One question we are asked more than any other is what is the difference between bookbinding adhesives. When for example do you use paste rather than PVA/EVA and in what circumstances is one type of adhesive more suitable than another. To answer this question we need to understand the properties of the adhesives.
Modern bookbinding adhesives, principally PVA and EVA have been in common use since the 1970’s and replaced the older hot glues, sometimes referred to as ‘Scotch’ or animal glue which were made from bones and hide. The option to use the modern white glues has several advantages.
So when to use them?
PVA and EVA
Both PVA and EVA can be used for almost all binding processes that involve cloth and paper. PVA (Poly Vinyl Acetate) and EVA (Ethylene-vinyl Acetate) have very little odour and they are instantly ready for use and are quick drying. EVA is also reversible in water.
Shepherds recommend a type known as EVA which as well as being very strong is also flexible which makes it ideal for gluing up and lining spines that must be able to bend and move easily when the book is opened.
But EVA and PVA’s fast drying time requires you to work quickly and although you can thin them down with water, most binders prefer to use a small amount of paste mixed in to prolong the open time and make it easier to use. This is particularly useful in hot weather or in very dry atmospheres. You can also buy a ready mixed 50/50 of EVA and paste from shepherds for all round use.
All modern white glues are water based, have no dangerous components and a normal storage life of six months providing they are kept in sealed containers between 7oC and 30oC.
Many professional bookbinders make their own paste, particularly those working in the traditional way with leather and fine binding. A simple paste can be made from wheat starch and water and will last several days when refrigerated or you can buy ready made starch and rice pastes from suppliers such as shepherds and Hewit.
Because of its much higher moisture content paste has a far longer open time or drying time. This is particular important when applying adhesive to a large area, such a big sheet of paper.
Binders also often prefer paste to EVA in situations where they require good ‘slip properties’. The additional moisture gives more time for adjustment without the adhesive drying too quickly. The disadvantage of the longer drying time is that the binding process is inevitably slower and you need to consider the effect additional moisture can have on different materials.
When you apply wet adhesives to materials the moisture content in the glue stretches the paper and as it dries the paper contracts and pulls the board into a curve. Because paste has a higher moisture content than PVA the stretch and contraction will be stronger so you will end up with a more pronounced curve.
To counteract this warping with either adhesive, and this is one of the golden principles of bookbinding , it is important to glue another material to the other side to pull it flat. For example when you make a cover the endpaper then pulls the boards flat when the book dries.
The most important thing is that you are comfortable in applying the adhesive, that it is easy to spread with the brush (or roller if you prefer) and that it doesn’t dry out before you have had time to apply adhesive to the whole surface. I would recommend practicing on a small area to see how the adhesive responds if you have the time and materials to spare. Like anything practice makes perfect and you will start to make your own informed decisions with the more experience you have.
As you progress with bookbinding you will find many circumstances where paste is preferable to EVA; this is particularly true in fine leather work and paper repairs. Many binders may use both Paste and EVA simultaneously, mixing them together according to need.
But for those of you working mainly with paper and bookcloth, PVA/EVA and PVA paste mix will cover most of your needs.
Hopefully this introduction to bookbinding adhesives has uncovered some of the mysteries and will help you make the right choice of adhesives for your projects.