How to intercept ancient murals and how to protect them? Do you have any books to recommend?

Ancient murals are best preserved in situ. If the ancient murals are uncovered, as far as the current technical conditions are concerned, it will inevitably cause different degrees of damage to the ancient murals. However, ancient murals are widely distributed, and there are murals in many ancient tombs, but it is impossible to build a museum to protect cultural relics in the original site of each ancient tomb. Therefore, many ancient murals must be protected and excavated.

The protection of murals can only be used passively if other methods can't save it. Because the mural itself and its affiliated buildings are regarded as a whole, the overall protection is the most ideal.

Three forms of mural peeling: peeling off pigment layer; Uncover the pigment and the bottom layer; Uncover the murals on the battlefield floor.

Remove pigment layer

This process operation is that the hardness of the grounding electrode and the adhesion of the pigment layer are not enough for the pigment layer and the grounding electrode to be removed together, or the grounding electrode is too thin, or it is hoped to remove a lighter mural, or the surface of the mural is uneven, such as the vault mural, and the picture is uneven. Another point is that this method is the only way to expose the manuscript when there are traces left on the local staff layer, but it requires extremely skilled skills when removing it. After the picture is removed, it needs an extremely flat and even surface to be placed on a new plane support. Moreover, after the mural is removed by this method, the original unique surface state (adding arch surface, curved surface and so on) is removed. ) has been lost, so this method should only be applied when absolutely necessary.

Before deciding on this process operation, a simulation test must be done to determine whether this method is feasible. This test can be carried out in an inconspicuous area.

When the cloth is attached to the mural, the shrinkage glue after drying helps to peel off the pigment layer. Because the relative temperature of the atmosphere will affect the drying speed at that time, this method is usually carried out when the relative temperature of the atmosphere is the lowest (40%-60%) in a year, and it should never be removed in a frosty atmosphere. If necessary, you can use a small heater, such as an infrared lamp, to dry the wall. Of course, excessive drying should be avoided to avoid warping of pigments.

The main steps are: 1 dust removal; 2. Strengthen the picture; 3. sub-map; 4 brush the first layer of glue and stick gauze; 5 brush the second glue and stick the glass fiber cloth; 6 uncover

Advantages: wide application range and large peeling area; This method can also be used to uncover murals that are not in the same plane; This method can only be used to uncover the situation that there is no ground combat or the ground combat layer is very thin.

Disadvantages; Complex operation, high requirements for repair materials and large dosage; The use of glue in the repair will affect the pigment layer, which is very troublesome to repair.

First, gently sweep the whole mural surface with a soft brush, clean the surface, and pay attention to removing organic matter (hard shell, edge, empty drum, etc.). ) hindered the process operation. Then apply the first layer of glue directly on the mural with a brush, and the concentration of glue should not be too low to avoid free flow. Generally use polyvinyl alcohol or peach gum. If the mural itself is not strong enough, it can be reinforced with the first layer of glue, and then coated with the first layer of glue. After sizing, the cloth is usually pasted with gauze or burlap. The size of the cloth is several centimeters larger than the mural to be demolished. Don't glue the extra area, but fold it back at the edge to facilitate the next stage of operation. The rest should be closely attached to the surface of the mural and leveled gently. And pay attention to observe that there is no bubble between the mural and the sticker. After the first layer of glue is dry and the first layer of gauze is firmly adhered to the wall, you can apply the second layer of glue, which is more mobile than the first layer. When the amount of the first glue is thick, it is necessary to prevent the weaving and printing of the veneer cloth from remaining on the surface of the pigment layer, and at the same time, it will shrink when it dries. The second layer of cloth can be made of relatively strong cotton cloth or coarse linen. Before the veneer cloth dries and the rubber material hardens, start the paint stripping operation. The drying time is not only affected by the relative temperature of the atmosphere, but also by the humidity of the wall and the rubber used. In a dry environment, the drying time is about 1-2 days, but if the environment is quite humid, the drying time needs to be longer. The drying time of rubber compound with organic solvent is shorter, and that with water as solvent is longer. If necessary, it depends on manual heating and drying.

The first step of the paint uncovering operation is to cut the paint layer neatly along the edge of the decorative panel cloth, the cutting depth slightly exceeds the thickness of the paint, and then support it firmly and evenly from the wall at right angles. First, from a lower corner, monitor whether the veneer cloth really pulls the paint layer out of the earth. When the paint layer is rolled on the roller from bottom to top, it is only used for plane painting. If necessary, you must take it out with a sharp knife (such as a scalpel) and lay it flat on a soft horizontal surface with your back up. At this time, tools such as sharp knives and files can be used to remove the debris of the grounding electrode that can be removed from the back to make the back as clean and flat as possible. At this time, you can brush a layer of glue on the back to reinforce the back of the pigment layer. After this layer of glue dries, you can decide whether to copy the grounding electrode on the back, and then you can reinforce it with glue and glass cloth.

If the ground paste is copied first, its composition should be the same as that of the original paste, and water-soluble or water-emulsified resin such as vinyl acetate emulsion or polyvinyl alcohol should be added to increase the firmness of the ground paste. When the pole is almost dry, the cracks that can appear should be wiped dry with a trowel, that is, adhesive and glass cloth can be coated on it. The glue used can be epoxy resin. The advantage of epoxy resin is that it will not shrink when cured, so it will not cause stress to glass cloth. Some people use calcium acetate as an adhesive, and of course they can also use poly (butyl methacrylate). After brushing the first layer of glue, paste the first layer of glass cloth, then brush it on the glass cloth several times repeatedly with a brush to make the glass cloth stick flat and close to the ground. After it is completely dried, brush the second layer of glue and paste the second layer of glass cloth in the same way as the first layer. When the second layer of glass cloth and glue is completely solidified and dried firmly, turn the whole mural upside down and let the picture face up, and you can start to dismantle the veneer cloth. If the adhesive system used for pasting is water-soluble, the veneer cloth should be softened with hot water. If the glue system used is solvent, the veneer cloth should be softened with the same organic solvent. During operation, cotton can be dipped in solvent to smear or gently wipe on the veneer cloth, so that the veneer cloth on the whole mural picture can be slowly removed. The operation should be patient and meticulous. Only when the adhesive is soft enough can the veneer cloth be uncovered, otherwise it will damage the pigment layer. When the glue is completely softened, you can gently uncover the facing cloth.

The pigment layer is removed together with the grounding rod.

When the mural is not suitable for removing only the pigment layer and is not prepared to be removed together with some walls, the usual practice is to remove the pigment layer of the mural together with the attached grounding electrode. The precondition of using this process is that the grounding electrode is firmly attached to the pigment layer, otherwise it will cause serious damage when removing the pigment layer. It can't uncover the area as big as the pigment layer at one time, so the speed of process operation is generally slow.

The first step of the operation is to clean the mural surface, try not to leave unnecessary obstacles to the operation, and pay attention to check whether the pigment layer on the whole mural surface is firm and whether the pigment layer is firmly combined with the grounding electrode. If there is any dissatisfaction, it needs to be reinforced to ensure that the mural picture is dry before taking it down. The pasting order and materials used in murals are basically the same as those of only uncovering the pigment layer. Because this process operation does not want it to shrink when it condenses, and because the weight of the mural uncovered by this method is much larger than that of the previous method, it is required that the top of the second piece of linen should be at least 30 cm higher and firmly nailed to the wall. If there is a picture on the wall, it should be nailed to a solid horizontal wooden beam.

Cut along the previously drawn peeling line with a sharp scalpel. At the same time, a wooden board with the same size as the uncovered mural should be prepared as a support when the mural is stripped and carried away in the future. After the stripping line is cut, the board can be attached to it as support. Cushion such as felt can be filled between the wooden board and the mural, and the excess part around the plaster is turned over and folded on the edge of the wooden board and firmly nailed to the back of the wooden board. At this time, special attention should be paid to the safety of the top of the mural.

At this stage, the pole can be peeled off from the wall, and the long shovel can be used as a lever to peel off between the pole and the wall, and the operation can be carried out from bottom to top. When the mural is completely peeled off, let it gradually flatten to about 1 cm. If the material is solid, it can be thinner, leaving only a thin layer of ground crew. Of course, the personnel here are still relatively solid. When it is dry, it will be transported back to the warehouse for future reinforcement. As for the materials and technology used for reinforcement, please refer to the method of removing pigment layer.

Uncover murals without a stick

Taking Li Xian's tomb murals as an example, the use of framing method is illustrated. Because the murals in Li Xian's tomb have no solid pole layer, the wall soil is loose, the picture is full of cracks, and the wall is full of holes and cracks, it is difficult to completely dismantle the murals if only the wallboard is used in front of the murals and stripped behind them. So imagine if you can cover the mural with a frame. After weighing the pros and cons repeatedly, it was decided that the shelf was 8 cm thick. 1984 confirmed during the official construction from June to August that this thickness not only ensures that the mural blocks are not damaged, but also has a proper weight. In the design of shelves, the movable shelf technology is adopted.

The problem of moving the template is solved by using the pull rod. The size of the frame can be selected according to the size of the uncovered mural block. The biggest feature of this framework is its flexibility and easy application. You can first put the border on the four sides of the wall tile, tighten the nut, fix the pull rod, and then put the front wall panel. The operation is very convenient, safe and reliable, and there is no need to operate murals. After the mural is removed, the rear wallboard is also easy to install. Generally speaking, it is quite safe as long as violent vibration is prevented during transportation.

The process of uncovering murals

(1) The preparations before the mural is unveiled include: a cleaning the mural, b copying the mural, taking photos or videos with 2%, 5% and 10% polyvinyl butyral solution respectively, and 10% polyvinyl alcohol solution d washing the mural tomb with rainwater. After uncovering the tomb and the lid of the tomb, cover the temporary tent E to remove the danger above the mural.

(2) Marking: According to the specific situation and mural content, divide and mark the murals that need to be uncovered, which can be uncovered as a whole or in blocks. After marking, write down the split dimension drawing for splicing in future repairs.

(3) According to the size of the mural line, do a good job of framing. The cover plate must be flat, especially the cotton cloth next to the mural, so as not to affect the smoothness of the mural in the future.

(4) Divide the sideline, remove the soil along the sideline, use tools such as knives and shovels to remove the soil, expose the sideline of the mural to be uncovered, and the depth should exceed the thickness of the unexposed mural, leaving the sideline at the lower part of the mural, without removing the soil temporarily, so as to ensure the safety of the mural.

(5) Drying frescoes (drying) generally uses infrared lamps to dry.

(6) Repairing and filling holes in the picture are made into mortar with similar color to the picture by mixing polyvinyl acetate emulsion and appropriate colored powder, and then dried.

(7) enhance the picture. Brush the pre-prepared three kinds of polyvinyl butyral ethanol solutions with different concentrations from dilute to thick, and brush them again in a semi-dry state each time. After the last brush, continue baking and let them dry thoroughly.

(8) Paste: Brush the prepared 10% polyvinyl alcohol solution on the picture, paste a layer of gauze, and dry it again. After drying, remove the soil outside the lower edge of the mural to the required depth (more than 8 cm).

(9) Set the border. Carefully set the border on the mural and tighten the nut.

(10) Cushion wrapping paper and cotton Because the murals are uneven, all gaps need to be filled with wrapping paper, old cotton and sawdust to make the surfaces basically flush.

(1 1) The upper wall panel will rest on the upper frame. After drilling with an electric drill, install wood screws, tighten the screwdriver and add support.

(12) Saw off the soil on the back of the wall. Saw the soil from the back along the frame from top to bottom with a knife. When approaching the bottom below, you should be especially careful and correctly grasp the murals and put them on the ground, and at the same time release the support quickly.

Uncovering murals, we should also pay attention to the following aspects:

The material that constitutes the staff layer.

1April, 986, the mural painting of Li Xian's tomb was restored and reinforced. Because the mural is attached to the soil layer, which is the original underground soil layer, porous, cracked, loose and unstable, in order to ensure the safety of the mural, it is necessary to replace the loose soil layer with a new and stronger pole.

After the experiment, one to three layers of poles were made with the mixed system of polyvinyl acetate solution, hydrated lime paste, wool tendons, white cement and fine sand, and the total thickness was 1- 1.5 cm. After fully dry hardening, 3-4 layers are reinforced with E44 epoxy resin, 305 1 "polyamide resin 50 1" active diluent, ethylenediamine, acetone and glass fiber cloth. The total thickness of the repainted pilaster is 1.5-2 cm, which is stronger and lighter. In order to prevent cracking and reduce shrinkage of poles in emulsion-lime-white cement-fine sand-wool reinforcement system, this supplementary pole mud must be quite thick, just like dough.

Prevent the stick from getting stuck in the hole of the mural.

Because it is inevitable to damage the picture in the process of shoveling and scraping the soil, sometimes the mural picture will fall off and become empty when removing the soil layer. Therefore, it is necessary to solve the problem of preventing the newly made stick from sticking to the picture.

The methods of drying gypsum powder and coating paraffin liquid were used in the experiment. The results show that the anti-adhesion effect of paraffin liquid is better.

Underpinning design

In the past, when restoring murals, most of them used wooden strips to support a cross-shaped floor as a base, and murals were directly attached to the floor. We consider making a base in the form of an imaging frame and embedding murals in the frame. Its form is still a movable form, just like the frame for putting works of art, which can be taken down from the frame when necessary.

For the monograph on the protection technology of ancient murals, please refer to the Protection Technology of Library Murals (published by Science Press) and the Report on the Protection and Restoration Project of Potala Palace Murals in Tibet (published by Cultural Relics Press).