed, so that the subsequent mildew fungus is difficult to colonize and reproduce due to the lack of carbon and nitrogen sources and other nutrients provided by the gelatin matrix, thereby constructing a protective mechanism for inhibiting the growth of mildew on the surface of the base, preventing the recurrence of mildew, and achieving a long-term mildew prevention effect.

[0023] 2. The experimental verification shows that the removal method of the present application can effectively restore the optical transmittance of the black-and-white photographic film after processing, so that visible light can normally penetrate the black-and-white photographic film during scanning and printing, thereby restoring the image information recorded by the mildewed black-and-white photographic film. This shows that the removal method of the present application has feasibility for removing mildew stains.

[0024] 3. The protease is used to remove the mildew stains in the present application. The processing process does not introduce irreversible chemical changes. The residual removal reagent can be completely removed by cooperating with the subsequent cleaning process (such as dust-free paper adsorption and petroleum ether wiping), so that the black-and-white photographic film can be restored to the original state, which meets the requirements of material safety for cultural relic restoration. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the image recovery effect of the back coating layer of the mildewed black-and-white photographic film in Example 1;

[0026] Figure 2 is the surface micro-morphology diagram of the mildewed black-and-white photographic film before and after removing the mildew stains in Example 1;

[0027] Figure 3 is the surface morphology and surface roughness of the mildewed black-and-white photographic film before and after removing the mildew stains in Example 1;

[0028] Figure 4 is the surface reflectivity of the moldy black and white photographic film before and after mold spots are removed in Example 1;

[0029] Figure 5 is the infrared spectrum of the surface of the moldy black and white photographic film before and after mold spots are removed in Example 1. DETAILED DESCRIPTION

[0030] The present application will be further described in conjunction with the accompanying drawings and examples, but the embodiments of the present application are not limited thereto. Other methods for preparing the compounds of the present application are considered to be within the scope of the present application, with some routine modifications of the reaction conditions according to the present application.

[0031] Unless otherwise defined, technical or scientific terms used in the present application shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0032] It should also be understood that the above-described embodiments are merely intended to explain the present application, and the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent substitutions or changes to the technical solutions and inventive concepts of the present application within the technical scope disclosed by the present application, which should be encompassed within the protection scope of the present application.

[0033] Example 1

[0034] The present embodiment provides a mold spot removal method for the back coating layer of a moldy black and white photographic film, comprising the following steps:

[0035] S1, wiping off the surface dust of the moldy black and white photographic film with a cotton-soft cloth;

[0036] S2, further cleaning the surface of the moldy film with n-butanol, and placing it in a ventilated place for natural drying;

[0037] S3, after the film is completely dried, recording the film state and image information before the mold spots are removed by using a scanner;

[0038] S4, placing the film flat on a clean and flat experimental table, using a plastic dropper to suck the ethyl cellulose solution (concentration 5±0.5%), and dropping it on the surface of the film emulsion layer, and then using a cotton swab to smear it evenly, and then placing it in a ventilated place for natural film formation; preferably, the ethyl cellulose solution is formed by dissolving ethyl cellulose in n-butanol solution;

[0039] S5, after natural film formation, fixing the dried film on a glass plate with a traceless adhesive tape, with the back coating layer facing up;

[0040] S6, animal proteinase solution (concentration 5±0.5%) is taken with a plastic dropper and dropped on the water absorption paper, and then the water absorption paper is attached to the surface of the back coating layer of the negative film, and the reaction is allowed to proceed for 30 min; the reaction time can also be 20 min or 25 min.

[0041] S7, the surface of the negative film is cleaned with n-butanol solution, mainly to remove the ethyl cellulose film and the residual proteinase solution; and the negative film is naturally dried in a ventilated place;

[0042] S8, after the negative film is completely dried, the mold spot removal is completed.

[0043] In this embodiment, the state and image information of the negative film after the mold spot removal are recorded by a scanner, so as to judge the removal effect.

[0044] Example 2

[0045] This embodiment provides a mold spot removal method for moldy black and white photographic film back coating layer, which refers to Example 1; and the difference from Example 1 is that a plant proteinase solution is used.

[0046] The proteinases used in the above examples are animal proteinase and plant proteinase produced by Hefei Qiansheng Biological Technology Co., Ltd.

[0047] Example 3

[0048] This embodiment provides an application of proteinase in removing mold spots on moldy black and white photographic film back coating layer. The specific process of the application can refer to the specific operation steps of Example 1 or Example 2.

[0049] In order to illustrate the beneficial effects of the technical scheme of the present application, the black and white photographic film before and after the mold spot removal in Example 1 is analyzed by using a scanner, a tungsten filament scanning electron microscope, a laser confocal microscope, an ultraviolet near-infrared spectrophotometer, a mid-infrared-far-infrared spectrum instrument, and the specific test results are as follows:

[0050] Test 1

[0051] The black and white photographic film before and after the mold spot treatment in Example 1 is scanned by using an Epson Perfection V850Pro scanner, and the negative film image recovery effect is obtained; for details, see Figure 1 .

[0052] Among them, Figure 1 a presents the scanning state of the black and white photographic film back coating layer after mold growth, and it can be seen that the mold adheres to the surface of the back coating layer, forming a white irregular spot structure. This structure blocks the transmission of light, interferes with the transmission of light through the negative film, and further affects the printing clarity of the negative film. Figure 1 b, Figure 1c are the positive and negative images of the moldy film scanning, the mold spot prevents the transmission of light, causing the film information in the blocked area to appear fuzzy. Figure 1 d is the scanning image of the black and white photographic film after removing the mold spot on the back coating layer, and Figure 1 a can be seen that after the mold spot removal treatment, the film surface is clean and smooth, the light can normally pass through, and the real state of the film printing can be restored. Figure 1 e, Figure 1 f are the positive and negative images of the film scanning after removing the mold spot, compared with Figure 1 b, Figure 1 c, after removing the mold spot, the image information can be clearly restored, and the original image quality of the film can be effectively restored.

[0053] Test 2

[0054] Figure 2 is the microscopic morphology of the black and white photographic film back coating layer before and after removing the mold spot in Example 1.

[0055] As can be seen from Figure 2 , Figure 2 a is the surface morphology of the black and white photographic film before removing the mold spot, the surface presents a complex network, granular structure, which is the microscopic morphology of mold spores, etc., indicating that the mold grows and reproduces on the film surface in large quantities, forming a dense microbial community structure, which will erode and contaminate the film material. Figure 2 b is the surface morphology after removing the mold spot, the surface is relatively flat and simple, and the original mold microscopic structure basically disappears, indicating that the mold spot removal measure is effective, and the film surface is restored to a relatively clean state, reducing the adverse effects of mold on the film.

[0056] Test 3

[0057] Figure 3 is the surface roughness and surface morphology observation of the black and white photographic film back coating layer before and after removing the mold spot in Example 1 by laser confocal scanning microscope. Among them: Figure 3 a is the two-dimensional morphology of the film surface, the mold grows in a disordered network structure on the film surface, and the corresponding three-dimensional morphology is shown in Figure 3 b, yellow is the surface protrusion area, blue is the surface depression area, quantitative analysis shows that the arithmetic mean height (Sa) of the moldy film surface is 0.54 μm, the maximum height difference (Sz) is 12.77 μm, and the interface development area ratio (Sdr) is 0.35, confirming the significant damage of the microscopic structure. From Figure 3The 2D and 3D morphology images (c and 3d) show that after treatment, the arithmetic mean height (Sa) of the moldy film surface is 0.05 μm, the maximum height difference (Sz) is 1.60 μm, and the unfolded area ratio (Sdr) is 0. Data comparison shows that the arithmetic mean height, maximum height difference, and unfolded area ratio of the moldy film surface are all significantly reduced after treatment, indicating that the mold removal method of this invention restores the film surface to a smooth and flat state.

[0058] Test 4

[0059] During long-term storage, black and white photographic negatives are susceptible to mold growth on the back coating due to environmental factors. Mold erosion damages the originally smooth surface structure of the negative, creating an uneven microstructure. This change in morphology directly affects light propagation characteristics, leading to a significant increase in reflected light and a corresponding decrease in transmitted light during the printing process. Ultimately, this results in blurry images in the printed photographs. Testing revealed that the visible light reflectance of mold-affected black and white photographic negatives ranged from 9.5% to 12%. Figure 4 (Red line). After treatment using the method of Example 1 of this invention, the reflectance of the moldy black and white photographic negative under visible light is significantly reduced and can be stably controlled between 6.5% and 9%. Figure 4 (Blue line). Experimental data shows that the present invention can effectively improve the situation of increased diffuse reflection on the film surface caused by mold erosion, significantly reduce visible light reflectance, thereby effectively restoring the clear image of black and white photographic negatives and improving the imaging quality of printed photos.

[0060] Test 5

[0061] Chemical functional group analysis and molecular structure characterization were performed on the black and white photographic negatives of Example 1 before and after mold removal using mid-infrared-far-infrared spectroscopy. The results of the infrared spectral characterization analysis are as follows: Figure 5 As shown.

[0062] from Figure 5 It can be seen that in the infrared spectrum (black curve) of the unrestored moldy black and white photographic negative, at 1630 cm⁻¹... -1 1543cm -1 1228cm -1 The absorption peaks at 3287 cm⁻¹ correspond to amide bands I, II, and III in the gelatin, a component of the film; -1 and 2944cm -1 The absorption peak at this point is attributed to the amide A and amide B bands of gelatin, which are characteristic absorption peaks of proteins. In the infrared spectrum (red curve) of the black and white photographic negative after mold removal, the peak at 1739 cm⁻¹... -1 The absorption peak at 1220 cm⁻¹ corresponds to the characteristic peak of the ester carbonyl group and is the most prominent characteristic peak of cellulose triacetate.-1 The absorption peak at 1740 cm-1 corresponds to the ester group C-O stretching vibration, and forms a "doublet" with the carbonyl peak, which is a marker of high degree of substitution of esters, 1037 cm -1 The absorption peak at 1037 cm-1 is the stretching vibration of the C-O-C ether bond (β-glycosidic bond) in the sugar ring, and the peak intensity is high, including the skeleton and ester bond vibration, which is a common feature of cellulose compounds.

[0063] The above black and white photographic film before and after the removal of the mold spot of Example 1 was tested; the black and white photographic film before and after the removal of the plant protein hydrolase of Example 2 was tested according to the test method, and it was found that it also showed the same effect as the removal of the mold spot of Example 1, indicating that the plant protein hydrolase indicated that the animal protein hydrolase effectively removed the mold spot, and also destroyed the nutrient supply system required for the growth of mold, preventing the generation of mold spots. The removal method of the present application also reveals that the protein hydrolase selectively degrades the mold on the surface of the film and the gelatin layer rich in nutrients, exposing the film base layer. Through this treatment, the nutrient supply system required for the growth of mold is destroyed, making it difficult for subsequent mold to colonize and reproduce due to the lack of carbon and nitrogen sources and other nutrients provided by the gelatin matrix, thereby constructing a protective mechanism to inhibit the breeding of mold on the surface of the film base, achieving the effect of long-term mold prevention.

[0064] The above are several preferred embodiments of the preparation method of the present application, but they cannot be regarded as a limitation on the technical solutions protected by the present application. Any alternative solution obtained by ordinary technical personnel based on the technical ideas of the present application without creative labor shall fall within the protection scope of the present application.

Claims

1. A method for removing mold stains from a back coating layer of a moldy black-and-white photographic film, characterized by, The method comprises the following steps: S1, dust removal, cleaning and drying of the moldy black and white photographic film are performed to complete pretreatment; S2, ethyl cellulose solution is applied to the emulsion layer of the pretreated moldy black and white photographic film to form a natural film; S3, further applying protease solution to the back coating surface of the moldy black and white photographic film after step S2, and after 20-30 minutes of reaction, cleaning, drying are performed to complete the process.

2. The mold spot removal method for moldy black-and-white photographic film back coating according to claim 1, characterized by, In step S1, cotton soft wipes are used to remove dust; n-butanol is used for cleaning.

3. The mold spot removal method for moldy black and white photographic film back coating according to claim 1, characterized by, In step S2, the concentration of the ethyl cellulose solution is 5±0.5%.

4. The mold spot removal method for moldy black and white photographic film back coating according to claim 1, characterized by, In step S3, the concentration of the protease solution is 5±0.5%; the protease solution is animal protease solution or plant protease solution.

5. The mold spot removal method for moldy black and white photographic film back coating according to claim 1, characterized by, In step S3, the protease solution is first dropped on the absorbent paper; then the absorbent paper is attached to the back coating surface of the moldy black and white photographic film.

6. The mold spot removal method for moldy black and white photographic film back coating according to claim 1, characterized by, In step S3, n-butanol solution is used for cleaning.

7. Application of protease in removing mold spots on the back coating layer of moldy black and white photographic film.

8. Use according to claim 7, characterized in that, In the application, the protease solution is first dropped on the absorbent paper; then the absorbent paper is attached to the back coating surface of the moldy black and white photographic film.

9. Use according to claim 8, characterized in that, Before attaching the absorbent paper to the back coating surface of the moldy black and white photographic film, the moldy black and white photographic film needs to be treated as follows: Dust removal, cleaning and drying of the moldy black and white photographic film are performed; then ethyl cellulose solution is applied to the emulsion layer of the moldy black and white photographic film to form a natural film.

10. Use according to claim 9, characterized in that, The concentration of the protease solution is 5±0.5%; the protease solution is animal protease solution or plant protease solution; the concentration of the ethyl cellulose solution is 5±0.5%.

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