GLASS.— Painting.

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and of bismuth, the flux is usually composed of thefollowing ingredients:—

Parts.

Quartz in powder,. 100

Oxide of lead,. 125

Oxide of bismuth,. 50

But if these oxides exert an injurious action on thecolouring matter, and tend to change its shade, thesubjoined composition is used:—

Parts.

Quartz in powder,. 100

Fused borax,. 75

Nitrate of potash. 12-5

Carbonate of lime, free from iron,. 12*5

To either of these mixtures or fluxes the propercolouring matter is added, and the composition soformed is introduced into a crucible, and melted intoa coloured glass. The latter is then reduced to afine powder, mixed, as has been stated, with oil ofturpentine, and used as a common pigment forpainting on the less fusible glass. In this operationa cartoon, or drawing upon paper, is placed belowthe glass, and the colours are applied on the cor-responding lines. In preparing painted sheets orpanes of glass, brown or black outlines are generallytraced on the one side of the sheet, whilst the coloursare laid on the other side; hut in painting vesselsor other articles, this is not the practice.

One great difficulty of the glass-painter consistsin this, that the colours which he lays on have notthe same appearance as they are intended to assumein the finished work. When the same figure orpattern is to be repeated many times, it is, in somecases, printed on the glass with a gentle pressurefrom an engraved metallic plate, or wooden block,boiled oil being used as the vehicle for the colouringoxide. The pane, having been prepared either bypainting or printing, is exposed in an oven or muffleto a temperature sufficient to fuse the vitreous fluxand dissolve the colouring material.

Professor Bakff describes the method pursued inthe manufacture of stained glass windows as fol-lows :—After a design has been drawn, in which theeffect of the window as a whole can he carefullyconsidered, cartoons of the figures and ornamentsare made of the exact size of the intended painting,the lines being extremely clean, precise, and welldrawn, because it is from these that the workman,who is not usually himself an artist, has to conveyon the glass the feeling of the artist.

The cartoon when completed is laid down inpieces for convenience sake on a table, and fastenedwith small nails. The glass-cutter then selects thevarious coloured glasses which are required to beinserted in their proper places, so as to carry out thedesign. For instance, a piece of white or yellowtinted glass is cut to the shape of the face. If thefigure be a small one the hair also is included inthis ; and probably in the figure of a saint thenimbus which surrounds the head may be included;while in larger figures the face is of glass of onetint, the hair of another, and the nimbus of one ormore tints, different from these.

The outlines of the figure are painted with asubstance called “ tracing brown,” made by mixingsome oxide of iron with a flux, heating them togetherin a crucible, and grinding the product to a finepowder, which is mixed with the articles adapted tothe particular use to which it is to be applied.

Different fluxes are employed by different glasspainters: some contain borax, because these fluxesfuse more easily. These are, however, liable to be-come hydrated, and in this condition often cause thepainting to peel away. Harder fluxes are the best,though they require more heat. Lead fluxes aresufficiently fusible for all ordinary purposes, and arenot liable to the objection of those containing borax.

Suppose it is desired to paint the outlines of aface, the glass is cut to the shape denoted in thecartoon; it is then laid upon the cartoon, and thepainter seeing the lines through the glass, tracesthem with his brown paint. lie generally uses gumwater a3 his vehicle, and puts on the shading alsowith the gum mixture, though sometimes it is foundnecessary to use a substance which is not affected bymoisture, as, for instance, tar oil. When the face isfinished it is removed, and another portion of thefigure proceeded with; and so on till by a repetitionof this process the figure is completed, when all theparts are put on the cartoon, in order to see that thewhole is harmoniously treated.

In shading, a glass easel is used, on which thefigure is put together, and the parts made to adhereby wax, so that the artist is able while painting toform an idea by transmitted light of the effect whichwill be produced when the picture is finished.

When all the glass is painted it is fired in a muffle,upon the proper construction of which a great dealdepends. It is usually made of iron, and should notbe more than 15 inches from its bottom to the top.It is never well to have it longer than about 2 feetwide by 2 feet 6 inches deep. The top of the muffleis usually slightly arched from side to side, and it isplaced in the furnace on a tolerably thick stone floor,so that the bottom may not get too hot. The fire,which is lighted below, is allowed to play up its sidesand over its top, the flue being so placed as to drawthe flames in that direction. The muffle has ridgesin its sides to receive iron plates, and there is gener-ally about an inch, or rather less, between the topof one plate and the bottom of another. The platesare covered over with perfectly dry powdered chalkor whiting, and the pieces of glass are laid upon themwith their painted sides uppermost. The muffle hastwo doors, between which is a conical tube to enablethe workman to look in from time to time to seethat the glass is not overheated. When the firing iscompleted, the muffle is allowed to cool slowly, inorder to anneal the glass.

When the pieces of glass are perfectly cold theyare united by peculiarly shaped strips of lead. Thelead has a thick core, and at right angles to thebottom and top of this are thin plates called theleaves. The core is drilled with little ridges so as toenable the workmen to bend the lead about withfacility. The joints of the lead are soldered, and