Mouth Glue

227. Mouth Glue affords a very convenient means of uniting papers, and other small light objects; it is made by dissolving by the aid of heat, pure glue, as parchment glue, or gelatine, with about one quarter or one-third of its weight of coarse brown sugar, in as small quantity of boiling water as possible; this, when perfectly liquid, should be cast into thin cakes on a flat surface very slightly oiled, and as it cools cut up into pieces of a convenient size. When required for use one end may be moistened by the mouth, and is then ready to be rubbed on any substances it may be wished to join; a piece kept in the desk or work-box is exceedingly convenient. (See 63.)

Paste

228. Paste is usually made by rubbing up flour with cold water and boiling;a little alum is mixed before boiling it is much improved, being less clammy, working more freely in the brush and thinner, a less quantity is required, and it is therefore stronger. If required in large quantity, as for papering rooms, it may be made by mixing one quartern of flour, one quar-ter pound of alum, and a little warm water;when mixed, the requisite quan-tity of boiling water should be poured on whilst the mixture is being stirred. Paste is only adapted to cementing paper; when used it should be spread on one side of the paper, which should then be folded with the pasted side inwards and allowed to remain a few minutes before being opened and used; this swells the paper, and permits its being more smoothly and securely attached. Kept for a few days, paste becomes mouldy, and after a short time putrid;this inconvenience may be obviated by the use of

229. 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.

230. Liquid Glue

Several prepa-rations were much in vogue a few months since under this title. 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. Of the use of common glue very little need be said;it should always be prepared in a glue-pot or double vessel, to prevent its being burned, which injures it very materially;the 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 inconvenience can be obviated by employing in the outer vessel some liquid which boils at a higher temperature than pure water, such as saturated so-lution of salt (made by adding one-third as much salt as water). This boils at 224° Fahr., twelve degrees 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. (See 66.)