Valuable Secrets concerning Arts and Trades:
or Approved Directions, from the best Artists, for the Various Methods...
Printed by Thomas Hubbard,
Norwich, 1795Chap. V. Secrets concerning colours & painting.
§ VIII. Preparations of colours of all sorts for oil, water, and crayons.
1. Take one pound of Alicant kali or Bril-ash, pulverised, which put in a kettle with four quarts of spring water. Boil the whole for the space of a quarter of an hour, keeping stirring all the while with a stick, then take it off from the fire; and let it cool so as to be able to keep your finger in it without scalding. When it is in that state, throw it in a jelly bag, made of cloth, to filter it, and render it perfectly clear. Put it, next, in a new glased pipkin, with one ounce of finely pulverised cochineal, previously diluted by degrees with some of the same lye. Set it a-boiling for half a quarter of an, hour, and never cease to stir with a stick all the while it is on the fire. - You may, if you chuse, add one drachm of terra merita in fine powder, at the same time with that of the cochineal; it will render your lake the reder. - When the whole shall have boiled the prescribed time of half a quarter of an hour, take it off the fire, and let the tincture cool, in order to pass it through a cloth, or the above-mentioned jelly-bag. Set a large stone pan under the bag to receive the tincture which shall filter; and, when all is well drained, take the bag, turn it to throw off all the dregs, and warn it well, inside and outside, in clear water, and wring it quite dry.
2. Now hang again this same bag at two feet distance, or thereabouts, above the pan wherein the tincture did run, and now is. Dissolve, in about two quarts of warm spring water six ounces of Roman alum well pounded, that it may, more readily melt. When this dissolution is no more than lukewarm, have somebody to pour it for you in the above jelly-bag, while you stir with a stick what runs from it into your tincture, and do so till the whole is passed through, and the tincture froths no more. - Then wring well your bag again, to express all the alum's dissolution from it into your tincture, and wash it again afterwards in clear water, as before.
3. Have another stone pan like the first, hang your bag again over it, and pour all your tincture in it. If it run clear like water, you may then let it go so; if not, put it again in the bag over the ether, and continue so to do till it absolutely does run clear. If, however, after having repeated this three or four times, it should continue to run tinged, dissolve two or three ounces more of pulverised Roman alum in about two quarts of that very tinged water, then stir and mix it well in the whole quantity of tincture, then pour it again in the bag where the lake is, repouring again and again what shall run first from it, till it runs quite clear, and does not even stain the paper.
4. Then let well drain the lake which is in the bag; and, with a box-spoon take it, and spread it on pieces of cloth, laid on plaistered stones, and let it dry in the shade where there is no dust, or where, at least, you may preserve it from any.
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