s are brought from the mines there, and treated in
Rome by public contractors. These manufactories are between the temples
of Flora and Quirinus.

5. Cinnabar is adulterated by mixing lime with it. Hence, one will have
to proceed as follows, if one wishes to prove that it is unadulterated.
Take an iron plate, put the cinnabar upon it, and lay it on the fire
until the plate gets red hot. When the glowing heat makes the colour
change and turn black, remove the plate from the fire, and if the
cinnabar when cooled returns to its former colour, it will be proved to
be unadulterated; but if it keeps the black colour, it will show that it
has been adulterated.

6. I have now said all that I could think of about cinnabar. Malachite
green is brought from Macedonia, and is dug up in the neighbourhood of
copper mines. The names Armenian blue and India ink show in what places
these substances are found.

CHAPTER X

ARTIFICIAL COLOURS. BLACK

1. I shall now pass to those substances which by artificial treatment
are made to change their composition, and to take on the properties of
colours; and first I shall treat of black, the use of which is
indispensable in many works, in order that the fixed technical methods
for the preparation of that compound may be known.

2. A place is built like a Laconicum, and nicely finished in marble,
smoothly polished. In front of it, a small furnace is constructed with
vents into the Laconicum, and with a stokehole that can be very
carefully closed to prevent the flames from escaping and being wasted.
Resin is placed in the furnace. The force of the fire in burning it
compels it to give out soot into the Laconicum through the vents, and
the soot sticks to the walls and the curved vaulting. It is gathered
from them, and some of it is mixed and worked with gum for use as
writing ink, while the rest is mixed with size, and used on walls by
fresco painters.

3. But if these facilities are not at hand, we must meet the exigency as
follows, so that the work may not be hindered by tedious delay. Burn
shavings and splinters of pitch pine, and when they turn to charcoal,
put them out, and pound them in a mortar with size. This will make a
pretty black for fresco painting.

4. Again, if the lees of wine are dried and roasted in an oven, and then
ground up with size and applied to a wall, the result will be a colour
even more delightful than ordinary black; and the better the wine of
which it