THe present art of gilding upon glass is an improvement on the method in fashion years ago. It is chiefly used for decorating the borders of prints in executing show glasses, and inscriptions for various purposes, also for ornamental decorations in a variety of elegant forms, upon different colored grounds; but as black is the most general one in demand, shall first treat on that, there being two ways of performing it.
Procure some fine isinglass. You will find white and transparent is the best, otherwise it will be unfit for this purpose. Dissolve it in very clean water, and strain through linen cloth. Put a piece the size of a pea into a tea cup of luke warm water, and let it remain until dissolved. Make the glass you wish to have gilded quite clean, and free it of any dust or grease, get some leaf gold, put it on a gilding cushion, and cut into pieces according to the breadth you wish to have your work gilt. Go over the parts to be gilt with a hair pencil, dipped in the thin isinglass water, and while moist lay on the leaf gold, piece by piece, until the parts are covered. The leaf will instantly adhere to the glass. Then place it near the lire, in a slanting position, until it dries, which will be in a few minutes.
While it is slightly warm, take a piece of cotton or wool and rub the gold to the glass, until you find the superfluous pieces of leaf gold gone, and likewise the back of the part gilt receives a kind of polish. Proceed to lay on a second coat of gold, in the same manner as the first, drying it as before, and polishing it, and so a third coat, which will be sufficient.
Then take the size of the print or drawing which is to be framed, and laying it on the gilt part of the glass, mark where the edges come to, with a hair pencil and some dark color, after which, being provided with a long ruler, and a pointed piece of ivory, draw two parallel lines out of your gold, and with a mahogany or deal stick, carefully pointed, work away the superfluous part, leaving the gold fillet which is to encompass the picture sharp and neat. If you wish to ornament it by any other lines, to appear black in the center, lay on your ruler, and with the ivory point scribe them, and then varnish, having some black Japan, to which a little lampblack has been added, to deepen the color. Paint it all over the gilt part of the glass, and the space between it and the edge, then set it to dry, which takes a few hours. When you are to lay out the breadth of the black line that is to be inside your gilding, scribe it with a sharp point, and cut away the waste black with a graver, or some sharp instrument.
To cut figures, or any kind of ornament out of your gold, after the glass is gilt, have a drawing of the design on paper, at the back of which rub some powdered red chalk, and the smallest quantity of fresh, butter ; lay the paper on the gold, and with a bluntish ivory point go over the lines of the drawing, and they will be nicely transferred on the gold, when you can with an ivory point trace them out of the gold, and shade them agreeable to your fancy, or from the drawing you have by you. You may, by mixing any other color you choose with white copal varnish, vary your ground as you think proper.
The most important secret in glass gilding is the following method: In an instant after your glass is blacked, taking away the parts where the gold is to appear, and the remainder of the black to stand fast, by which means the black gilding work is done in one-half the time, and with half the gold leaf. The process is simple, and is performed as follows: Obtain the very best black Japan carriage varnish, to which add a very small portion of burned lampblack, very finely ground in spirits of turpentine ; then with a large flat varnish brush give the glass one even thin coat, holding it between you and the light, and observing that it does not appear a thick dead black, but exhibits a degree of transparency not so much so as to prevent its appearing a good black at the right side of the glass. After this, have the letters and ornaments drawn on paper, as before mentioned, and trace it in the same manner on the black varnish when it is perfectly dry. The drawing will be thus very finely transferred to the black. Then take a needle pointed bodkin and finely mark the outlines of what black is to come out through the varnish , take some thick brown paper, dip it in water, and squeeze it gently, spread it over the parts of the varnish you want to detach from the glass, and in a few minutes, by raising one edge of the black, it will instantly peel away clean from the glass. When all the black you want is taken out, lay the glass to the fire, and the remaining part of the varnish will instantly become as hard as ever, and ready to have the gold put on.