Glaze for Porcelain

Felspar 27 parts, borax, 18, Lynn sand 4, nitre 3, soda 3, Cornwall china clay 3 parts. Melt together to form a frit, and reduce it to a powder, with 3 parts of calcined borax. - Rose.

Glue is made by boiling parings of ox-hides and other skins in water, evaporating the solution to a due consistence, allowing it to gelatinize in wooden boxes, cutting it into layers with a wire, and drying the layers on nets stretched on wooden frames. Bones also yield a pale glue, described under Gelatin. Bank-note glue, or mouth glue is made by dissolving 1 lb. of fine glue, or gelatin, in water, evaporating it till most of the water is expelled, adding 1/2 lb. of brown sugar, and pouring it into moulds. Some add a little lemon-juice. It is also made with 2 parts of dextrin, 2 of water, and 1 of spirit.

Liquid Glue

1. Dissolve bruised orange shell-lac in 3/4 of its weight of methylated or rectified spirit, or of rectified wood naphtha, by a gentle heat. It is a very useful as a general cement and substitute for glue. 2. Another kind may be made by dissolving 1 oz. of borax in 12 oz. of soft water, adding 2 oz. of bruised shell-lac, and boiling till dissolved, stirring it constantly. 3. Dissolve 1000 parts of glue in 1000 parts by weight of water in a glazed pot, over a gentle fire. When it is melted, add nitric acid (sp. gr. l.32) 200 parts, pouring it in very gradually. An effervescence is caused by the escape of hyponitrous acid. When all the acid is added, allow the mixture to cool. (This glue is found to remain unaltered on exposure to the air. It is applied cold, and is recommended as very convenient in chemical operations.) M. Dumoulin.

Marine Glue

Cut caoutchouc into small pieces, and dissolve it, by heat and agitation, in coal naphtha. Add to this solution powdered shell-lac, and heat the whole with constant stirring, until combination takes place, then pour it while hot on metal plates, to form sheets. When used it must be heated to 218° F., and applied with a brush.

Glue of Casein

1. Braconnot. Dissolve casein in a strong solution of bicarbonate of soda. 2. Wagner. Dissolve casein in a cold saturated solution of borax. Superior to gum, and may take the place of glue in many cases. May be used for the backs of adhesive tickets.

Vegetable Gluten

Form wheat flour into a stiff paste with cold water; then knead it under a stream of water till all the starch is washed away. What remains is impure gluten.

Golden Compound

Anhydrous tungstate of soda, or the salt obtained in fusing 2 equivalents of tungstic acid with 1 of carbonate of soda, is to be melted in a porcelain crucible, over a spirit lamp, at a temperature not more than sufficient; then add small pieces of pure tin to the melted mass. Cubes of a golden colour instantly form. The process should not be continued too long, or they acquire a purple hue. (See Aurum Musivum.)

British Gum

(See Dextrin.) It is also prepared by heating starch alone, or previously mixed with an acid. Pinel directs half a gallon of nitric and half a pint of hydrochloric acid to be mixed with 100 gallons of water, and as much potato fecula added as will form a paste. In 2 hours remove the paste in buckets, prepared for the purpose, to drain off all the water. Then place the paste in small lumps in a drying room till dry; pulverize it, and expose the powder the first day to the temperature of 100°, the next day raise it to 150°, on the third clay to 190°. It is then powdered, sifted, and heated from 300° to 350°. To give it the appearance of gum, after it has gone through the stove, and is powdered and sifted, mix it to a paste with water to which 1 per cent. of nitric acid has been added, spread it on copper plates in layers 3/4 of an inch thick, and heat it in an oven from 240° to 300°, then remove it to the open air to cool.