Scientific American 35, 20.5.1848
The surface to which the print is to be transferred must be covered with copal varnish; afterwards receive a thin coat of mixture of copal varnish and old linseed oil; or of an article sold by the druggists under the name of transfer varnish, and which consists of a mixture of copal varnish, and fir-balsam. When this is partly dry, but yet remains adhesive, the print is first dipped in water and allowed to remain a few minutes in the open air, to allow part of the moisture to evaporate. It is then spread smoothly on the varnished surface, with the smooth surface down, and gradually pressed down on the varnish with cotton, or other soft substance. When the varnish has become nearly dry, the print may be pressed down a little harder; and when the varnish has become thoroughly dry, the paper is wet with a sponge, and rubbed carefully with the fingers till the paper peals off in small rolls, leaving all the lines and shades of the print adhering to the varnish. The process of transferring prints to glass is the same, with the exception of the primary varnishing.