ss 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 thin