Valuable Secrets concerning Arts and Trades:
or Approved Directions, from the best Artists, for the Various Methods...
Printed by Thomas Hubbard,
Norwich, 1795Chap. III. Secrets for the composition of Varnishes, &c.
VIII. A black varnish.
1. Take gum-lac, four ounces: sandarak and black rosin, equal quantities, one ounce of each. Pulverise all separately, and keep them distinct, to proceed afterwards in their mixture according to the following directions. Dissolve the rosin over the fire in a sufficient quantity of spirit of wine; then add the sandarak to it. As soon as this is also dissolved, add the powder of gum-lac, and stir well till all is well melted together. Strain it, while warm, through a cloth. If any thing remain in the lin on afterwards, add same more spirit of wine to it to dissolve it as before; and strain it again after like the other. Such is the first preparation of this varnish.
2. The black colour is given to it by means of two drachms only of ivory black to every two ounces of it.
IX. How to make a good ivory-black for the above purpose.
Burn any quantity of ivory you please, in the fire, till it is black. Put it into powder on a stone of porphyry. Add some water to it, and make a paste, which you let dry. Then grind it again, as before, with spirit of wine.
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