1433. Another.—Blue verdigris, shaded with indigo, and heightened with white.
1434. To prevent Colors from Cracking.—Boil two ounces of the best and clearest glue, with one pint of clear water, and a half an ounce of alum, till dissolved. With this temper those colors intended for the sky.
1435. To make a Solution of Gum.—Dissolve an ounce of white gum arabic, and half an ounce of double refined sugar, in a quart of spring water; strain it through a piece of muslin, and bottle it to keep it free from dust.
1436. To keep Flies from the Work.—Having prepared the gum water for the colors, add a little coloquintida.
1437. To prepare Alum Water.—Take four ounces of alum, and a pint of spring water; boil it till the alum is thoroughly dissolved, and then filter it through blotting-paper.