Cornflour paste may be used directly after it is made, and will keep good under ordinary circumstances for about a week. Directly it gets hard or goes watery, a new batch must be made.
GLUE
It is important for bookbinders that the glue used should be of good quality, and the best hide glue will be found to answer well. To prepare it for use, the glue should be broken up into small pieces and left to soak overnight in water. In the morning it should be soft and greatly swollen, but not melted, and can then be put in the glue-pot and gently simmered until it is fluid. It is then ready for use. Glue loses in quality by being frequently heated, so that it is well not to make a great quantity at a time. The glue-pot should be thoroughly cleaned out before new glue is put into it, and the old glue sticking round the sides taken out.
Glue should be used hot and not too thick. If it is stringy and difficult to work, it can be broken up by rapidly twisting the brush in the glue-pot. For paper the glue should be very thin and well worked up with the brush before using.
The following is quoted from “Chambers’ Encyclopædia” article on Glue:—
“While England does not excel in the manufacture, it is a recognised fact that Scottish glue ... ranks in the front of the glues of all countries. A light-coloured glue is not necessarily good, nor a dark-coloured glue necessarily bad. A bright, clear, claret colour is the natural colour of hide glue, which is the best and most economical.
“Light-coloured glues (as distinguished from gelatine) are made either from bones or sheepskins. The glue yielded by these materials cannot compare with the strength of that yielded by hides.
“A great quantity is now made in France and Germany from bones. It is got as a by-product in the manufacture of animal charcoal. Although beautiful to look at, it is found when used to be far inferior to Scottish hide glue.”