Dictionarium polygraphicum. Of preparing colours. Tempering of colours. Help the defects of colours. To burn or calcine colours. To prepare shadows for colours.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
TEMPERING of COLOURS.
Take a little of any colour, and put it into a clean shell, and add to it a few drops of gum water, and with your finger work it about the shell, and let it dry, and when dry, touch it with your finger; if any colour comes off, you must add stronger gum water; but being dry, if the Colour glister or shine, it is a sign there is too much gum in it, which you may remedy, by putting in fair water.

To HELP the defects of COLOURS.
Some Colours, as lake, tember and others which are hard, will crack; when they are dry in this case in tempering them, add a little white sugar candy in very fine powder; which mix with the Colour and fair water in the shell, till the sugar candy is dissolv’d.
These Colours, umber, Spanish brown, Colen-earth, cherry-stone, and ivory-black, are to be burnt before they are ground or wash’d.

To BURN or CALCINE COLOURS.
This is to be done in a crucible, covering the mouth of it with clay, and setting it in a hot fire, till you are sure it is red hot through; which done, being cold, wash or grind them as before directed.

To prepare SHADOWs for COLOURS.
White is shaded with black, and contrary-wise, yellow with umber and the okers, vermilion with lake, blue bice with indigo, black-coal with roset, &c.