This process consists in the employment of a pigment which is strongly attacked by acid. Clean the plate thoroughly with whiting and turpentine. Remove the whiting by rubbing the plate with bread; after removing which do not allow the hands to touch the plate. Crush a soft pastel into fine powder; mix with a strong solution of white sugar. Add a solution of ox-gall, about equal in quantity to half the sugar solution. The pigment must be so mixed as to work rather freely, and draw a thin line with ease and precision. With a small, fine-pointed sable-hair brush, make the drawing on the plate, depending mainly upon lines, as with a pen; when this is completed, be careful not to let anything touch the plate, as the pigment dries slowly. Dissolve some ordinary etching ground in ether; hold the plate with a pneumatic holder, and pour the solution upon the plate till it makes a pool reaching the sides of the plate; move the plate gently from side to side, then pour the superfluous solution back into the bottle. Heat the plate gently over a spirit lamp, holding it about 12 inches above the flame, and taking care to evaporate the ether gradually, and not to allow it to catch fire. The ground will become transparent.
Place the plate in a bath consisting of 100 grammes hydrochloric acid, 20 grammes chlorate of potash, 880 grammes water. The hydrochloric acid used-should not be of a deep yellow colour; should not gives off fumes, and, when mixed with water, should have but a slight odour.' Leave the plate in this bath 1/4 hour, then brush the surface of the plate very gently with a feather. This will remove the pigment and the ether varnish over it, leaving the lines exposed to the acid. The copper between them will be perfectly protected. Leave the plate in the bath until bitten-in to the required depth, stopping out when necessary. The finer portions of the work may either be finished with the dry point, or in point etching; in the latter case using a transparent ground. If any erasing is necessary, it must be done with a scraper. If the pigment does not take on the plate, the copper may be slightly roughened by a short immersion in a weak nitric bath. Let the ether ground remain a night on the copper before heating it, which must be very carefully done.