BACK-Painting, the method of painting mezzotints, pasted on glass, with oil-colours.
The art consists chiefly in laying the print upon a piece of crown-glass, of such a size as fits the print.
In order to do this, take your print, and lay it in clean water for two days and two nights, if the print be on very strong, close, and hard gummed paper; but if upon an open, soft, spongy paper, two hours will sometimes suffice, or more, according as the paper is.
The paper or picture having been sufficiently soaked, take it out and lay it upon two sheets of paper, and cover it with two more; and let it lie there a little to suck out the moisture.
In the mean time, take the glass the picture is to be
put upon, and set it near the fire to warm; take Strasburg turpentine, warm it over the fire till it is grown fluid, then with a hog's-hair brush spread the turpentine very smoothly and evenly on the glass.
When this has been done, take the mezzotinto print from between the papers, and lay it upon the glass; beginning first at one end, rubbing it down gently as you go on, till it lie close, and there be no wind bladders between.
Then, with your fingers, rub or roll off the paper from the back-side of the print, till it looks black, i. e. till you can see nothing but the print, like a thin film, left upon the glass, and set it by to dry.
When it is dry, varnish it over with some white transparent varnish, that the print may be seen through it; and then it is fit for painting.
The utmost care will be necessary in rubbing or rolling the paper of the print, so as not to tear it, especially in the light parts.
You may, instead of soaking your prints two days and two nights, roll them up and boil them for about two hours, more or less, according to the quality of the paper, in water; and that will render it as fit for rubbing, rolling, or peeling, as the other way.
This being done, and your oil-colours prepared, ground very fine, and tempered up very stiff, lay on the back-side of the transparent prints such colours as each particular part requires; letting the master-lines of the print still guide your pencil, and so each particular colour will lie fair to the eye on the other side of the glass, and look almost as well as a painted piece, if it be done neatly.
The shadows of the print are generally sufficient for the shadow of every colour; but if you have a mind to give a shadow by your pencil, then let the shadows be laid on first, and the other colours afterward.
In laying on colours in this kind of back-painting, you need not be curious as to the laying them on smooth. This is not at all requisite here, where the chief aim is only to have the colours appear well on the fore side of the print; and therefore the only care to be used in this work, is to lay the colours on thick enough, that its body may strike the colour of it plainly through the glass.