Common glue and isinglass, equal parts, soaked for 10 hours in just enough water to cover them. Bring gradually to a boiling heat, and add pure tannin until the whole becomes ropy, or appears like the white of eggs. Buff off the surfaces to be joined, apply this cement warm, and clamp firmly.
Mix 10 parts bisulphide of carbon with 1 of oil of turpentine, and then add enough guttapercha to make a tough thickly-flowing liquid. One essential pre-requisite to a thorough union of the parts consists in freedom of the surfaces to be joined from grease. This may be attained by laying a cloth upon them and applying a hot iron for a time. The cement is then applied to both pieces, the surfaces brought into contact, and pressure applied until the joint is dry.
Another leather cement is made of guttapercha dissolved in bisulphide of carbon, the mixture being about the thickness of syrup; the parts to be cemented must be well coated, so as to fill the pores of the leather; then heat the cement and join the ends, hammering the parts until the cement is cold.
To cement leather to metal: Wash the metal with hot gelatine; steep the leather in an infusion of nut galls (hot), and bring the two together.
1 lb. guttapercha, 4 oz. indiarubber, 2 oz. pitch, 1 oz. shellac, 2 oz. linseed-oil; melted together; it hardens by keeping, and needs re-melting for use.
Leather to metal:
melt together equal parts asphalt and guttapercha, and apply hot under a press.
F. Sieburger recommends the following process by Fuchs. Digest 1 part crushed nut-galls with 8 distilled water for 6 hours, and strain; macerate glue with its own weight of water for 24 hours, and dissolve; spread the warm infusion of the galls on the leather, and the glue on the roughened metallic surface; apply the prepared surfaces together, and dry gently; the leather then adheres so firmly to the metal that it cannot be removed without tearing. ('Polyt. Notizblatt.')
Leather to Pasteboard. Strong glue, 50 parts, is dissolved with a little turpentine in a sufficiency of water, over a gentle fire; to the mixture is added a thick paste made with 100 parts of starch. It is applied cold, and dries rapidly.
A good cement for splicing leather for straps is gutta-percha dissolved in bisulphide of carbon, until it is of the thickness of treacle; the parts to be cemented must first be well thinned down, then pour a small quantity of the cement on both ends, spreading it well so as to fill the pores of the leather, warm the parts over a fire for about half a minute, apply them quickly together, and hammer well. The bottle containing the cement should be tightly corked and kept in a cool place.