1869.] Stained Glass frdm the Old Authorities. 659 emplo3 r ed with caution, according to the work which is to be executed ; and care must be taken not to efface the outlines ; or the colors may be conveniently ap- plied on the other side of the glass. Yellow is, most frequently, made in the furnace; but, in using, it must alwa3 T s be laid on the back of the glass very even, more or less charged, accord- ing to desire, and never near blue ; be- cause, in being melted and re-heated in the fire, these two colors would only make one, which would be green. It is for this reason necessary, as has already been said, to lay on the 3'ellow, on that side, where there are no other colors ; for it sinks through the whole thickness of the glass. This other colors do not ; for these last, having more body, do not penetrate so far, and some of them even remain on the surface. When the colors are to be baked, and the glass put in the fire, after being painted, a small square furnace of brick is to be made, which each way should not be more than about eighteen (18) inches, that is to say, however, accord- ing to the quantity of work which has been prepared. At the lowest part, and six inches from the bottom, an opening is to be made, to put in and stir the fire. Above this opening, two or three square bars of iron are to be placed, which will cross the furnace, and divide it into two. Over these bars, and to the right of the door below, a small opening is to be left of about the thickness of two fingers in height and breadth, to let the trial-pieces pass through, while the work is baking. The furnace thus prepared, an iron pan, of the form of the lurnace, must be procured, of such a size as that, beino- laid on the bars of iron, it shall want about three full finger's breadth or more of touching the walls of the furnace ; for which reason it ought to be square, and it should be of good earth, well baked. Its bottom should be about the breadth of two fingers in thickness, and its height, at its sides, about half a foot. After this, a quantity of plaster, in powder, well sifted, and three times baked in a potter's furnace or a tile-kiln, must be provided, or rather of quick- lime well separated or sifted. Some persons use cinders well burnt, but they are not so well adapted for fitting the pieces intended to be baked. The pan being placed on the bars, in the middle of the furnace, a portion of the plaster in powder, or of the lime, must be spread there, about half a finger's breadth in depth, as equally as possible, and, above, some pieces of old broken glass are to be placed, and then some powder, then some old glass, and then some powder, so that it may have three beds of plaster or lime, and two of old glass, which is called stratum upon stratum. On the third bed of plaster the pieces which have been painted should begin to be spread. They are to be laid in beds, so that there may be half a finger's breadth of powdered plaster, or lime, very evenly spread be- tween each piece of glass; and the ranges in this order be placed one above another, continually, until the pan is full, if the number of pieces to be baked is sufficient to fill it. After this, the last bed is to be covered with some of the powder, and it must be remembered that the pan should have a hole in front, to answer to that of the furnace, above the door through which the fire is put in order that the pieces of glass, with which the, trials are made, passing straight from one to the other, may enter into the pan, and there bake the same as the rest. All things thus disposed, some bars of iron are to be placed, which may rest on the walls of the furnace ; and the pan is to be covered with a large tile, made on purpose, or with several others. They are to be ranged and luted as closely as possible, with some soft earth or mould, so there may be no aperture, except at the four corners of the furnace, where one ought to be left, of about two inches in diameter, in each corner.
