Take crude Naples-yellow, (the heaviest for bulk is the best) and break it into small pieces with the mallet upon the grinding stone, put it in a clean earthen vessel, and pour over it a quantity of new milk, sufficient to cover it three or four inches over, stirring it well for some time with a wooden spatula or stick; then let all together stand undisturbed for five or six days, and the milk will become thick and sour, and master by its acidity the noxious saline principles of the colour; having stood the abovementioned time, take off the creamy part from the top of the milk, and pour warm water upon it, and let the vessel overflow till you perceive the water to come off as clear as when poured on, and the colour will be purified and fit for use.
Light-oker, a precipitated, feruginous earth, answers in encaustic all the purposes it does in oil.
Brown-oker, a precipitated feruginous earth too, only it partakes a little of a vitrioline principle, which the light-oker does not. In encaustic this colour answers all the purposes it does in oil.
Yellow orpiment, or king’s-yellow. The principal constituent particles of this colour are, sulphur and arsenic, which latter prevails and makes great havock among the other colours when used in oil; it cannot play the same tricks fixed with wax; wax being a closer and unvariable body, confines its arsenical principle. Oil once dry ceases to be oil, and can confine them no longer.
Red-orpiment, so called to distinguish it from the other, is properly not red, but of a rich orange colour, and is a compound of arsenic and sulphur too; but here sulphur prevails, which is the reason of its standing its ground better and doing less harm in oil than the other.
In encaustic it is of universal use, throughout a whole picture to give warmth to lights and shades; in landscapes it may be used from the horizon down to the fore ground, to good purpose; for shades in flesh it is admirable, it gives a clear, soft and transparent strength; in the verdure of landscapes it answers all the ends for brown-pink, when mixed with a little bone black.
This colour is very conspicuous in all the warmer landscapes of Claude Lorraine; Mr. Vernet a famous French painter uses it very much.
PINKS.
Light-pink, and brown-pink.
These two colours ought rather not be used, as they both proceed from the same vegetable principle, viz. the juice or extract got by decoction from French berries by the help of acid salts; consequently incapable to sympathise with or admit wax into their pores[12]; the wax can take hold of them only superficially, which makes them appear dry and gritty upon the picture, and will easily come off by rubbing them with one’s finger. Those artists who cannot do without them, will do well to grind them, the light-pink with a little light-oker, and brown-pink with a little brown-oker, and they will keep a little better; but red-orpiment and a little bone black, making as fine a pink as that properly so called, it will be best to use the latter.