(1) turpentine has a weak effect on old oil paintings, but it has a strong effect on new color layers, especially after being heated with hot water.
(2) Refined gasoline and benzene (toluene and xylene). The solubility of resin is stronger than turpentine.
(3) Ethanol (anhydrous alcohol) and methanol (lignin). It is a powerful solvent for resin.
(4) acetone and chloroform. Can quickly dissolve resin and oil layer. Cleaning agents sold in art shops are generally mixed with several solvents, and strong solvents cannot be used alone. Modern oil paintings mostly use resin varnish, which can be washed off with turpentine. The older generation of oil painters in China mostly use oily varnish, which needs turpentine and anhydrous alcohol to mix. Acetone is only used as an additive when cleaning ancient works.
(5) hydrogen peroxide. There are many rare white pigments, which are lead salts. There is a trace of hydrogen sulfide in the air. Hydrogen sulfide will react with lead ions, and the production of solid lead sulfide close to black will darken oil paintings, while hydrogen peroxide can oxidize lead sulfide into white lead sulfate.
Wipe method: Dip a white absorbent cotton ball (available in pharmacies) in detergent, and do circular wiping from the corner of the screen. It is not easy to wipe all parts for too long to avoid damaging the color layer. Cotton balls should be replaced immediately after being dyed with yellow varnish. Most of the old varnish can be washed off in the first pass, and strong solvent can be added to the stubborn part in the second pass. Dirt marks and fly excrement stains caused by extrusion injury can be removed with a knife. Painting protection principle and basic repair process.
Identification before maintenance
First of all, make a detailed inspection of the work before restoration. The inspection process can be divided into four aspects:
First, textual research of the works.
Know the author and the year of creation, and know the relevant information and painting characteristics of the painter, such as materials, colors, brushstrokes, creative styles, creative ideas and aesthetics. This kind of investigation can help the restorer to establish a deeper understanding with the work, and then grasp the original creative face of the work more accurately during the restoration process.
Second, national comments.
First of all, it is necessary to determine whether the painting technique is oil painting or rubber painting, and record the size, theme, artist's signature, completion date, storage status of inner frame and outer frame of the work, and then make an in-depth analysis after recording these basic situations.
A. Base material: used to distinguish whether the base material is flax, jute, hemp, cotton cloth, mixed fiber, wood board or fiberboard: the fixing method is to use nailing needles or nailing guns; Whether the storage conditions are damaged, oxidized and corroded, damp and moldy, and invaded by microorganisms or insects; Whether it has been repaired by predecessors, the repair method and the adhesive used.
B. Substrate coating: Understand the color of the substrate coating to see if the substrate is separated, floated, cracked, peeled off or invaded by microorganisms.
C. Paint layer: an adhesive for analyzing pigments; Thickness and thickness of paint layer; Whether the hue is bright, gray or dark: whether the color technique used is transparent or opaque; whether the brush strokes are delicate or rough; Whether the paint layer cracks, whether it is partial or comprehensive, how deep the crack is and whether it begins to peel off; Whether there are blisters on the surface of the color layer. Comment and analyze the degree of these factors.
D. Protective layer: First, distinguish whether there is a protective layer, whether it is fully coated or partially coated, and the number and thickness of coating. Carefully distinguish whether the transparent color and the color of the Varne layer are diseased or destroyed by microorganisms.
Third, laboratory diagnosis
Ultraviolet radiation: ultraviolet radiation can penetrate the protective layer and paint layer. When this ultraviolet light shines on the surface of the work, it will present blue-purple refracted light. Using this refracted light, we can judge the chemical reaction of the coating and the pathological condition of the protective layer.
B. Infrared ray: Its radiation principle is the same as X-ray, but its radiation function is not as strong as X-ray, but its perspective range is far beyond ultraviolet ray, and it can reach the coating and sketch layer of the base material, so it can provide quite correct information for restorers.
Fourth, take photos and file them.
Before and after the restoration of a work of art, there is a completely different feeling. Therefore, it is necessary to take photos and file them before repair as a witness for future comparison. In addition, in the process of restoration, you often need the original photo of the work as an aid to master the color and composition of the whole work. The key points of taking pictures include the complete front, back, inside and outside frame of the work, and then take local close-ups with macro lens.
First, prepare a new canvas.
Select fine and uniform fine linen, and stretch the canvas on a frame 10-20cm larger than each side of the original canvas. When stretching the cloth, keep the straight line distance constant, so that stretching the canvas will not cause imbalance of power. Then spray the canvas with water, rub it by hand when it is dry, and then tighten it. Repeat this three or four times to avoid disharmony between the old and new canvases and increase adhesion.
Second, the preparation of old paintings
A. Removal and cleaning of the inner and outer frames: The removal of the inner and outer frames must not be arbitrarily forced, so as not to hurt the paint layer and substrate. Use a vacuum cleaner to gently absorb the dust on the surface, or use a brush to brush the capillary. When doing these jobs, you must be gentle and careful.
B, flattening the canvas: paste the painting on the wooden frame with acid-free kraft paper. Paste the edge picture to avoid peeling during flattening.
Phenomenon, you need to stick cotton paper on the picture, and then stick kraft paper around the picture covered with cotton paper. The framed old cloth will be naturally tightened and leveled by the tension of the four sides in the process of drying in the shade.
C, cleaning the back of the old painting: When the old painting is mounted on cotton paper, you can reverse the work and clean the back. Generally, old works are preserved for a long time, and a lot of dust, bacteria and eggs will be attached to the back surface, so they should be thoroughly cleaned up, otherwise the adhesion effect after transplantation will be affected.
First, clean up the picture
When preparing a clean solvent, we must first distinguish the strength of the solvent. Many solvents will seriously damage the materials used in the works after use, and sometimes even corrode the coating of the works, making the texture of the coating soft, such as acetic acid, ammonia water, amine butyrate and so on. Commonly used solvents are: white alcohol for painting, pure turpentine, alcohol, acetone, benzene, xylene and so on. Many solvents can be mixed into two or three kinds. Each solvent has its own characteristics and dissolution, which depends entirely on the pollution degree of the material and the tolerance of the work. But in any case, the most basic thing is that the restorer must first test the cleaning function of the solvent in a corner of the work to make sure there is no problem before using it, so as not to cause regrettable damage to the work. The cleaning process is to dip cotton in the prepared solvent, smear it on the surface of the work and gently wipe it. Gradually, it can be found that cotton turns dark yellow due to infection with Wannis layer or dust. Generally, it can be determined that cotton is clean until it is no longer contaminated with any stains, and at the same time, it must not harm the pigment. The success of cleaning depends entirely on personal experience and judgment on repair.
Second, fill in white pulp.
If the surface of the work is cracked, peeled off or damaged seriously, resulting in many holes, it should be filled with white paste to restore the flat surface. The materials used are water-based animal glue, water-insulated heating and gradually adding a little honey, phenol and hydrated lime. The heated white paste is applied to the hollow space and corresponding strokes are formed around it. The filled white paste is white.
Third, complementary colors
The work of complementary colors has caused controversy among many artists and scholars. Because the complementary color undoubtedly comes from the restorer, some people think that it will destroy the aesthetic value of the original painting. On the other hand, some people think that this can be called making up for the defects of damaged works. When deciding to make complementary colors, we must first analyze the color hierarchy to ensure the restoration effect. The material used for complementary color should be high-quality watercolor, which is convenient and risk-free. Because it can be washed with water at any time. After the background color is dried, it is easy to remove it with turpentine by applying Vannis (protective varnish) and then applying special oil paint. In principle, the complementary color should be lighter than the surrounding color, so as to distinguish it later. All the supplements can be easily removed in the future. After the above series of work, a worn-out work is basically repaired. As for the work of framing, it can be decided according to the work content and personal hobbies.
The long-term preservation of oil paintings should be the main task of collectors. It is necessary to find out the cause of the damage and eliminate it in order to ensure that the life of a work can be extended as much as possible. The protection of painting in major museums and art galleries in China is almost blank, and the protection of painting involves a variety of fields, which is worthy of in-depth study. This paper gives a general introduction to the protection of painting in order to attract the attention of cultural circles. Compared with other paintings, oil painting has its limitations in display. First of all, it is easy to reflect light. In addition, thick painting emphasizes the texture of the picture, because ups and downs are easy to accumulate dust. In order to achieve a better visual effect and protect the picture, there should be a downward tilt when hanging. When oil painting faces the front light, the effect is often poor. The front and upper light should be used, and the light source at the suspension should be as consistent as possible with the light source when painting. If the light source is on the left when painting, it should be consistent with this light source when hanging.
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