ART. II.
Of the colours and their preparation.
All colours used in oil painting are fit for this manner, and no others. There are a few that ought to be omitted; for reason see the list of colours.
Grind all your colours very fine with simple water, allot to every particular colour a distinct vessel, such as gallipots, pans, &c. From your colours so ground, compose all the different principal tints, asthe nature of your intended work shall require.
But, as most of the colours acquire a deeper hue when moistened, and some deeper still when fixed with wax, it will be necessary, to prevent perplexity in the execution, to have a guide for retouching, either when the picture is finished and dry, before the operation of the fire, or after it is fixed; for this purpose you may, before you go to work, use the following expedient.
Take two slips of cloth about a foot long, and three orfour inches wide, wax them as before mentioned, then upon the one slip paint of every one of your entire colours6about an inch high over the whole width of the cloth, and with your tints already composed do the same upon the other piece of cloth, according to their order and degradation;7mark every tint with a number, such as 1, 2, 3, &c. write down upon a paper every number, and what it is composed of. This done and your colours so applied dry, cut your cloth across all the tints fromtop to bottom in two equal parts; bring one half of each near the fire, and by melting the wax fix them, the other two halves you keep as they are unfixed.
By rejoining and comparing them together, you may judge what strength every tint will acquire, and by their reciprocal references you will be enabled to alter or imitate, deepen or heighten with certainty, any tint, either before or after the colours are fixed.
In painting be not sparing; the greater body of colours you employ, the better and brighteryour work will appear; you may give greater freedom to your pencil, blend and sweeten your colours better than in any other way of painting.