The best prepared colours are undoubtedly those sold in the form of cakes, as they are the purest. The other forms contain a considerable amount of glycerine, which does not improve the colour, but enables them to be kept moist for quite a long time—a greater advantage to the artists’ colourman than to the artist.
Tube colours contain more glycerine than those sold in pans. The great advantage, however, that tube colours possess is their convenience. A small quantity of clean colour can be squeezed out and the cap replaced on the tube, thus keeping the rest of the colour free from dust. The admixture of so much glycerine with the colour, however, often prevents it from drying quite flat when used as body colour.
One word of warning may be useful here: gum should not be mixed with water-colours. This is often recommended in books on illumination, but it is not only unnecessary but it entirety spoils the appearance of the colour. There is always quite sufficient gum mixed with the colour, and there is nothing specially beautiful about the shiny appearance caused by an excess of gum in the colour.
Without a doubt the best colours for the illuminator to use are powder colours. They are mixed with gum arabic and water. Care should be taken to get the right quantity of gum mixed with the colour. If there is not sufficient to bind the colour it will rub off when dry, while, on the other hand, if there is too much, it will dry patchy, and if very much in excess it will present a shiny appearance. Experience will soon show the exact amount necessary.
One very great objection that is often urged against the use of powder colours is their inconvenience, but if these are prepared in the manner described below they should not be more inconvenient to use than the ordinary ready-prepared water-colours.
For illuminating, where the work is required to be lasting, none but permanent colours should be used; but when making designs which are for temporary use only it is foolish to use expensive colours like aureolin and cadmium yellow when the same effect can be obtained with the various shades of chrome yellow, which is much cheaper, although notoriously fugitive.
It is best to buy the colours ready ground. A china slab or a piece of plate glass may be used to mix the colours on, or the back of a large white plate might serve in lieu of these. When it is necessary to grind the colour a muller is used for this purpose. (See [Fig. 29].)
Slab & Muller.
Palette Knife.
Scraper.
Saucer, with Cover.
Method of taking Gum from Jar.
Fig. 29.