Chapter IX

Of Staining and Aciding--Yellow Stain--Aciding--Caution required in
Use--Remedy for Burning--Uses of Aciding--Other Resources of
Stained-Glass Work.

Yellow stain, or silver stain as some call it, is made in various ways from silver--chloride, sulphate, and nitrate, I understand, are all used. The stain is laid on exactly like the pigment, but at the back of the glass. It does not work very smoothly, and some painters like to mix it with Venice turpentine instead of water to get rid of this defect; whichever you use, keep a separate set of tools and a separate palette for it, and always keep them clean and the stain fresh mixed. Also you should not fire it with so strong a heat, and therefore, of course, you should never fire pigment and stain in the same batch in the kiln; otherwise the stain will probably go much hotter in colour than you wish, or will get muddy, or will "metal" as painters call it--that is, get a horny, burnt-sienna look instead of a clear yellow.

_How to Etch the Flash off a Flashed Glass with Acid._--There is only one more process, having to do with painting, which I shall describe, and that is "aciding." By this process you can etch the flash off the flashed glasses where you like. The process is the same as etching--you "stop-out" the parts that you wish to remain, just as in etching; but instead of putting the stopping material over the whole bit of glass and then scratching it off, as you do in copper-plate etching, it is better for the most part to paint the stopping on where you want it, and this is conveniently done with Brunswick black, thinned down with turpentine; if you add a little red lead to it, it does no harm. You then treat it to a bath of fluoric acid diluted with water and placed in a leaden pan; or, if it is only a touch you want, you can get it off with a mop of cotton-wool on a stick, dipped in the undiluted acid; but be careful of the fumes, for they are very acrid and disagreeable to the eyes and nose; take care also not to get the acid on your finger-ends or nails, especially into cuts or sore places. For protection, india-rubber finger-stalls for finger and thumb are very good, and you can get these at any shop where photographic materials are sold. If you do get any of the acid on to your hands or into a cut, wash them with diluted carbonate of soda or diluted ammonia. The acid must be kept in a gutta-percha bottle.

When the aciding is done, as far as you want it, the glass must be thoroughly rinsed in several waters; do not leave any acid remaining, or it will continue to act upon the glass. You must also be careful not to use this process in the neighbourhood of any painted work, or, in short, in the neighbourhood of any glass that is of consequence, the fumes from the acid acting very strongly and very rapidly. This process, of course, may be used in many ways: you can, by it, acid out a diaper pattern, red upon white, white upon red; and blue may be treated in the same fashion; the white lights upon steel armour, for instance, may be obtained in this way with very telling effect, getting indeed the beautiful combination of steely blue with warm brown which we admire so in Burne-Jones cartoons; for the brown of the pigment will not show warm on the blue, but will do so directly it passes on to the white of the acided parts. This is the last process I need describe; the many little special refinements to be got by playing games with the lead lines; by thickening and thinning them; by _doubling_ glass, to get depth and intensity, or to blend new tints;--these and such like are the things that any artist _who does his own work and practises his own craft_ can find out, and ought to find out, and is bound to find out, for himself--they are the legitimate reward of the hand and heart labour spent, as a craftsman spends them, upon the material. Suffice it to say that in spite of the great skill which has been employed upon stained-glass, ancient and modern, and employed in enormous amount; and in spite of the great and beautiful results achieved; we may yet look upon stained-glass as an art in which there are still new provinces to explore--walking upon the old paths, guided by the old landmarks, but gathering new flowers by the way.

We must now, then, turn our attention to the mechanical processes by which the stained-glass window is finished off.