By Snow Fain

It is easy to understand how a tear can happen in books due to the age of the book and through handling. This post will review why a tear can occur and an explanation as to how and why the tears are treated.

The Tear

One might shed a tear for a tear, but it is a common occurrence when it comes to paper. Some of the most common sources of damage to paper, especially old paper, are mold, insects, moisture and careless handling. Mold, insects and moisture over time weaken the paper, which can cause tears to occur more easily. When handling a book, many things can cause tears to occur, such as turning the pages too quickly, folding the corners to a mark a page, or the brittleness of the paper through age.

When a tear occurs, there are small losses that cannot be seen by the naked eye. Trying to put the tear back together will not be perfect because the surface is irregular. Mending the tear helps fill those tiny areas of loss so the paper fits back together as seamlessly as possible.

This post will focus on one method of mending tears with Japanese paper and wheat starch paste. There are other techniques for mending a tear, but these basics will provide a good start.

The Tear Repair


  1. Japanese Paper

The type of paper used for a tear repair varies from object to object. Japanese paper is made with different types of fiber and are a variety of thicknesses (Image 1). The type of Japanese paper chosen for the tear is specific to each paper being mended. What is fundamental with mending is that the paper used to mend should be weaker than the object. The repair, if it should tear, should tear before the object as well as not to expand and contract more dramatically than the object so the object breaks before the repair. That is one of the purposes for the repair, to prevent further damage to the object. It can be either handmade paper or machine-made paper as long as it matches the requirements for the tear that is being treated.

One of the main reasons for using Japanese paper is the characteristic of the paper. The front and back of the Japanese paper are slightly different in that one side has a little more texture, roughness, than the other. The side that has the texture will be face down to the tear. The fibers (Image 2) of the Japanese paper will link with the fibers on the paper being treated. This will make a strong but gentle bond within the repair on the surface. The Japanese paper acts as a patch for the tear (Image 3).

Image 1: Variety of Japanese papers

Image 2: Detail of the fibers of trimmed Japanese paper

Image 3: Japanese paper before adhered to the surface with the textured side down

  1. Wheat Starch Paste

The key component to tear repairs is the wheat starch paste. The consistency of the paste does depend on the materials that are chosen, and the state the paper is in during treatment. The paste is more than just a layer between the object and the Japanese paper. The paste will go between the fibers of both the Japanese paper and the object being treated. The paste will go where the Japanese paper cannot and flow into those irregular areas caused by the tear.

To understand why the paste is so important, there must be an explanation as to how the paste is made and how it works. Wheat starch, before it is cooked into paste, is a fine powder with the consistency of flour or powdered sugar. It is made up of small circular-like granules that keep their shape until heated in water. The way to produce the sticky paste is to stir the starch in water over heat. The process of making paste is like following a recipe, but like any recipe, most people have their own recipe they follow.

The amount of time, stirring and the temperature while making paste can vary, and this variation will also cause the paste to vary in thickness and stickiness. As discussed in the Handbook of Water-Soluble Gums and Resins, this is so because the small circular-like granules are heated in the water, which causes them to swell and the stirring encourages the granules to break (Illustration 1). The granules break because the attraction that was keeping their shape together was weakened by all of this interaction. Not all the granules will break during this time, so there will be a mixture of granules at different stages within the paste. This type of paste mixture of water, and the variety stages of the wheat starch granules is called a viscous (thick) dispersion.

Illustration 1: This illustration shows how the starch granules react when heated in the water. The granules expand and swell and some burst under the pressure. The final panel shows different granules at different stages in the heating process, which follows the definition of a viscous dispersion.

At this stage the paste has become thick due to the granules swelling and needs to cool. The cooling of the paste is just as important as the heating. The rate at which the paste is cooled will also affect the outcome of the paste. The paste should be stirred while cooling, but if the paste needs to be thick there should be less stirring so the granules are not broken down any further. If the granules are over-mixed, the thickness and stickiness of the paste will decrease.

After the paste has cooled to room temperature, it should be pressed through a damp hair sieve. This will make the paste smooth so applying the paste to surface will be a more even application. If the paste is still not at the desired consistency, mixing in more water will dilute it. Images 4-14 demonstrate one method of how wheat starch paste can be prepared.

Images 4-6: (Left to Right) (4) the starch in a beaker before cooking, (5) the starch after the addition of water on the hot plate, and (6) the paste starting to form after heat and stirring.

Images 7-10: (Left to Right) (7) After the paste has reached its desired thickness (viscous dispersion) it is cooled by placing the hot pot in a bowl of cool water and continue stirring, (8) after the paste is completely cooled, (9-10) the paste is then pressed through a hair sieve.

Images 11-14: (Left to Right) (11) The appearance of the paste after going through the sieve, (12-14) the paste can then be used or can be diluted to the desired consistency.

It can be used for the tear repair at this time. This type of paste when applied to the surface will dry by the water evaporating and leaving the solid (the wheat starch) behind as explained in Science for Conservators: Adhesives and Coatings Vol. 3. The paste will find those areas where the Japanese paper cannot go when applied to the tear (See Illustration 2).

Illustration 2: This illustration shows where the paste will flow after it is applied.

  1. Tools

Image 15 :Example of tools used for completing a tear repair. A: Ruler. B: Palette Knife, C: Tweezers,       D: 8oz Weight, E: Brushes, F: Water Pen, G: Scalpel, H: Blotter Paper, I: Bondina, J: Wheat Starch Paste,    K: Japanese Paper, and L: Glass Tile.

The tools (Image 15) used for a tear repair can vary, but one piece of equipment is necessary: tweezers. Tweezers allow for a precise placement of the Japanese paper over the tear being treated. A palette knife is used to mix the wheat starch paste on the glass plate. The brush is used to apply the paste onto the Japanese paper. The tweezers because once the paste is brushed on the Japanese paper, it can be difficult to remove without the tweezers from the glass surface to place on the tear. The ruler is for measuring the tear and to help cut the Japanese paper to the appropriate size for the tear. The Bondina® and blotter paper pieces are used once the repair has been placed. The blotter paper soaks up the extra moisture from the Japanese paper, and the bondina acts as a barrier between the object and blotter so they do not stick to one another. The weight is placed on top of the blotter to add a small amount of pressure so the paper will not wrinkle as it dries.


The wheat starch paste and the Japanese paper work together to complete the repair. From the discussions of the Japanese paper and the wheat starch paste, it is now time to make some decisions concerning repairing the tear.

The treatment is thought out with every step. The Japanese paper must work well with the paper the object is made from. It cannot be stronger than the object as discussed in the Japanese paper section. The wheat starch paste must complement the materials being used, and not overpower the Japanese paper or the object.

Images 16-24 show the steps through a tear repair.

The great thing about wheat starch paste is that it can be reversed. The treated area can be moistened with water to reactivate the paste. This will allow the treatment to be redone if it did not work correctly the first time and needs to be amended.

Images 16-17 : The tear is examined before any treatment. The tear is measured, and the paper of the object is compared to the Japanese paper.

Image 18 :The Japanese paper chosen should be weaker than the paper of the object.

Image 19: To prepare, Bondina and blotter paper are placed under the tear being mended.

Image 20: The cut Japanese paper has the fibers along the edges. The wheat starch paste is applied to the textured side from the center out, so the fibers stick out.

Image 21: The Japanese paper is placed textured side down, and brushed with a soft bristle brush to push the fibers down onto the surface.

Image 22: Another layer of Bondina and blotter paper are placed on top of the repair with a small weight.

Image 23: Once the repair is dry, the Japanese paper can be trimmed flush with the object.

Image 24: The completed tear repair.

All is mended

In conclusion, it is more than just the appearance of the object, but about the importance of understanding the materials, what it is made of, and how to use it properly. The wheat starch paste flows in between the fibers of the object and the Japanese paper, creating that stronger bond between the two layers. Completing a tear repair involves many steps and each material used on the object cannot be overlooked. The damaged object cannot be fixed completely, but it can be treated to prevent more damage in the future.