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Paper repair and reinforcement methods

Repair and reinforcement are important links in the repair work, and are also components of effective measures to protect fragile paper and extend its life. Restoration technicians have not only accumulated rich experience in the restoration of ancient books, archives, calligraphy and paintings for a long time, but also made remarkable achievements in protecting ancient cultural heritage.

In recent years, monographs such as "Chinese Ancient Book Binding and Repair Technology" have been published one after another, making a systematic summary of this ancient traditional technology in our country. Many reinforcement methods are very valuable experience, and they are very useful for cultural relics. The development of restoration techniques will play a useful role in promoting it.

1. Repair--Pulp Repair Method

Traditional paper repair methods have been described in detail in the above-mentioned books, and we can use them flexibly in actual work. Generally speaking, with these methods, some common problems can be solved. However, researchers are not satisfied with the status quo and are still using new methods to repair. For example, some people use cellulose solution repair method. This method is to lay the paper that needs to be repaired flatly on the Kudzu board, and then inject a pre-prepared suspended cellulose (pulp, cotton fiber, resin) solution into the damaged or cavity-filled areas. When the solution penetrates downwards, the cellulose in the solution blocks the holes, fills them with defects, and repairs the paper.

Using pulp as a repair material for damaged parts of paper has been widely used. Its application methods include manual repair and mechanical repair, with mechanical repair being the main one. Mechanical repair is done with a pulp repair machine. Now we will introduce the structure and working principle of the pulp repair machine.

(1) Structure of the pulp repairing machine

The paper repairing machine consists of three parts: the upper half, the lower half and the control system. The door of the upper part can be opened. , the main part for repairing documents, the lower part has a water tank, a water pump and several jars for storing disinfection or sterilization drugs. With the assistance of an auxiliary vehicle, the medicine tank can fumigate and sterilize the repaired original parts. But this treatment can only be done in small quantities. The water tank supplies the necessary repair water with the help of a water pump, and the water is pumped back into the tank at the end of the repair. The control part has operation diagrams to provide operators with operation methods.

(2) Principles and steps of paper repair

1. First, measure the thickness of the repair part (paper), calculate the required amount of pulp, and put the slurry into the mixer Mix with water.

2. Put the paper document into water to clean, and at the same time lay the document flat on the protective paper. During the entire repair process, there must be a layer of protective paper to support the damaged document. The protective paper not only protects the original, but also plays a filtering role in the next step (the protective paper is a synthetic polyester fiber with excellent breathability). After the document is prepared, with the help of a trolley, it is placed flat on the metal mesh of the pulp repair machine, and then a thicker metal mesh is pressed on the document to help compress the document.

3. Press the electric button to fill the repair machine with water, and pour the mixed pulp into the machine and mix it with the water. (There are two ways to put pulp: one is to fill it with water first and then put the pulp, or you can put water and pulp at the same time). Then move the metal mesh above so that there is a certain gap between the metal mesh and the file.

4. Start the water pump and make the water flow to the damaged area under a certain vacuum pressure. Under the filtering effect of the protective paper, the paper fibers are blocked by the protective paper and deposited on the damaged area of ??the document and the document is bonded.

5. After the water is drained, take it out together with the protective paper, sandwich a few layers of absorbent paper on top and bottom, press it flat and shape, and wait until it is dry.

(3) Repaired pulp

Commonly used ones include flax, cotton and alkaline wood pulp. The flax fiber content is 85%, and the fastness is very good; the cotton fiber content is 90%, although the strength is not as good as flax, but the velvety is good; flax and cotton match, the paper has the highest quality, plus alkaline wood pulp, with these three The raw materials can be formulated into various slurries, and slurries of various colors can also be prepared according to actual conditions.

The fiber length of paper repair should be kept at about 30~35 degrees. If the fiber is too long, it will easily form lumps during mixing, but if the fiber is too short, it will not stick to the document easily, so it is important to control the length of the fiber.

In mechanical repair, the more serious the damage to the original, the faster the repair speed. The pulp area of ??the repair layer should be 5 to 10 mm larger than the original to achieve the purpose of protecting the original.

(4) Functions and limitations of the pulp repair method

The repairing principle of the repairing machine is basically the same as that of handmade papermaking. Handmade papermaking involves pulling fibers out of the water. The repair machine leaves the fibers behind. Therefore, the repair machine can not only repair damaged documents, but also make paper with various types of fibers as needed to meet the special needs of manual repair.

Paper pulp repair is not perfect. It is just a method to help manual repair. In general, the effect is good, but in some cases it is not. When the damage to the document is similar to that of tearing by hand, a certain amount of fiber is exposed in the damaged area, and the repair layer is well bonded and difficult to detach. And when the damage to the document is caused by a knife wound, if the damage is neat and no fibers are exposed, the bonding after repair will be poor and it will be easy to detach.

To solve the problem of poor bonding, the first is to use manual methods to pick out the damaged fibers; the second is to apply adhesive to the damaged areas, but applying adhesive will make the paper hard and deformed. Therefore, the first method is often better than the second method.

The principles of the manual pulp repair method and the pulp mechanical repair method are basically the same. The mechanical repair method is only an aid to manual repair, but it mainly relies on hands. Without hands, the machine will not work. stand up. But manual repair is very expensive and slow. In order to increase the speed, mechanical repair methods must be used to help repair.

2. Reinforcement methods

Reinforcement methods: coating and impregnating paper with a certain resin solution, or mounting and hot-pressing with paper, resin film, or wire mesh. Method to increase the strength of paper. The various methods are described as follows:

1. Mounting method:

Laying is my traditional technique and an effective reinforcement method. Generally, it can be divided into single-sided mounting and double-sided mounting. Single-sided mounting means mounting on the back with text. Double-sided mounting is suitable for paper with text on both sides. The supporting and mounting techniques are basically the same, the only difference is that the supporting paper requirements are different.

The paper used for double-sided mounting must be highly transparent and will not affect the reading of the text after reinforcement. For single-sided mounting, as long as the paper is of high quality. However, commonly used supporting papers are specially produced, such as Lianban, Lianshi, Chuanlian, etc.

Papering is a widely used method at present. The operation method is: cover the paper to be mounted with a wet towel, or spray it with clean water to moisten it and make it stretch and smooth. Apply slurry, cover it with support paper, and smooth it with a paste broom. When brushing the support paper, hold the other end of the paper with your left hand, gently lift the support paper and paper pages from time to time, and coordinate with the movements of your right hand. Do not brush too tightly or too loosely to avoid brushing. Remove the wrinkles and wait until everything is brushed, then turn it over and place it on a piece of dry paper, and brush it with a paste broom to make it adhere firmly.

Mounting is divided into wet and dry support. The operation method is basically the same. The main difference is that dry holding is to brush the paste on the supporting paper, while wet holding is to brush the paste on the document. The use should be determined according to the water resistance of the writing.

2. Resin solution method:

It is a method of spraying natural or synthetic resin solution on the document to strengthen it. The selected resin solution should have the following properties:

(1) Colorless, transparent, and does not discolor itself.

(2) It has no side effects on writing, color and fiber.

(3) It has a certain bonding force and is resistant to aging.

(4) It is easily reversible, does not become hard after treatment, and feels good.

The following types are used that meet the above conditions:

a Aluminum solution:

It is a Futong strengthening agent used for mounting calligraphy and painting, with a general formula The ingredients are: glue 3, alum 1, and water 70~80 grams. During the preparation process, the appropriate temperature (40~50°C) should be controlled. When using, use a pen to apply the solution on the reinforced paper. Apply one side first, then the other side, and the application should be even. Dip coating can also be used to dip the paper to be reinforced into a vitriol aqueous solution. Use should be based on specific circumstances.

b Synthetic resin solution:

As early as the 1940s, cellulose acetate was used to strengthen paper. With the development of polymer chemistry, various new synthetic resins are constantly coming out, including polyvinyl alcohol and acrylic resin. However, since the aging degree of these resins and their impact on writing and paper have not been thoroughly studied, they are still not widely used.

3. Adding film method

Adding film method adds a layer of resin film (such as cellulose acetate, polyester, polyethylene, nylon, etc.) or transparent film on both sides of the fragile paper. Net to strengthen the paper. There are many methods of coating, including hot pressing coating method, solvent coating method, vacuum coating method and silk screen reinforcement method. The various methods are now introduced as follows:

(1) Hot pressure coating method:

The hot pressure coating method was developed by Barrow and Scribner of the United States in the 1930s. Research success. This method uses a transparent resin film (cellulose acetate, polyethylene, polyester, polycarbonate, nylon, etc.) to sandwich the paper document in the middle. It is reinforced by hot pressing. This method has been widely used in foreign archives, libraries, and museums. Examples are as follows:

The U.S. Library of Congress uses a flat plate water pressure membrane method to sandwich documents between two sheets of acetic acid. Put the cellulose film in the middle into a film adding machine, heat it to 140~150°C, and reinforce it under a pressure of 22-36 kg/cm2.

Romanian Archives: Polyethylene film, Japanese tissue paper, and cellulose acetate are used as reinforcement materials. There are two reinforcement methods. One is the hot pressing method, which requires cleaning the documents first. Cover with polyethylene film in the middle and Japanese tissue paper on top, then put it into a flat-plate hydraulic laminating machine, control the temperature at 130°C, and the pressure at 14 kg/cm2, and wait for one minute. But it should be noted that before the reinforcement is fed into the laminating machine, a layer of drawing paper must be placed on both sides. The second is the cold pressing method, which uses a 5% cellulose acetate acetone solution, sprays it on the document, covers it with Japanese tissue paper, and then uses a press to press and solidify it.

The British Qiuyuan Archives adopts different reinforcement methods according to different situations of damaged documents. If the reinforcement object is thick paper, Japanese paper is used for reinforcement, parchment paper is pasted with kraft paper, and broken documents are first After filling the gaps with Japanese paper, add silk, adhesive paper, and tissue paper, and then put them into a laminating machine for hot pressing and reinforcement. The number of bonding layers on both sides of the document can be determined based on the damage.

At the Louvain Provincial Archives in France, damaged documents are first filled with tissue paper, then transparent celluloid paper is added to both sides of the document, paper nylon film is bonded, and then placed in a laminating machine with a temperature control of 180 ℃, just perform hot pressing.

(2) Moran film method:

Proposed by the British Moran Plastics Company, the method is to place the document in the middle of the cellulose diacetate or cellulose triacetate film , use a controllable electric iron, control the temperature to 80°C, and apply slight pressure. The advantages of this method are that it does not require expensive film adding machines, the heating temperature is low, and it is easy to use.

(3) Disproga membrane method:

This is a method successfully studied by the London Museum. They chose an acrylic resin coated on the back of Disprog gauze paper as the book laminating material. This is a cold laminating method, and the designed laminating machine can handle less than 20 inches. file. According to reports, the effect of adding film is very satisfactory.

The coating methods introduced above are all through hot pressing. Due to the high cost of equipment and the damage to documents caused by high temperatures, in order to make up for these shortcomings, the National Archives of India proposed to use solvents to dissolve the film. Method: First cut the reinforcement materials to the required size and place them in the following order. Then brush an appropriate amount of acetone on the surface of the interlayer to spread the acetone solution from the center to the edges. Then use an ordinary book press to press the film and let it dry. It is a widely used reinforcement method.

4. Vacuum coating method

The vacuum coating method is to place the paper in a stainless steel vacuum container, pass the monomer under vacuum conditions, and penetrate into the paper fibers. A protective layer (polymer-paper-polymer) is formed on the paper to enhance the strength of the paper and reinforce the paper.

Commonly used monomers include ethyl acrylate, methyl methacrylate, acrylic acid, dimethyldichlorosilane, p-xylene, etc. Currently jointly researched by Nanjing Museum and Nanjing Library, the application of parylene (Paralon N) shaped coating technology on paper is a relatively advanced paper reinforcement technology. This method is now introduced as follows:

Parylene, also known as Paraxylene N (PPX-N), was first developed by the American Carbonization Company as early as 1951. Using xylene as raw material, polyparaxylene film is produced by vacuum cracking method. Industrial production began in 1965. In order to improve its burial performance, there are also monochlorinated and dichlorinated paraxylene.

Parylene is a thermoplastic that has the stability of aromatic groups and the flexibility of aliphatic chains, so it can be as thin as 0.25 microns without cracking. The polymer absorbs almost no visible light and is therefore colorless and transparent. The polymer is extremely resistant to chemical attack and is insoluble in most commonly used chemical reagents. Can remain stable under high temperature conditions. Because of these excellent properties, this technology has attracted more and more attention.

(1) Polymerization method of polyparaxylene:

Use paraxylene as raw material, dilute it with water vapor, and heat it through a reaction tube at 900~950°C under reduced pressure. Solution, maintaining the superheated cracked steam (. H2C--CH2.), and the un-cracked P-X, through the condenser tube cooled by air, the steam is reduced from 900°C to 145°C-150°C, Then enter a boiling distillate bath equipped with a condensation reflux pipe and connected with a water separator, and then filter, reduce pressure, distill, quench, filter again, and dry (vacuum drying) to obtain high Pure crystalline polyparaxylene (PPX-N). The reaction is as follows:

(2) Vacuum deposition of parylene (application)

The vapor deposition process of parylene is similar to vacuum coating of metal in some aspects. The only differences are the required vacuum requirements. The deposition process consists of the following three steps. The first step is the vaporization of the solid dimer at around 160°C. The second step is that when the dimer is around 680°C, two pairs of methylene-methylene groups undergo massive pyrolysis to generate monomer diradicals. Finally, the monomer enters the room temperature vacuum deposition reaction chamber, and the monomer is absorbed by the paper. . Polymer bridges will be generated at the contact points between paper fibers and fibers, increasing the overall strength of the entire paper. The degree of strength increase increases with the thickness of the polymer. However, if the thickness is too thick, it will become brittle. It is generally believed that a covering thickness in the range of 2.5 ~ 7.5 μm will maintain or even increase flexibility while obtaining desirable strength.

(3) Effect of reinforcement

a. The treated paper and the untreated paper were tested for folding strength. The result: the untreated paper folded only 85 times. It has been damaged, but the paper treated with Paralon N has been folded 1,000 times without any signs of folding at the corners. Microscopic examination of the creases revealed that most of the paper's individual fibers had been damaged and that the corners were held together by polyparaxylene bridges.

b. In order to test the barrier properties of the treated paper, the treated and untreated paper strips were soaked in water for six months. As a result, the unburied paper strips became translucent and brown. Black, soft and brittle.

The treated paper showed no signs of decay.

c. After 6 months of aging test, the untreated paper turned white and brittle. The treated paper has not turned white or broken at all, only some wrinkles have appeared. The paper is still strong and flexible.

d. In order to measure the resistance of treated paper to chemical reagents, the paper sample was soaked in 70% sulfuric acid solution for 24 hours. The paper sample turned yellow, but the covering layer prevented the paper from being damaged. Its strength and flexibility are still very good.

This method has been applied in research on book reinforcement in American libraries and has achieved gratifying results. It has been successfully used in coating wooden crafts, insect specimens, feather products, shells, minerals and plant specimens. With the deepening of research work, the application of this technology in the fields of books, archives, and cultural relics protection will play a greater role.

5. Silk mesh reinforcement method:

Silk resin mesh is a new type of reinforcement material, suitable for the reinforcement of fragile thin papers and textile cultural relics, such as tissue paper, raw edge paper, and history. Paper, glossy paper, newsprint. It is especially suitable for the reinforcement of writing or printing paper on both sides, and it is also suitable for the reinforcement of documents whose writing has been infiltrated by water.

The method is: first smooth out the wrinkles of the reinforcement object, align the breach, and add a small strip of wire mesh to the breach to connect it into a whole. On the bottom of the laminator, lay a flat layer of wool felt, then overlay the reinforcements on top. When the automatic temperature indicator of the laminator reaches 80°C, apply slight pressure. Follow the same method on the other side. When operating, attention should be paid to the fact that the screen must be flat, and the mesh should be perpendicular to the lines of text. Press the iron in order and do not skip the flowers to avoid wrinkles on the screen. The force should be even and the iron will pass through. The heat temperature is generally controlled at around 80°C. If the temperature is too high, it will affect the paper. If the temperature is too low, it will not be easy to bond. The operation should be flexibly controlled. This technology has been widely used in museums, libraries, and archives. A large number of precious paper cultural relics were rescued.