I never realized how much adhesive is used in a traditional book. The standard adhesive is Polyvinyl Alcohol (PVA), but it gets expensive and a much more affordable and workable option is starch paste. You can make a good paper paste with flour, but for bookbinding, I prefer to use starch. Starch is inexpensive ($2/16oz), dries clear, and can be reworked. Wheat starch can sometimes dry with a slight yellow tinge. PVA has the disadvantage of staining some materials like linen cloth. On the other hand, starch paste is easy enough to clean up with a damp cloth.
I make my paste extra thick from the start and thin it down with water as needed. I make 2-4 tablespoons worth at a time. This yields about 6-10oz of paste–enough for 3-4 cloth covered books. I need to get a kitchen scale so I can use weight instead of volume. I get my starch from an asian food market and I have found that there is some variation in the amount of paste I can get from any given bag. My basic formula is 1 part starch to 3 parts water.
I pre-soak this mixture for 12-24 hours, though I’ll cut it to 2 hours in a pinch. The longer pre-soak seems to yield a paste that stays gelled longer. No batch of paste will last more than about 3-5 days. It will all eventually lose its texture and develop mold. When it does, dump it out–outside, or maybe in your toilet. Don’t put it down your sink. It’ll smell terrible and probably clog the drain, too.
After pre-soaking, heat it gently in a small sauce pot and stir continuously. A two tablespoon batch will thicken in about 10 minutes and be fully cooked in about 20 minutes. A four tablespoon batch will take about 25-30 minutes. A lot of this will vary by the size of the pot you use (bigger pot will usually cook it faster) and the temperature you use. After cooking, I put it in a plastic container to cool and then add calcium hydroxide via an eye dropper to bring the pH up to 7-8.
Before using it, I thoroughly mix it to a working consistency and apply it with a brush or putty knife.