itt 
ETCHING, 
ceive the ink in proportion as ag Aol been corroded, _ Etching, 
If the heat be continued too 
, and will be apt to 
pi 
is to be wrapped in a piece of 
, and laid on the warmed ¥ i di- 
sbicigngonmeien renin, shoxving ¢ ei 
Hj 
E 
F 
i 
HEN 
itt 
i 
: 
: 
zp 
i 
E 
o 
213 
while the polished are left free, per being laid 
upon this, and pressure applied, will uve an agreeable 
impression. 
Messrs Brown and Mawe of Derby, and in the Etching 
Strand, London, have latel 
the very elegant articles w 
coloured 
tique ornaments are beautifully enriched with figures 
etched upon them by acids. If sulphuric ‘acid of 
tolerable be laid upon polished gypsum, it 
gives to the part a dead white, which forms a good con- 
trast with the polished For marbles or any car- 
introd: 
etching u 
ich 
does not merely deaden the agp but forms a greyish 
ground, which is an agreeable contrast to the black po- 
oF 
i 
employed to ornament glass wi 
corrosion of glass by the fluoric acid gives 
of ground glass, so that when the fi- 
upon glass are defended from the acid 
bstance, the d becomes opaque, form- 
contrast to the transparent part. The lat- 
ly painted representing figures or flowers, 
manner of painting transparencies. The com- 
ing ground is generally used ‘to cover the 
same manner as the copper-plates are first 
taking the same pains to sp it uniformly. 
, the figures, but more commonly the —<_ 
formed by needles of different 
; and a flat pointed tool when greater surfaces are 
be removed. As soon as those parts intended to be 
corroded are cut out, they are surrounded with soft 
wax, as directed to be placed round the margin of the 
oe ora Somer berwaaned sorrmck aie The 
eae ee 1. By the li- 
b caytie 2. By pounded fluor spar; and, 3. By 
acid gas, or what is more ly called the su- 
t of silex. The liquid acid 1s obtained by distil- 
ing the gas from fluat of lime and sulphuric acid, from 
a leaden retort into a receiver of the same metal, sur- 
rounded with ice, and containing a little water. The 
liquid obtained is to be employed on the in the 
same manner as the dilute nitric acid in etching copper- 
plates. The second method is the most simple, and is on 
that account generally i It consists in first redu- 
cing the fluat of lime, commonly called fluor spar, and 
Blue John, to powder. When the sides of the outlined 
ii 
f 
: 
‘it 
ai 
he 
" 
the acid as about three to one by weight. It must be 
placed in a warm situation, but not so hot as to melt the 
wax or varnish. The sulphuric acid soon begins to li« 
berate the fluoric acid, which in its nascent state core 
The gas are tiys ta WL ea the si- 
along with it in the form of superfluat 
= ee ees 
very pure, that is, free from silex. If the latter be 
oe oni RNa A Cn lee 
of getting the silex from 
form of various lc and 
les and gypsum. Vases and other an- 8YP°0™ 
plates do not answer for Dw Etching 
good upon glass, 
