Domestic Encyclopædia (1802)/Print

PRINT, an impression taken from a copper-plate.

As prints are more durable than paintings, and form a valuable part of the furniture of almost every house, we shall subjoin a method of cleaning and bleaching them, in case they become stained by accident, or otherwise soiled. It was invented by Signior Fabbroni, an Italian chemist, who published it in Brugnatelli's Annali di Chimica.—He directs a strong glass bottle to be half-filled with a mixture of one-fourth part of red lead, and three-fourths of spirit of salt, and to be closely secured by a glass stopper. The vessel is then to stand in a cool shady place, till a certain degree of heat, which is spontaneously produced, indicates the forming of new combinations. The minium loses a considerable portion of its oxygen, which unites with the liquor, and communicates to it a rich gold colour, together with the smell of oxygenated muriatic-acid (bleaching liquor); and a small quantity of lead is held in solution, which does not, however, lessen its effects.

In order to employ the liquid, thus prepared, a border of white wax should first be formed, about two inches in height, upon a large pane of glass: on this, the prints must be laid, in a ley made either of fresh urine, or of water mixed with a little ox-gall, for the space of three or four days; at the expiration of which time the liquor must be supplied with warm water, that ought to be changed every third or fourth hour, till it is poured off perfectly clear. Should any resinous matter remain on the prints, they must be moistened with a little alkohol.

The moisture must next be drained; and the print, being again placed on the plate of glass, ought to be covered with the oxygenated muriatic-acid liquor. Another pane is then to be placed on the lower one, to prevent any dangerous consequences arising from the pernicious vapour of the acid. In the course of one or two hours, the most discoloured prints will be restored to their original beauty. Lastly, after pouring off the acids, the prints must be washed two or three times in pure water, and dried in the sun.