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[BKARTS] Some adhesive basics



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Adhesives are such a broad topic that I'll only try to touch upon those most
commonly used in bookmaking. You might want to check out ADHESIVES AND
COATINGS in the Science for Conservators series, published by Routledge, for
a good overview.
There is no agreement upon what constitutes an "archival" adhesive.
Minimally an adhesive should be pH neutral, non-staining, chemically and
physically stabile over a very long period of time, biostatic, and easily
reversible with solvents which will not damage the materials being adhered.
No adhesive fully meets all of these criteria. Add to this questions of bond
strength, tack, working time, compatibility to other materials, etc., and in
practice one must use a range of adhesives, often altering and mixing them in
the shop to get closer to an ideal for a given process. If it is water based,
always use distilled water to make up or thin the adhesive.
PVA's or "white glues" can be gotten which are non-staining and pH neutral or
buffered, and bugs don't eat them, but their reversibility is not great
(adding methyl cellulose or wheat starch paste is thought to improve their
long term reversibility [actually only softening] with water). They are
relatively new and nobody fully knows the long term stability of the current
crop of PVA's. Elmer's is not the best choice.
Hot gun adhesives should be avoided if only for their lack of control. I
occasionally deal with objects which have been "repaired" with hot gun
adhesives and they have often not been easy or safe to remove.
Wheat starch and rice starch pastes have the great virtue of having been
around a really long time, and so their performance is well documented. They
have many drawbacks, however. Bugs and microorganisms like to eat them, they
are not always as easily and fully reversible as many seem to believe, and
they can make some materials more brittle over time. But their compatibility
to many materials and the ability to easily alter their working qualities
make them very useful. I'm not fully comfortable with the biocides often
added to starch adhesives and so avoid them.
Methyl cellulose has many of the virtues and fewer of the disadvantages of
starch pastes. It has a lower tack and forms somewhat weaker bonds, and this
with it's clear color especially recommend it for paper repair, lining,
mounting, and the sizing of materials. It is often used as an admixture to
alter the working qualities of other adhesives, especially PVA. There are
several types of methyl cellulose, each with somewhat different properties.
For example, some types exhibit greater bond strength but form more brittle
films than others. It is made up by dissolving the powder in water using a
blender, and you should check the manufacturer's suggestions. Again, because
they are relatively new, their long term performance is not fully known, but
they are considered the safest bet of the newer adhesives.
Usually hot melt (as opposed to cold) hide glues are used in bookwork.
They've been around a long time and they have many properties which make them
very useful in binding, but their drawbacks are legion. Bugs love them, they
stain, they become brittle over time, often they are acidic. I don't believe
they should ever be allowed to come into contact with the text block if used
at all.
A good gelatin (as recently discussed onlist) is currently considered to be
preferable to hide glue in gluing up the spine of a textblock. I purchase
mine from chemical supply houses so as to insure the purest product
available.
Lastly, the phrase "less is more" should have been invented specifically for
adhesive use and application. Best,

James


James Tapley
Hand
Bookbinder
2077 Thirteenth Street
Sarasota, FL 34237
USA
Tel 941 366 8248

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