A durable coloring method for non-inheritable brick carvings

Abstract

This invention provides a durable coloring method for intangible cultural heritage brick carvings, belonging to the technical field of intangible cultural heritage brick carving decoration. It solves the technical problems of existing outdoor intangible cultural heritage brick carving coloring, such as easy fading, peeling, and flaking, as well as limited color variety and weak artistic expression. The method involves shallowly carving a 2mm closed groove with an inwardly inclined interlocking opening in the area to be decorated. After cleaning and drying, a layer of mineral powder is laid according to a formula, followed by the application of outdoor-specific epoxy resin containing UVA and HALS and curing. Finally, an outdoor brush-applied aliphatic polyurethane varnish is applied according to a formula, with optional sanding and finishing. This invention utilizes a composite process of mechanical interlocking grooves, mineral powder coloring, modified resin bonding, and polyurethane varnish protection. Combined with a quantitative formula, it achieves precise parameter control, resulting in a decorative layer with strong adhesion, excellent weather resistance, rich colors, and long-lasting colorfastness without damaging the original three-dimensional shape of the brick carving. The process is highly controllable, suitable for partial / overall decoration of various intangible cultural heritage brick carvings, significantly enhancing the artistic value and outdoor lifespan of the brick carvings.

Description

Technical Field

[0001] This invention belongs to the technical field of intangible cultural heritage brick carving decoration techniques, and more specifically, it relates to a durable coloring method for intangible cultural heritage brick carving. Background Technology

[0002] Intangible cultural heritage brick carving is an important treasure of traditional Chinese architecture and folk art. It is widely used in gate tower plaques, relief panels, architectural ornaments and other scenes. Color decoration is the core means to enhance its artistic expression and visual level. In particular, the color durability of outdoor brick carving directly affects its ornamental value and service life.

[0003] Currently, there are two main techniques for outdoor color decoration of intangible cultural heritage brick carvings, both of which have significant technical defects:

[0004] One issue is the direct application of modern chemical paints. However, chemical paints have weak adhesion to the micropores of bricks, making them prone to discoloration, peeling, and flaking under outdoor weather conditions such as wind, rain, and UV radiation, resulting in a short decorative effect.

[0005] Secondly, there is the traditional black coal particle pasting technique, which uses traditional adhesives such as glutinous rice glue to paste coal particles to achieve black decoration. This technique not only has a single color and lacks diverse color and material decorative effects, but also has poor adhesion between the coal particles and the brick body, making it easy to peel off and flake. This results in high maintenance frequency and cost. Furthermore, this technique cannot give key parts such as brick carvings, gate towers, and plaques sufficient three-dimensionality and prominence, resulting in a monotonous overall decorative effect and weak artistic expression.

[0006] Existing technologies, whether chemical paint coating or traditional coal particle bonding, have not solved the core problems of firm adhesion and outdoor durability of brick carving decorative layers. Nor have they achieved richer and more precise color decoration while maintaining the original three-dimensional shape of the brick carving, making it difficult to meet the needs of contemporary intangible cultural heritage brick carving protection and decorative upgrading. Therefore, developing a durable coloring method for intangible cultural heritage brick carvings that can achieve long-lasting and firm color adhesion, rich artistic expression, and without damaging the original shape of the brick carving has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a durable coloring method for intangible cultural heritage brick carvings. This method solves the technical problems of existing outdoor intangible cultural heritage brick carvings, which are prone to fading, peeling, and flaking when coated with modern chemical paints, and the traditional method of using coal particles to adhere to bricks, which results in limited color options, easy detachment, and weak artistic expression. Furthermore, neither of these methods can achieve long-lasting and firm color adhesion and rich decoration while maintaining the original three-dimensional shape of the brick carving.

[0008] A durable coloring method for intangible cultural heritage brick carving includes the following steps:

[0009] 1) Without damaging the original three-dimensional shape of the brick carving, a groove with a depth of 2mm is shallowly carved in the flat area of ​​the brick carving to be decorated. The groove has a clear closed boundary and the edge of the groove is set as an inwardly inclined lock.

[0010] 2) After cleaning and drying the groove obtained in step 1), lay a mineral powder layer within the plane enclosed by the groove. The thickness of the mineral powder layer should be sufficient to cover the base color of the brick surface. The target thickness H0 of the mineral powder layer is determined by the formula:

[0011] H0 is calculated as H0 = K × (S / 100) + 0.1, where K is the brick porosity correction coefficient, ranging from 0.02 to 0.08 mm, and S is the unit area of ​​the brick carving to be decorated, in cm².

[0012] 3) Drip outdoor-grade epoxy resin into the groove where the mineral powder layer was laid in step 2), so that the epoxy resin completely covers the mineral powder layer, and let it stand to cure; the outdoor-grade epoxy resin contains ultraviolet absorber (UVA) and light stabilizer (HALS).

[0013] 4) After the epoxy resin in step 3) has fully cured, coat its surface with a layer of outdoor brush-applied aliphatic polyurethane varnish (PU).

[0014] Preferably, the inward inclination angle of the lock-shaped groove in step 1) is 15°~45°, and the inward inclination surface of the groove sidewall is a smooth surface.

[0015] Preferably, the mineral powder mentioned in step 2) is rock color mineral powder, and the particle size of the mineral powder is 100 mesh to 800 mesh. Single-color mineral powder or a mixture of mineral powders with multiple particle sizes / colors can be selected and laid according to design requirements.

[0016] The brick porosity correction coefficient K is determined based on the actual porosity of the brick carving material. When the brick porosity is ≤10%, K is 0.02~0.04mm; when the brick porosity is 10%~20%, K is 0.04~0.06mm; and when the brick porosity is ≥20%, K is 0.06~0.08mm.

[0017] Preferably, when multi-colored mineral powders are mixed and laid, a layered laying method is adopted. The thickness of each color mineral powder layer is calculated by formula and distributed according to the design ratio. A gap of 0.1~0.3mm is reserved between each color mineral powder layer. When epoxy resin is dripped in, the resin fills the gap.

[0018] Preferably, the cleaning process in step 2) involves using a high-pressure air gun to blow away brick chips and dust from the groove, and then wiping the inner wall and bottom of the groove with anhydrous ethanol. The drying process involves natural drying at room temperature of 25~30℃ for 4~6 hours, or hot air drying with a hot air temperature ≤40℃ and a drying time of 1~2 hours.

[0019] Mineral powder layer can only be laid when the moisture content in the groove of the brick carving is ≤0.5% after drying.

[0020] Preferably, the solid content of the outdoor-specific epoxy resin in step 3) is above 90%, and the epoxy resin dripping thickness H1 satisfies H1=H0+0.2~0.5mm, where H0 is the calculated target thickness of the mineral powder layer. The curing process is divided into initial curing and complete curing. The initial curing condition is standing at 25℃ for 12~24h, and the complete curing condition is standing at 25℃ for 48~72h.

[0021] Preferably, the ultraviolet absorber (UVA) mentioned in step 3) is a benzophenone-based or benzotriazole-based ultraviolet absorber, and its addition amount in the epoxy resin is 0.5% to 2% of the total mass of the epoxy resin;

[0022] The light stabilizer (HALS) is a hindered amine light stabilizer, and its addition amount in the epoxy resin is 0.3% to 1.5% of the total mass of the epoxy resin;

[0023] The total amount of UV absorber and light stabilizer added, M, must satisfy M≤3% (as a percentage of the total mass of epoxy resin).

[0024] Preferably, the aliphatic polyurethane varnish (PU) in step 4) has a solid content of 60%~80%, and the coating thickness H2 is calculated by the formula H2=0.05×√H0. The coating thickness ranges from 0.1 to 0.3 mm. It is applied evenly with a brush in the forward direction and cured in a ventilated environment at room temperature for ≥24 hours.

[0025] Preferably, after applying aliphatic polyurethane varnish (PU) in step 4), the process also includes a sanding treatment after the varnish has cured. Wet sanding is performed using wet sandpaper with a grit of 2000 or higher. After sanding, the surface is wiped with clean water and dried so that the flatness of the brick carving decorative surface is ≤0.05mm. The remaining thickness of the varnish after sanding is not less than 80% of the calculated H2.

[0026] Preferably, the method is applicable to the partial or overall color decoration of intangible cultural heritage brick carving gate plaques, brick carving relief decorative panels, and brick carving ornaments, and the non-decorative areas of the brick carving are covered and protected with a protective film during the entire coloring process.

[0027] The protective film is applied to an area that extends 1-2 cm beyond the edge of the non-decorative area to prevent contamination of the original brick carving during construction.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] A 2mm closed groove is shallowly carved only in the flat area of ​​the brick carving to be decorated, without damaging the original three-dimensional shape of the brick carving. The interlocking structure of the groove enables the decorative layer to be mechanically fitted into the brick body. Combined with quantitative formulas to control the thickness of each layer, the color can be added precisely, solving the problems of traditional coloring without fixed boundaries and easy contamination of the original shape of the brick carving.

[0030] Using mineral powder as the coloring base material, the mineral components do not change color in the natural environment, solving the problem of color fading at its source. Outdoor-specific epoxy resin with added UVA and HALS fully combines with the microporous structure of the brick material, while forming a strong composite layer with the mineral powder. The secondary protection of aliphatic polyurethane varnish further enhances the weather resistance, water resistance, and peel resistance of the decorative layer. It shows no peeling after 12 months of outdoor placement, with a color difference ΔE ≤ 1.4 and a cross-cut adhesion rating of 0, far superior to traditional chemical paints and ancient coal particle bonding techniques.

[0031] Breaking away from the limitations of traditional methods that can only achieve black decoration, single-color or multi-color mixed mineral powders can be selected according to design needs, supporting layered laying to achieve color gradient effects. The granular texture of mineral powder combined with the transparent texture of resin gives brick carvings, gate towers, and other parts a stronger sense of three-dimensionality and prominence. The colors are rich and the layers are distinct, greatly enhancing the artistic value and visual impact of intangible cultural heritage brick carvings.

[0032] The original formula for quantifying the thickness of the mineral powder layer and varnish layer allows for precise adjustment of process parameters based on the porosity of the brick material and the area of ​​the decorative region, adapting to intangible cultural heritage brick carving substrates with different porosities. The process steps are clear and the operation is simple, enabling partial or overall decoration of various intangible cultural heritage brick carvings (doorway plaques, relief panels, ornaments, etc.). Moreover, the construction process does not require complex equipment, making it suitable for large-scale and standardized construction, reducing construction difficulty and human error.

[0033] The composite decorative layer formed by this invention is firmly integrated with the brick body, and there are no problems such as peeling, flaking, or fading during outdoor use. It does not require frequent maintenance and repair, which greatly reduces subsequent maintenance costs. After being aged for 1000 hours under xenon lamps to simulate 2 years of outdoor environment, the decorative layer still maintains good integrity and color stability, which significantly extends the service life of outdoor color decoration of intangible cultural heritage brick carvings.

[0034] The process uses natural rock color mineral powder and environmentally friendly modified epoxy resin and polyurethane varnish, which are free of harmful volatile substances and meet the requirements of green construction. The process does not damage the brick carving itself, taking into account both the decorative upgrading of intangible cultural heritage brick carving and the protection of cultural relics, making it suitable for the inheritance and innovative application of intangible cultural heritage brick carving. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the present invention. Detailed Implementation

[0036] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0037] This invention discloses a durable coloring method for intangible cultural heritage brick carvings, aiming to solve the technical problems of easy fading, peeling, and flaking of existing outdoor coloring methods for intangible cultural heritage brick carvings, as well as the lack of color variety and weak artistic expression. This method involves shallowly carving interlocking grooves on the surface of the brick carving, combined with the composite adhesion of mineral powder and modified epoxy resin, and then layering an aliphatic polyurethane varnish for protection. This achieves durable and rich decorative coloring of the brick carving without damaging its original three-dimensional shape. The technical solution of this invention is described in detail below with specific embodiments, comparative examples, and precise experimental data. The scope of protection of this invention is not limited to the following embodiments; all equivalent modifications made based on the concept of this invention are included within the scope of protection of this invention.

[0038] The quantitative formula involved in this invention is the core of precise control of process parameters. All parameters are in mm. The formula and parameter definitions are as follows:

[0039] Formula for target thickness of mineral powder layer: H0=K×(S / 100)+0.1;

[0040] H0: Target thickness of mineral powder layer, which is the optimal thickness to cover the base color of the brick surface and adapt to the pores of the brick material;

[0041] K: Correction coefficient for brick porosity, ranging from 0.02 to 0.08 mm, adapted to the actual porosity of the brick carving (porosity ≤ 10%, K = 0.02 to 0.04; 10% < porosity < 20%, K = 0.04 to 0.06; porosity ≥ 20%, K = 0.06 to 0.08).

[0042] S: Unit area of ​​the brick carving to be decorated, in cm2.

[0043] Formula for aliphatic polyurethane varnish coating thickness: H2 = 0.05 × H0

[0044] H2: Optimal coating thickness of polyurethane varnish, with a range of 0.1~0.3mm, balancing protection and surface smoothness;

[0045] H0: The target thickness of the mineral powder layer calculated by the above formula.

[0046] The epoxy resin dripping thickness is H1 = H0 + 0.2~0.5mm, ensuring that the epoxy resin completely coats the mineral powder layer and fully combines with the micropores of the brick material.

[0047] Preparation of test substrates and reagents:

[0048] (a) Test substrate:

[0049] Three sets of intangible cultural heritage brick carving samples (gateway plaque design, size 30cm×20cm×5cm) from the same batch were selected and labeled as Sample 1, Sample 2, and Sample 3, respectively. The basic parameters of the brick material are as follows:

[0050] Sample number Brick porosity Area S to be decorated Porosity correction factor K Calculate the thickness H0 of the mineral powder layer Calculate the varnish coating thickness H2 Epoxy resin droplet thickness H1 Sample 1 8%（≤10%） <![CDATA[200cm 2 ]]> 0.03mm 0.03×(200 / 100)+0.1=0.16mm ≈0.10mm 0.16 + 0.3 = 0.46 mm Sample 2 15%（10%~20%） <![CDATA[200cm 2 ]]> 0.05mm 0.05×(200 / 100)+0.1=0.20mm ≈0.11mm 0.20 + 0.3 = 0.50 mm Sample 3 22%（≥20%） <![CDATA[200cm 2 ]]> 0.07mm 0.07×(200 / 100)+0.1=0.24mm ≈0.12mm 0.24 + 0.3 = 0.54 mm

[0051] (II) Test reagents and tools:

[0052] Mineral powder: Rock coloring mineral powder (red, black, and gold, particle size 100~800 mesh, single color / mixed use);

[0053] Epoxy resin: Outdoor-grade transparent epoxy resin, 95% solids content, with added benzophenone-based UV absorber (UVA, 1.0%) + hindered amine light stabilizer (HALS, 0.8%), total addition ≤3% 1.8%;

[0054] Varnish: Outdoor brushable aliphatic polyurethane varnish (PU), solids content 70%;

[0055] Tools: Miniature engraving machine (for shallow grooves), high-pressure air gun, anhydrous ethanol, brush (200 mesh), hot air dryer (≤40℃), protective film (to cover non-decorative areas).

[0056] Specific embodiments (samples 1-3 all adopted the method of the present invention)

[0057] Taking sample 1 as an example, the specific steps of the durable coloring method for intangible cultural heritage brick carving of the present invention are described in detail. Samples 2 and 3 only have the thickness of each layer adjusted according to the above parameters, and the remaining process steps are completely the same:

[0058] Step 1: Shallowly carve a lock-shaped groove:

[0059] Without damaging the original three-dimensional shape of the brick-carved gate plaque, a miniature carving machine is used to shallowly carve a 2mm deep closed groove in the area to be decorated, ensuring clear groove boundaries without burrs. The groove edges are machined into a 30° inward-sloping interlocking shape, and the inward-sloping surface of the interlocking is polished to a smooth surface, increasing the mechanical bonding strength between the epoxy resin and the brick and preventing edge lifting. Non-decorative areas are fully covered with a protective film, with the edge of the protective film extending 1.5cm beyond the non-decorative area to avoid construction contamination.

[0060] Step 2: Groove base treatment:

[0061] Cleaning: First, use a high-pressure air gun to blow away brick chips and dust in the groove, then use a lint-free cloth soaked in anhydrous ethanol to repeatedly wipe the inner wall and bottom of the groove to remove oil and dust.

[0062] Drying: Place the brick carving in a ventilated environment at 28℃ and let it dry naturally for 5 hours. The moisture content in the groove is tested and found to be 0.3% (≤0.5%), which meets the requirements for mineral powder paving.

[0063] Step 3: Laying the mineral powder layer:

[0064] Select red and gold mixed mineral powder (600 mesh red powder, 800 mesh gold powder, mass ratio 3:1), and use a 200 mesh brush to evenly spread the mineral powder in the grooved plane. The spreading thickness is precisely controlled to 0.16mm (calculate H0) to ensure complete coverage of the brick surface base color without any exposed base or accumulation.

[0065] Step 4: Add epoxy resin and allow it to cure.

[0066] Slowly drip modified outdoor-grade epoxy resin into the groove containing the mineral powder layer, controlling the drip thickness to 0.46 mm (calculate H1), ensuring that the epoxy resin completely coats the mineral powder layer and wets the micropores of the groove wall; after dripping, allow it to stand and cure, initially curing at 25°C for 20 hours and fully curing for 60 hours. During the curing process, keep the environment dust-free and vibration-free to allow the epoxy resin to fully bond with the mineral powder and brick.

[0067] Step 5: Apply aliphatic polyurethane varnish:

[0068] After the epoxy resin is fully cured, use a brush to evenly apply an outdoor brush-applied aliphatic polyurethane varnish in the direction of curing. The coating thickness should be precisely controlled to 0.10mm (calculate H2), with no drips or brush marks. After brushing, place the varnish in a ventilated environment at room temperature for 24 hours to cure and complete the varnish protection.

[0069] Step 6: Post-processing and finishing:

[0070] After the varnish has fully cured, wet sand the decorative surface with 2000-grit wet sandpaper, using gentle sanding force to avoid sanding through the varnish layer; after sanding, wipe the surface with clean water, and after natural drying, check that the flatness of the decorative surface is 0.03mm (≤0.05mm), and the remaining thickness of the varnish is 0.09mm (≥80% of the calculated H2), which meets the process requirements.

[0071] Samples 2 and 3 were constructed according to the above steps, except that the thickness of the mineral powder layer was controlled to be 0.20 mm and 0.24 mm respectively, the thickness of the epoxy resin dripping was 0.50 mm and 0.54 mm respectively, and the thickness of the varnish coating was 0.11 mm and 0.12 mm respectively. All other parameters were the same as those of sample 1, and all samples were successfully colored.

[0072] Scale settings:

[0073] To verify the technical superiority of the method of the present invention, three comparative examples were set up, all using the same brick carving samples as the examples (same batch of blue bricks, size 30cm×20cm×5cm, porosity 8%), only the coloring process was changed, and the other test conditions were the same as those in the examples. The comparative examples were designed as follows:

[0074] Comparative numbering Coloring process Core process parameters Comparative Example 1 Traditional chemical paint coating Commercially available outdoor acrylic paint is used, applied directly to the surface of the brick carving to a thickness of 0.5mm, without grooves or mineral powder treatment. Comparative Example 2 Traditional coal particle pasting Coal particles are bonded using traditional glutinous rice glue; the material is black only, without resin or varnish protection, and the coal particles are 0.2mm thick. Comparative Example 3 Simplified method of the present invention A shallow 2mm groove (without a locking mechanism) is carved, and 0.16mm of mineral powder is laid. Only ordinary epoxy resin (without UVA / HALS) is dripped in, and no varnish is applied.

[0075] Performance testing and results analysis:

[0076] The brick carving samples from Examples 1-3 and Comparative Examples 1-3 were placed in an outdoor natural environment for a 12-month weathering test, while an accelerated aging test was conducted in the laboratory (1000 hours of xenon lamp aging, simulating 2 years of outdoor environment). The test indicators included color stability, adhesion, peeling resistance, and water resistance. The test standards and results are as follows:

[0077] (a) Testing standards:

[0078] Color stability: The color difference ΔE (color difference) of the sample surface was measured using a colorimeter. ΔE ≤ 2 is excellent, 2 < ΔE ≤ 5 is good, and ΔE > 5 is poor.

[0079] Adhesion: Tested using the cross-cut test, with grade 0 being the best (no peeling), and grades 1 through 5 decreasing sequentially;

[0080] Peel resistance: After 12 months of outdoor placement, visually inspect whether the decorative layer peels or flakes off, and rate it as no peeling, slight peeling (≤5%), or severe peeling (>5%).

[0081] Water resistance: Immerse the sample in room temperature water for 72 hours, remove and dry it, and observe whether the decorative layer bulges or peels off. If there are no abnormalities, it is qualified.

[0082] (II) Test Results:

[0083] Group Outdoor 12 months ΔE Cross-cut adhesion rating 12-month outdoor peel resistance 72h water resistance Xenon lamp aging 1000hΔE Example 1 1.2 Level 0 No peeling qualified 1.8 Example 2 1.3 Level 0 No peeling qualified 1.9 Example 3 1.4 Level 0 No peeling qualified 2.0 Comparative Example 1 6.8 Level 3 Severe peeling (35%) Unacceptable (bulging) 9.5 Comparative Example 2 - (Black only) Level 4 Severe peeling (42%) Unqualified (detached) - Comparative Example 3 3.5 Level 1 Slight peeling (4%) qualified 5.2

[0084] (III) Results Analysis:

[0085] The performance of Examples 1-3 is far superior to that of the comparative examples, indicating that the composite process system of the groove lock structure + mineral powder + modified epoxy resin + polyurethane varnish of the present invention can achieve high adhesion and high weather resistance of the brick carving decorative layer, and solve the problems of fading and peeling of traditional processes.

[0086] Comparative Example 1 (Chemical Paint): Directly applied chemical paint has weak adhesion to the micropores of brick, is prone to aging and fading outdoors, and has poor water resistance, resulting in blistering and peeling, which verifies the inherent defects of traditional chemical paint.

[0087] Comparative Example 2 (Traditional Coal Particles): It is only glued with glutinous rice glue, without mechanical bonding and protective layer, resulting in extremely poor adhesion, easy peeling, and limited color and artistic expression.

[0088] Comparative Example 3 (Simplified version of the present invention): The absence of a locking groove leads to a decrease in the interlocking force of the epoxy resin. Ordinary epoxy resin has no UV-resistant components and no clear varnish protection. Although its performance is better than the traditional process, its color stability and adhesion are still significantly lower than the complete process of the present invention. This verifies the necessity of the three major technical features of the present invention: locking structure, modified epoxy resin, and clear varnish protection.

[0089] The performance of Examples 1-3 is slightly different but excellent. Due to the different porosity of the bricks, the thickness of each layer is quantitatively adjusted, which proves that the original formula of this invention can be adapted to bricks with different porosities. The process is highly controllable and applicable to various intangible cultural heritage brick carvings.

[0090] Process compatibility description:

[0091] The durable coloring method for intangible cultural heritage brick carvings of the present invention is not only applicable to the above-mentioned gate tower plaques, but also suitable for partial or overall decoration of various intangible cultural heritage brick carvings such as brick carving relief panels and brick carving ornaments:

[0092] For small-area decorations (such as brick carvings, S≤50cm2): calculate H0≤0.14mm according to the formula, H2≤0.09mm for varnish, and take 0.1mm (minimum value) to ensure a delicate decorative layer;

[0093] For large-area decoration (such as relief panels, S≥500cm2): calculate H0≤0.5mm according to the formula, epoxy resin H1≤1.0mm, and drip epoxy resin in layers (2 times) to avoid air bubbles generated by single dripping.

[0094] Multi-color gradient decoration: mineral powder is laid in layers, and the thickness of each color layer is distributed according to the design ratio according to the formula H0. A 0.2mm gap is reserved between the layers. When epoxy resin is dripped in, the gap is filled to achieve a natural color gradient and enhance the artistic expression.

[0095] Key process considerations:

[0096] Groove processing: The depth is strictly controlled to 2mm, and the inward inclination angle of the lock is 15°~45° (30° is optimal). If the angle is too small, the fitting force will be insufficient, and if the angle is too large, it will easily lead to the accumulation of mineral powder.

[0097] Drying process: The moisture content of the groove must be ≤0.5%, otherwise bubbles will be generated during the curing of epoxy resin, causing the decorative layer to peel.

[0098] Epoxy resin addition: The total addition of UVA and HALS should be ≤3%. Excessive addition will reduce the transparency and curing effect of the epoxy resin.

[0099] Varnish coating: A brush-applied aliphatic polyurethane varnish must be used. Spray-applied varnish is prone to uneven thickness and has weak adhesion to epoxy resin.

[0100] Sanding treatment: Use only wet sandpaper with a grit of 2000 or higher to avoid dry sanding which will cause dust to embed into the decorative layer. After sanding, the remaining thickness of the clear varnish should be ≥80%H2 to ensure the protective effect.

[0101] This invention achieves precise control of process parameters through quantitative formulas. Combining a four-layer technical system of mechanical inlay, mineral coloring, resin bonding, and varnish protection, it enriches the colors and enhances the durability of the decoration without damaging the original three-dimensional shape of the intangible cultural heritage brick carving. It solves the core pain points of existing technologies, and the process is simple to operate and highly controllable. It is suitable for large-scale and standardized coloring construction of intangible cultural heritage brick carving, significantly improving the artistic value and outdoor service life of intangible cultural heritage brick carving.

[0102] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A durable coloring method for intangible cultural heritage brick carving, characterized in that, Includes the following steps: 1) Without damaging the original three-dimensional shape of the brick carving, shallowly carve a groove with a depth of 2mm into the flat area of ​​the brick carving to be decorated. The groove has a clear closed boundary, and the edge of the groove is set as an inwardly inclined lock. 2) After cleaning and drying the groove obtained in step 1), lay a mineral powder layer within the plane enclosed by the groove. The thickness of the mineral powder layer should be sufficient to cover the base color of the brick surface. The target thickness H0 of the mineral powder layer is determined by the formula: H0 is calculated as K×(S / 100)+0.1, where K is the brick porosity correction coefficient and S is the unit area of ​​the brick carving to be decorated. 3) Drip outdoor-grade epoxy resin into the groove where the mineral powder layer was laid in step 2), so that the epoxy resin completely covers the mineral powder layer, and let it stand to cure. Outdoor-grade epoxy resin contains UV absorbers and light stabilizers; 4) After the epoxy resin in step 3) has fully cured, coat its surface with a layer of outdoor brush-applied aliphatic polyurethane varnish.

2. The method for durable coloring of intangible cultural heritage brick carvings according to claim 1, characterized in that, In step 1), the inward inclination angle of the lock-shaped groove is 15°~45°, and the inward inclination surface of the groove sidewall is a smooth surface.

3. The method for durable coloring of intangible cultural heritage brick carvings according to claim 1, characterized in that, The mineral powder mentioned in step 2) is rock color mineral powder. The particle size of the mineral powder is 100 mesh to 800 mesh. Single-color mineral powder or a mixture of mineral powders with multiple particle sizes / colors can be selected and laid according to design requirements. The correction coefficient K for brick porosity is determined based on the actual porosity of the brick carving material. When the brick porosity is ≤10%, K is taken as 0.02~0.04mm; when the brick porosity is 10%~20%, K is taken as 0.04~0.06mm; and when the brick porosity is ≥20%, K is taken as 0.06~0.08mm.

4. The durable coloring method for intangible cultural heritage brick carvings according to claim 3, characterized in that, When multi-colored mineral powders are mixed and laid, a layered laying method is adopted. The thickness of each color mineral powder layer is calculated by formula and distributed according to the design ratio. A gap of 0.1~0.3mm is reserved between each color mineral powder layer. When epoxy resin is dripped in, the resin fills the gap.

5. The durable coloring method for intangible cultural heritage brick carvings according to claim 1, characterized in that, The cleaning process described in step 2) involves using a high-pressure air gun to blow away brick chips and dust from the groove, then wiping the inner wall and bottom of the groove with anhydrous ethanol. The drying process involves natural drying at room temperature (25-30℃) for 4-6 hours, or hot air drying at a temperature ≤40℃ for 1-2 hours. Mineral powder layer can only be laid when the moisture content in the groove of the brick carving is ≤0.5% after drying.

6. The method for durable coloring of intangible cultural heritage brick carvings according to claim 1, characterized in that, The outdoor-specific epoxy resin mentioned in step 3) has a solid content of over 90%, and the epoxy resin dripping thickness H1 satisfies H1=H0+0.2~0.5mm, where H0 is the calculated target thickness of the mineral powder layer. The curing process is divided into initial curing and complete curing. The initial curing condition is to stand at 25℃ for 12~24h, and the complete curing condition is to stand at 25℃ for 48~72h.

7. The method for durable coloring of intangible cultural heritage brick carvings according to claim 1, characterized in that, The ultraviolet absorber mentioned in step 3) is a benzophenone-based or benzotriazole-based ultraviolet absorber, and its addition amount in the epoxy resin is 0.5% to 2% of the total mass of the epoxy resin; The light stabilizer is a hindered amine light stabilizer, and its addition amount in the epoxy resin is 0.3% to 1.5% of the total mass of the epoxy resin; The total amount M of UV absorber and light stabilizer added satisfies M≤3%.

8. The durable coloring method for intangible cultural heritage brick carving according to claim 1, characterized in that, The aliphatic polyurethane varnish mentioned in step 4) has a solid content of 60%~80%. The coating thickness H2 is calculated by the formula H2=0.05×√H0. The coating thickness range is 0.1~0.3mm. It is applied evenly with a brush in the forward direction. After application, it is cured in a ventilated environment at room temperature for ≥24h.

9. The durable coloring method for intangible cultural heritage brick carving according to claim 1, characterized in that, Step 4) After applying the aliphatic polyurethane varnish, the process also includes sanding after the varnish has cured. Use wet sandpaper with a grit of 2000 or higher for wet sanding. After sanding, wipe the surface with clean water and dry it so that the flatness of the brick carving decorative surface is ≤0.05mm. The remaining thickness of the varnish after sanding is not less than 80% of the calculated H2.

10. The method for durable coloring of intangible cultural heritage brick carvings according to any one of claims 1 to 9, characterized in that, The method is applicable to partial or overall color decoration of intangible cultural heritage brick carving gate plaques, brick carving relief decorative panels, and brick carving ornaments. During the entire coloring process, the non-decorative areas of the brick carving are covered and protected with a protective film. The protective film is applied to an area that extends 1-2 cm beyond the edge of the non-decorative area to prevent contamination of the original brick carving during construction.

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