1. Technology of dyeing
While dyeing is usually carried out in such a way as to obtain uniform tints, in some cases, like that of horn, differences in colouring are required.
To obtain a range of bright colours, the fat must first be removed from the horn by placing the horn in a bath of warm water to which 10 g of washing soda has been added. The horn may then be coloured by synthetic dyes, in the same way as for dyeing bone, but in a more concentrated and cooler solution.
A jet-black colour can be obtained by soaking the horn for several hours in the following solution:
The salts of mercury fixed in the horn are then sulphurated by immersion in the following solution:
The horn must finally be rinsed and left to dry.
To give the horn a white colouring, the following must be homogeneously blended:
The horn is left to soak in this solution for about 20 minutes. It penetrates into the keratin impregnated with lead which sulphurises on contact with the sulphur. The horn should not be left in longer because it will become brittle and the surface will take on a powdery appearance. Objects made of horn are wiped after being removed from the bath. They are then put immediately into an acid bath containing water to which 250 g of hydrochloric acid have been added per litre. When the desired colour has been obtained, the objects should be dried in bran.
The tortoiseshell type of mottling is obtained by applying the following mixture to certain areas:
The lead combines with the sulphur in the horn to form a black pigment.
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