Wash the metal with hot gelatine; steep the leather in an infusion of nut galls (hot) and bring the two together.
One who has tried everything says that after an experience of fifteen years he has found nothing to equal the following: 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.
A cement made of very finely powdered oxide of lead (litharge) and concentrated glycerine, unites wood to iron with remarkable efficiency. The composition is insoluble in most acids, is unaffected by the action of moderate heat, sets rapidly, and acquires an extraordinary hardness.
The true marine glue is a combination of shellac and caoutchouc in proportions which vary according to the purposes for which the cement is to be used. Some is very hard, others quite soft. The degree of softness is also regulated by the proportion of benzole used for dissolving the caoutchouc. Marine glue is more easily purchased than made, but where a small quantity is needed the following recipe is said to give very good results: Dissolve one part of India-rubber in 12 parts of benzole, and to the solution add 20 parts of powdered shellac, beating the mixture cautiously over the fire. Apply with a brash.
The following recipe, taken from New Remedies, is said to yield a strong cement: 10 parts of caoutchouc or India-rubber are dissolved in 120 parts of benzine or petroleum (?) naphtha with the aid of a gentle heat. "When the solution is complete, which sometimes requires 10 to 14 days, 20 parts of asphalt are melted in an iron vessel, and the caoutchouc solution is poured in very slowly, in a fine stream, and under continued heating, until the mass has become homogeneous, and nearly all of the solvent has been driven off. It is then poured out and cast into greased tin moulds. It forms dark-brown or black cakes, which are very hard to break. This cement requires considerable heat to melt it; and to prevent it from being burnt, it is best to heat a capsule containing a piece of it first on a water-bath, until the cake softens and begins to be liquid. It is then carefully wiped dry, and heated over a naked flame, under constant stirring, up to about 300° F. The edges of the article to be mended should, if possible, also be heated to at least 212° F., so as to permit the cement to be applied at leisure and with care. The thinner the cement is applied, the better it binds.
Copal varnish, 15; drying oil, 5; turpentine, 3. Melt in a water-bath and add 10 parts slaked lime.
Gum arabic, 5; sugar candy, 2. White lead, enough to color.