For Emery Purposes—Very high-grade glue that has been carefully prepared to eliminate all acids, alkalies and impurities. A good emery glue possesses superior water-absorbing qualities. To test a glue for emery purposes, soak an ounce in about five times its weight of water at room temperature for 48 hours. If at the end of the time the water shows discoloration, or if decomposition is evidenced by a disagreeable odor, the glue is not adapted to emery use; otherwise it may safely be used. Weigh glue after the operation, to get an idea of its water-taking properties.
HOW MUCH TO PAY FOR GLUE
While the high test glues cost more per pound, they go farther and do better work, except in cases when their quick-setting characteristics are an objection.
How much you can afford to pay for your glue is a question that you must answer from your own observation and tabulation of results. In certain lines it would be foolish to use a high-grade glue, where the work would not benefit in proportion to the increased expenditure. Any attention given to the subject will be well repaid.
KEEP ACCURATE RECORDS
Always keep accurate records, and base your future purchases upon the demonstrated comparative results already attained by the various glues you have used in actual practice.
No glue is good to use unless properly prepared. A 16-cent glue may be reduced to the grade of an 8-cent glue by overheating. The grade of the glue at the time it is used is the important thing.
Do not by faulty methods of preparation impair the working quality of your glue. A glue of moderate high-grade properly prepared is better for practical purposes than a high-grade glue whose working quality has been destroyed by excessive or prolonged heating.
WATERPROOF GLUE
Sometimes it is desired to use glue with waterproof qualities. Glue is rendered practically waterproof by adding a small quantity (about 1%) of ammonium or potassium bichromate to the glue liquid. Upon hardening, the glue then becomes waterproof. Adding a small quantity of formaldehyde to the liquid glue will help it to resist the action of water after it has dried for some time.