Before cementing vulcanized rubber the surface should be roughened or still better it may be seared with a red hot iron. For bicycle tyres this is especially to be recommended.

Cement for Cuts in Bicycle Tyres, Rubber Belts, etc.—Carbon bisulphide, 5 ounces; gutta-percha, 5 ounces; caoutchouc, 10 ounces; fish glue, 2½ ounces. After it is applied and has dried the excess can be removed with a wet knife. Bad cuts should first be stitched up.

Bicycle Tyre Cement to fasten Tyres to Rims.—Equal parts of pitch and gutta-percha are melted together. Sometimes two parts of pitch are prescribed. This cement has extended application.

Cement for Paper Boats and for Mending Rubber Goods.—Fuse together equal parts of pitch and gutta-percha, and to this add about 2 parts of linseed oil containing 5 parts of litharge. Continue the heat until the ingredients are uniformly commingled. Apply warm.

Waterproof Cement.—Shellac, 4 oz; borax, 1 oz; boil in a little water until dissolved, and concentrate by heat to a paste.

Another.—10 parts of carbon disulphide and one part of oil of turpentine are mixed, and as much gutta-percha is added as will readily dissolve.

Cement for Mending Hard Rubber.—Fuse together equal parts of gutta-percha and genuine asphaltum; apply hot to the joint, closing the latter immediately with pressure.

Glue to Fasten Leather, etc., to Metals.—1 part crushed nut galls digested 6 hours with 8 parts distilled water and strained. Glue is macerated in its own weight of water for 24 hours, and then dissolved. The warm infusion of nutgalls is spread on the leather; the glue solution upon the roughened surface of the warm metal; the moist leather is then pressed upon it and dried.

Marine Glue, Various Formulæ.—I. Dissolve 1 part of india rubber in 12 parts of benzole, and to the solution add 20 parts of powdered shellac, heating the mixture cautiously over a fire. There is great danger of conflagration. Apply with a brush.

II. Caoutchouc, 1 oz; genuine asphaltum, 2 oz; benzole or naptha, q. s. The caoutchouc is first dissolved (as described in chapter XII.), and the asphaltum is gradually added. The solution should have about the consistency of molasses.

Cement for Vulcanized India Rubber.—Stockholm pitch, 3 parts; American resin, 3 parts; unmixed india rubber, 6 parts; oil of turpentine, 12 parts. Heat and mix very thoroughly. More oil of turpentine may be added as required.

Gutta-Percha Cement for Leather.—Soak gutta-percha in boiling water. Soften in benzole after cutting up for a day. Heat on a water bath until the greater part of the benzole is expelled. When cool it will solidify. Use by heating.

Cement for Rubber Shoes.—

For first solution dissolve by mastication. For second, melt the finely divided gum with the resin, add the Venice turpentine and finally the oil of turpentine. Use heat if necessary. Mix both solutions finally. To apply, saturate a piece of linen with the cement and apply to the spot previously coated with the cement. As it dries apply a little more as required. A finishing varnish is given in the last chapter. Parkes’ cold curing process may be applied as described in chapter XI.

Chatterton’s Compound for uniting sheets of gutta-percha in cable cores and for general work with gutta-percha coated wires.—Stockholm tar, 1 part; resin, 1 part; gutta-percha, 2 parts.

Waterproofing for Wooden Battery Cells.—Resin, 4 parts; gutta-percha, 1 part; boiled oil, a little.

Another Formula.—Burgundy pitch, 150 parts; old gutta-percha in fine shreds, 25 parts; ground pumice stone, 75 parts. Melt the gutta-percha and mix with the pumice stone and then add the pitch, melting all together. Apply melted and smooth off with a hot iron.

Cement for Celluloid.—Shellac, 1 part is dissolved in spirits of camphor 1 part, with 3 to 4 parts strong alcohol. It is applied warm and the parts united must not be disturbed until the cement is hard.