Dictionarium polygraphicum. Whites for painting in miniature.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol II.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
The best white that is pretended to be fold for painting in water colours, is flake white, which is better than white lead ground; and if it be pure, far exceeds it in beauty, because white lead is apt to turn blackish, especially if it be used in a hard warer.

But some recommend a white made of pearl or the whiter parts of oister-shells, redue'd into an impalpable powder so soft, as to seel like grounds of starch or hair powder: this is by some call'd pearl-white; but it is difficult to be come by. This white will mix well with any colour.

But if you use white lead, first rectify it with white-vine vinegar, this will cause a fermentation, and the white will soon settle; then pour off the vinegar, and wash it with common water. The method of washing it is thus:

Put the Powder into a glass of water, stir it about, and presently pour off the water, while it is white, into some other clean glass or veslel; let it settle, and then pour off the water from it, and it will be excellently fine.

When this white is settled, put to it as much gum-water as is necessary to bind it or give it a glaze.

It is observable, that white lead will turn black, if mix'd with water that comes from iron or clay; that is, in the space of a month or two, you may perceive those places where it lies thickest ting'd with black, and if it be mix'd with any other colour it will soon change or alter it.

Some recommend the powder of egg-shells of the brightest colour and well clean'd and wash'd, as very good to be ground with gum water; or you may put about a twentieth part of clear white sugar candied to grind with it in water; grind it as fine as possible, that is, to the state of what is call'd an impalpable powder, and then use it.

Some say it is better, if some rectified spirits of wine be pour'd on it, which will clear it from any dross that may be in it; this (as it is very probable) must be pour'd off, when the spirit of wine has done its work, and then the parts left behind, must be mix'd with gum-water again.

But it has been found by experience, that egg-shell powder is of very great service as a white in water-colours, and that that it self and the powder of oister-shells well rectified and mixed with the white of an egg well beaten, will make an extraordinary mixture in other colours, and will correct them from changing or altering their qualities.

But as for white for illuminating of prints, the clear white of the paper is proper to be left uncolour'd; and if it happens that the paper is apt to sink, or to spread any water-colour that is laid upon it more than is necessary, then the way to correct it is as follows:

Fix the paper in such a station, as may only receive the colour you lay on to glaze, just as far as you design'd it; then take some starch boil'd and prepar'd in water of a middle strength, and with a large painting-brush stroke it over the back of the print; and after it has been well dry'd in the air or sun, put the print in a book with a weight upon it, to take out the crumpings, which it may receive by wetting of it; and so will any print be render'd fit to receive water-colours, and prevented from running farther than we would have them.

There is a sort of earth that comes from China, that is of a very soft nature, and very white; which does better in watercolours than any of the rest; but it is very scarce.