Clearing solution. Saturated solution of alum, 20 ounces; and hydrochloric acid, 1 ounce.[p. 173] Varnish. Brush over the negative a solution of equal parts of benzol and Japanese gold size.
Plasters.—Court Plaster. Use good quality silk, and on this spread a solution of isinglass warmed. Dry and repeat several times, then apply several coats of balsam of Peru. Or,
On muslin or silk properly stretched, apply a thin coating of smooth strained flour paste, and when dry several coats of colorless gelatine are added. The gelatine is applied warm, and cooled before the fabric is taken off.
Plating.—Bronze coating. For antiques, use vinegar, 1,000 parts; by weight, powdered bloodstone, 125 parts; plumbago, 25 parts. Apply with brush.
For brass where a copper surface is desired, make a rouge with a little chloride of platinum and water, and apply with a brush.
For gas fixtures. Use a bronze paint and mix with it five times its volume of spirit of turpentine, and to this mixture add dried slaked lime, about 40 grains to the pint. Agitate well and decant the clear liquid.
Coloring Metals.—Brilliant black for iron. Selenious acid, 6 parts; cupric sulphate, 10 parts; water 1,000 parts; nitric acid, 5 parts.
Blue-black. Selenious acid, 10 parts; nitric acid, 5 parts; cupric sulphate; water, 1,000 parts. The[p. 174] colors will be varied dependent on the time the objects are immersed in the solution.
Brass may be colored brown by using an acid solution of nitrate of silver and bismuth; or a light bronze by an acid solution of nitrate of silver and copper; or black by a solution of nitrate of copper.
To copper plate aluminum, take 30 parts of sulphate of copper; 30 parts of cream of tartar; 25 parts of soda; and 1,000 parts of water. The article to be coated is merely dipped into the solution.