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Varnishes (Solvents for India-Rubber)

Solvents for India-Rubber and Gutta Percha. 1. Benzine. There are two bodies sold as benzine or benzole: one obtained by distilling coal or coal-tar-the true benzine-used in making coaltar colors; the other, from petroleum, contains but little true benzine. They may be used instead of turpentine in mixing paints and the true benzine for varnishes. Commercial benzine will not generally do for varnishes; that from petroleum is much the cheaper. Either forms an excellent solvent for india-rubber. solvent; acts in the cold; is made by passing the vapor of sulphur over red-hot charcoal. 3. Chloroform is very good, but costly.

Turpentine acts slowly, and takes long to dry.

India-rubber should always be cut into fine strings or shreds before being submitted to the action of solvents.

Solvent for Old Paint or Putty.

Caustic soda, applied with a broom or brush made of vegetable matter. It is sold in the shop 2. Bisulphide of Carbon is an excellent rubber | as concentrated lye. To give a Drying Quality to Poppy Oil.

Into 3 lbs. of pure water put 1 oz. of sulphate of zinc (white vitriol), and mix the whole with 2 lbs. of oil of pinks, or poppy oil. Expose this mixture, in an earthen vessel capable of standing the fire, to a degree of heat sufficient to maintain it in a slight state of ebullition. When one-half or two-thirds of the water has evaporated, pour the whole into a large glass bottle or jar, and leave it at rest till the oil becomes clear. Decant the clearest part by means of a glass funnel, the beak of which is stopped with a piece of cork. When the separation of the oil from the water is effected, remove the cork stopper, and supply its place with the forefinger, which must be applied in such a manner as to suffer the water to escape, and to retain only the oil. Poppy-oil, when prepared in this manner, becomes, after some weeks, exceedingly limpid and colorless.

To give a Drying Quality to Fat Oils.

Take of nut-oil, or linseed-oil, 8 lbs.; white lead, snightly calcined, yellow acetate of lead (sal saturni), also calcined, sulphate of zinc (white vitriol), each 1 oz.; vitreous oxide of lead (litharge), 12 oz.; a head of garlic, or a small onion.

When the dry substances are pulverized, mix them with the garlic and oil, over a fire capable of maintaining the oil in a slight state of ebullition. Continue it till the oil ceases to throw up scum, till it assumes a reddish color, and till the head of garlic becomes brown; a pellicle will then be soon formed on the oil, which indicates that the operation is completed. Take the vessel from the fire, and the pellicle, being precipitated by rest, will carry with it all the unctuous parts which rendered the oil fat. When the oil becomes clear, separate it from the deposit, and put it into widemouthed bottles, where it will completely clarify itself in time, and improve in quality.

Another Method.

Take of litharge, 1½ oz.; sulphate of zinc, & of an oz.; linseed or nut-oil, 16 oz. The operation must be conducted as in the preceding case.

The choice of the oil is not a matter of indiffer ence. If it be destined for painting articles exposed to the impression of the external air, or for, delicate painting, nut-oil or poppy-oil. Linseedoil is used for coarse painting, and that sheltered from the effects of the rain and of the sun.

A little negligence in the management of the fire has often an influence on the color of the oil, to which a drying quality is communicated; in this case it is not proper for delicate painting. This inconvenience may be avoided by tying up the drying matters in a small bag; but the dose of the litharge must then be doubled. The bag must be suspended by a piece of packthread fastened to a stick, which is made to rest on the edges of the vessel in such a manner as to keep the bag at the distance of an inch from the bottom of the vessel.

A pellicle will be formed as in the first operation, but it will be slower in making its appearance.