INTRODUCTORY REMARKS ON WORKING METHODS AND MATERIALS.
The bookbinder works with quite a large variety of materials which are mostly what we might call" half made," that is to say, such materials as have already undergone some hand or machine process in order to make them fit for the work of the bookbinder. This is not the place to go into details as to the source of all these materials or the manner of their production: that may be seen in special treatises.
We separate into various groups the materials we use.
A.- MATERIALS FOR SEWING AND PASTING.
The bookbinder himself prepares his paste from wheaten flour and boiling water. Put in a shallow vessel, by preference a stone or enameled metal wash-basin, the quantity of flour required for about eight days, pour in as much water as will make a mixture by soaking and stirring of the consistency of honey. Add to it boiling, water, first slowly, then quicker, stirring all the time. It does not do to add the water too quickly, as that is likely to make the paste knotty or lumpy, because it cannot be stirred quickly enough and the gluten develops unequally. If added too slowly, the starch is not heated quickly enough and does not thicken sufficiently or not quickly enough, and the paste turns out too thin.
Good paste, when cold, should not be stiff like pudding, but should be easily worked with a brush. In order to prevent a skin forming on the top whilst cooling, pour over the paste as much cold water as will cover the surface immediately after the mixing with the boiling water; this water is afterwards poured off.
In summer when the paste is made, and whilst still hot, add a few drops of turpentine and mix well; this preserves the paste and keeps off insects. The addition of alum to the paste tends to make it watery, besides having no preservative properties.
If required, paste may be thinned by adding a little warm water. Potato flour is often used fraudulently for making paste, but this should only be taken when it is possible to use it up quickly, and not for books, but only for fancy goods, as this flour does not possess great adhesive powder and is unsuitable for leather.
Glue is made from the well known cake glue. The best English glue, although the dearest, is the cheapest to use. Good glue whilst soaking in water should still retain a certain degree of stickiness, must not be greasy, and should have no disagreeable smell. Glue if weighed before soaking and afterwards dried and again weighed should give no perceptible' loss in weight. Good glue should not have a disagreeable taste, and above all should not betray the presence of salt. .
To obtain the proper consistency in glue for bookbinding, a quantity of the cakes is taken and sufficient water poured over it to cover well. The next day the gelatinous mass is taken out of the water and dissolved in the glue pot by placing the softened glue in a pot standing in an outer vessel containing boiling water. Glue should never be boiled nor placed directly on the fire, as that causes the loss of the best part of its adhesive property.