Permanent Paste, made by adding to each half-pint of flour paste without alum, fifteen grains of corrosive sublimate, previously rubbed to powder in a mortar, the whole to be well mixed; this, if prevented from drying, by being kept in a covered pot, remains good any length of time, and is therefore convenient; but unfortunately it is extremely poisonous, though its excessively nauseous taste would prevent its being swallowed accidentally. It possesses the great advantage of not being liable to the attacks of insects.
2491. Liquid Glue
The liquid glue of the shops is made by dissolving shellac in water, by boiling it along with borax, which possesses the peculiar property of causing the solution of the resinous lac. This preparation is convenient from its cheapness and freedom from smell; but it gives way if exposed to long-continued damp, which that made with naphtha resists.
2492. Common Glue
Of the use of
common glue
very little need be said; it should always be prepared in a gluepot or double vessel, to prevent its being burned, which injures it very materially. The chief objection to the use of this contrivance is, that it renders it impossible to heat the glue in the inner vessel to the boiling point; this, however, can be obviated by employing in the outer vessel some liquid which boils at a higher temperature than pure water, such as a saturated solution of salt (made by adding one-third as much salt as water). This boils at 224° Fahr., 12° above the heat of boiling water, and enables the glue in the inner vessel to be heated to a much higher temperature than when pure water is employed. If a saturated solution of nitre is used, the temperature rises still higher.