DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20658#0328
314
COLOURING SUBSTANCES,
Take of the caput mortuum or residue found in the iron pots, after the distillation of aqua
fortis from nitre and vitriol, two parts, and of the colcothar remaining after the distillation or
calcination of martial vitriol, one part, break the larger pieces of these substances and put them
in tubs with a good quantity of water, and having let them stand for a day or-two, stirring them
frequently about, lade off as much water as can be got clear; then add fresh water, and continue
to do so until all the salts be washed out, and the water come off nearly insipid. The red powder
remaining in the vessel must then be washed over, and being freed from the water laid out to
dry. When this preparation is designed for the nicer purposes, it should be washed over again
in basins, the gross manner of lading it out of one tub into another not answering so well.
Venetian Red is a native red ochre, rather inclining to the scarlet than the crimson hue, and
is not very different from the common Indian red, but being not so pure is chiefly used by house-
painters in imitating mahogany, &c. and is easily prepared by mixing it with colcothar, and
grinding it properly with oil. In fitting it for more delicate works it ought to be very carefully
washed over.
Spanish Brozen is another earthy substance found in the state in which it is used, and is nearly
of the same colour with Venetian red but coarser: although it stands well yet it is only used for
common purposes. The only preparation required for this pigment is to free it well from stones
or dust and grind it with oil, to be fit for the colourman in preparing cloths for painters and
other coarse works.
Light Red or burnt Ochre is only the common yellow ochre made red hot in the fire, till the
colour change from yellow to red. This is an excellent colour both with water and oil, having
the property common to all the ochres of standing perfectly well.
Burnt terra di Sienna is made by calcining the raw earth of this name until it assumes a rich
red tint, very useful both in water and oil painting, as in both it stands well. Being in some
degree transparent it may be readily distinguished from other ochrous earths, and is thereby
difficult to counterfeit.
Red Chalk used for drawing on paper as with crayons, resembles light-red, and maj' be
employed in its place for several purposes, as it stands well either in oil or water.
OF BLACKS.
Lamp-black is the finest sort of what are called soot-blacks, and is the most used. It is com-
monly prepared during the process for making resins and turpentine. The impure resinous juice
collected from incisions made in pine an-d fir-trees, is boiled down with a little water, and whilst
hot strained through a bag,- the dregs and pieces of bark left in the strainer are then burnt in a
slow oven, from which the smoke is conveyed through a long passage into a square chamber,
having an opening on the top, on which is a large sack of thin woollen cloth. The soot, or
lamp-black as it is called, concretes partly in the chamber, from whence it is swept out once in
two or three days, and partly in the sack, which is now and then gently struck, both to shake
down the soot already collected, and to clear the interstices between the threads, so as to produce
a sufficient draught of air through the sack. Lamp-black is prepared in this manner in Sweden,
and also in the turpentine houses in England, from the dregs and refuse of the resinous matters
there manufactured.
Another
COLOURING SUBSTANCES,
Take of the caput mortuum or residue found in the iron pots, after the distillation of aqua
fortis from nitre and vitriol, two parts, and of the colcothar remaining after the distillation or
calcination of martial vitriol, one part, break the larger pieces of these substances and put them
in tubs with a good quantity of water, and having let them stand for a day or-two, stirring them
frequently about, lade off as much water as can be got clear; then add fresh water, and continue
to do so until all the salts be washed out, and the water come off nearly insipid. The red powder
remaining in the vessel must then be washed over, and being freed from the water laid out to
dry. When this preparation is designed for the nicer purposes, it should be washed over again
in basins, the gross manner of lading it out of one tub into another not answering so well.
Venetian Red is a native red ochre, rather inclining to the scarlet than the crimson hue, and
is not very different from the common Indian red, but being not so pure is chiefly used by house-
painters in imitating mahogany, &c. and is easily prepared by mixing it with colcothar, and
grinding it properly with oil. In fitting it for more delicate works it ought to be very carefully
washed over.
Spanish Brozen is another earthy substance found in the state in which it is used, and is nearly
of the same colour with Venetian red but coarser: although it stands well yet it is only used for
common purposes. The only preparation required for this pigment is to free it well from stones
or dust and grind it with oil, to be fit for the colourman in preparing cloths for painters and
other coarse works.
Light Red or burnt Ochre is only the common yellow ochre made red hot in the fire, till the
colour change from yellow to red. This is an excellent colour both with water and oil, having
the property common to all the ochres of standing perfectly well.
Burnt terra di Sienna is made by calcining the raw earth of this name until it assumes a rich
red tint, very useful both in water and oil painting, as in both it stands well. Being in some
degree transparent it may be readily distinguished from other ochrous earths, and is thereby
difficult to counterfeit.
Red Chalk used for drawing on paper as with crayons, resembles light-red, and maj' be
employed in its place for several purposes, as it stands well either in oil or water.
OF BLACKS.
Lamp-black is the finest sort of what are called soot-blacks, and is the most used. It is com-
monly prepared during the process for making resins and turpentine. The impure resinous juice
collected from incisions made in pine an-d fir-trees, is boiled down with a little water, and whilst
hot strained through a bag,- the dregs and pieces of bark left in the strainer are then burnt in a
slow oven, from which the smoke is conveyed through a long passage into a square chamber,
having an opening on the top, on which is a large sack of thin woollen cloth. The soot, or
lamp-black as it is called, concretes partly in the chamber, from whence it is swept out once in
two or three days, and partly in the sack, which is now and then gently struck, both to shake
down the soot already collected, and to clear the interstices between the threads, so as to produce
a sufficient draught of air through the sack. Lamp-black is prepared in this manner in Sweden,
and also in the turpentine houses in England, from the dregs and refuse of the resinous matters
there manufactured.
Another