A blue pigment, obtained by adding chalk or whiting to a solution of copper in aquafortis. It is thus prepared. A quantity of whiting is put into a tub, and upon this the solution of copper is poured. The mixture is stirred every day for some hours together, until the liquor loses its colour. The liquor is then to be poured off, and more solution of copper is to be added; and the process thus continued, until the whiting has acquired the requisite depth of tint; when it may be first dried upon large pieces of chalk, and afterwards in the sun's rays. The inferior verditers are deficient of copper.