Barrow, John [Editor]
Dictionarium Polygraphicum: Or, The Whole Body of Arts Regularly Digested: Illustrated with Fifty-six Copper-Plates. In Two Volumes (Band 2) — London, 1758

Page: 374
DOI Page: Citation link: 
https://digi.ub.uni-heidelberg.de/diglit/barrow1758bd2/0403
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upper piece round ; anal at the bottom a bung to let out the wa-
ter and earth, when fufficiently ground.

To have a wafh then, the trough is filled with common wa-
ter, into which they caff, thirty or forty pounds of quickfilver,
and two or three gallons of matter remaining of the firft lotion.

Then turning the winch, they give motion to the upper part
of the mill, which grinding the matter and the quickfilver vio-
lently together, the particles of the gold and filver become the
more eafily amalgamated therewith : This work they continue
for four hours; when, opening the bung, the water and earths
run out, and a frefh quantity is put in.

The earths are ufually paffed thus through the mill three times,
and the fame quantity of mercury ufually ferves all the three
times. When there is nothing left in the mill but the mercury
united with the gold and filver which it has amalgamated, they
take it out, and, warning it in divers waters, they put it into a
ticking bag, and put it in a prefs to fqueefe out the water, and
the loofe quickfilver; the remaining quickfilver they evaporate
by fire in a retort, &c.

Of WASHING maps, piRnrcs, &c. By Warning is meant
the illuminating maps or pictures with proper colours.

The inftruments and materials ufed in Warning are chiefly
thefe few following; : i. Alum water. 2. Size or gum water.
3. Liquid gold or filver. 4. Pencils. 5. Colours. See each
under its proper article.

Of the practice 0/" Washing, i. Wet your pictures that you
arc to colour over, with alum water, for that will prevent the
colours from finking in, and will alfo add a luftre to them ; and
not only make them appear fairer, but alfo keep them from
fading.

2. Let the paper, thus wafhed with alum water, dry of itfelf,
before you lay the colours on, or before you wet it a fecond or
third time: For fome paper will require wetting four or five
times.

3. This Warning of the paper with the alum water is to be
done with a large pencil-brufh.

4. But, if the pictures are defigned to be varnifhed after they
have been coloured, inftead of the alum water, it will be be ft to
fize them with new fize, made of good white ftarch ; do this
with a very fine brufh, and you muff be very exact in doing it
all over, for, if there be any place left undone, the varnifh will
fink through.

5. The pictures, &c. being thus prepared, you may proceed
to the laying on the colours, according to direction, Anting
them to the life of every thing, as nearly as you poffib'y can.

6. Having painted the picture, you may fize it over as is before

directed.
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