Up: Glassmaking
Reminiscences
109 of 123
|
|
| |
water, and pour it steadily into the solution of tin as above prepared,
stirring all the while. Let it settle twenty-four to thirty hours;
pour off the water, leave the settlings, pour in two thirds of a quart
of water. Stir it thoroughly; let it settle thirty hours; pour off as
before, and filter the precipitate through filtering paper. The result
is the purple of
Crassus. The ounce of gold thus prepared must be well
incorporated with the following batch: say thirty-two pounds of fine
silex, thirty-six pounds oxide of lead, sixteen pounds refined nitre;
melt the same in a clean pot, one little used, and smooth inside; when
filled in, put the stopper to the pot loose, leaving it slightly open;
leave it five or six hours, or time to settle, then a back stopper can
be put up. In the usual time it will be ready to be worked out in solid,
egg-shaped balls, and exposed to the air to be partially cooled; they are
then to be placed in the leer under a strong fire, which will in two or
three hours turn them to a red color; then the pans may be drawn slowly
to anneal the balls.
It is well known to mixers that colored glass
is derived from metal oxides. To obtain the proper color depends on the
purity and strength of the metallic oxides. The following receipts have
with success been used:--
ALABASTER.
| To |
500 |
lbs. |
of batch add |
|
30 |
" |
phosphate of soda, |
|
10 |
" |
allumine,-- i.e. calcined alum, |
|
3 |
" |
calcined magnesia. |
BLACK.
| To |
1400 |
lbs. |
of batch add |
|
180 |
" |
manganese, |
|
100 |
" |
calcined iron scales, made fine, |
|
20 |
" |
powdered charcoal, |
|
10 |
" |
arsenic. |
|
|