TO COUNTERFEIT TORTOISE SHELL VERY FINELY.
In order to do this well, your foundation or ground-work must be perfectly smooth and white, or nearly so, you then gild it with silver leaf with slow size, so as to have it perfectly smooth with no ragged edges, cleaning the loose leaf off. Then grind cologne earth very fine, and mix it with gum water, common size; and with this, you having added more gum water than it was ground with, spot or cloud the ground-work, having a fine shell to imitate; and when this is done, you will perceive several reds, lighter and darker, appear on the edges of the black, and many times lie in streaks on the transparent part of the shell. To imitate this finely, grind dragon’s blood with gum water, and with a fine pencil draw those warm reds, flushing it in about the dark places more thickly, but fainter and fainter and thinner, with less color towards the lighter parts, so sweetening it that it may in a manner lose the red, being sunk in the silver or more transparent parts. When it is dry, give it a coat of varnish, let it stand for a few days, then rub it down with pumice stone and water. Then grind gamboge very fine, and mix with varnish, giving of this as many coats as will cause the silver to have a golden color, then finish with a clean coat of varnish.