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ADHESIVES
When selecting an adhesive, consider its properties. First, is it safe for use on archival or research materials, and second, will it do the job.
Adhesives should be neutral pH and be made from ingredients that won't discolor or stain even after months or years. The repair should be long lasting yet easily reversible
without causing damage to the materials.
No one adhesive is suitable for all purposes but a small mending facility can accomplish a great deal with just a few kinds. The most useful are polyvinyl acetate (PVA),
methyl-cellulose, and wheat, rice or corn starch paste.
PVA
Recommended Polyvinyl Acetateadhesives are Jade 403 or Elvace, or other neutral pH PVA sold by conservation suppliers. When used out of the bottle, it dries too fast for most
uses. It is sometimes used straight for making enclosures. For most other uses, it is mixed with a slower drying adhesive, such as Methyl Cellulose, to provide a longer working time.
Methyl Cellulose
Made from cotton fibers treated with an alkali; it is sold as a white powder to be mixed with water by the user. It is not as strong as starch paste but is a perfectly
suitable and safe adhesive for the type of paper mending carried out in most libraries and archives. See mixing instructions below.
Starch Paste
Paste is made from the precipitated starches of wheat, rice and corn. It comes as a white powder that must be cooked to prepare it for use. It can spoil quickly, especially in
warm weather, but can be kept for short periods in a covered container in the refrigerator. Once it separates and becomes watery, it loses its adhesive properties and should be thrown out.
UHU and other glue sticks
Suitable for making enclosures, attaching bookplates and other uses on circulating materials. Some dry up in time and release their hold. Not for use on any archival or
rare materials. Many glue sticks are labeled "Acid-Free", however, some of the glues are extremely alkaline and are very damaging to paper and especially to photographic materials.
Pressure sensitive tapes
The adhesive on most tapes stains paper in time. It usually requires solvents to remove. Newer pressure-sensitive tapes may be advertised as being acid-free or archival but
they may be overly alkaline and they are difficult to remove. Commercially made products change without notice or warning so, even if a miracle tape existed today, there is no guarantee that it would be
the same in the future.
Rubber cement
Never use it! It gives off toxic gasses that are harmful to the worker. As it ages, it dries up, releasing its hold and staining paper. It damages paper irreversibly.
RECIPES
Methyl-Cellulose
Sprinkle 5 tablespoons methyl-cellulose powder into 1 cup of very hot water. Stir briskly to prevent lumps. When the powder is thoroughly dispersed, add enough cold water to make one quart. Let sit for several hours; preferably overnight. To thin, add a few drops of water, mix, let stand. When ready to use, decant a small amount into a heavy, wide-mouth jar. Never dip the brush into the main supply. Thick methyl-cellulose can be used for mending paper with Japanese tissue and to clean off the spines of books. The mixed adhesive will last for months if kept clean.
Fifty/fifty mixture of PVA and Methyl Cellulose (Mix)
Mix equal parts prepared methyl-cellulose and PVA. The mixture is easier to apply with a brush than plain PVA; it dries more slowly, giving the user more working time. Use the
mix for most work on book covers, pamphlet binders or enclosures.
A 50/50 mix of PVA and Methyl Cellulose is now available from a maker of fine papers and stationery, Twinrocker Handmade Paper. A PVA/paste mix, which has similar
characteristics, is sold by Conservation Resources International (See Suppliers List)
Starch Paste
Make a slurry of two tablespoons starch paste powder and a few teaspoons of cold water in a large pyrex cup or bowl. Pour approximately one cup of boiling water into the slurry while stirring briskly. It should thicken and become translucent. Put the mixture in the microwave, cook a couple of minutes, take out, whisk, cook another couple of minutes, etc. until paste is smooth and tacky. Let cool. Keep the main supply in the refridgerator; it may keep for a week or ten days, depending on weather and how clean the storage container was when the paste was put in it. When needed, take a small amount and sieve it (or strain through a double layer of damp cheesecloth). If it's too thick for your application, add water a few drops at a time and stir to achieve desired consistency and smoothness.
Paste can also be made on a hot plate or stove. A double boiler is ideal, otherwise, use a teflon-coated pot. Make a slurry of two tablespoons starch paste powder and a few
teaspoons of cold water. Pour approximately one cup of boiling water into the slurry while stirring briskly. Mix constantly during cooking, to prevent formation of lumps and to keep it from sticking or burning. The technique is similar to making gravy.
Do not add any preservatives to paste. If you have only occasional need for a slow drying, easily reversible adhesive, it will probably be more efficient to keep a supply of
methyl cellulose on hand. It will last for several months if not contaminated.
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