Illumination and Its Development in the Present Day

by Sidney Farnsworth

Gum arabic is prepared in a very simple manner for mixing with colours. Some pieces of this gum are placed in a wide-mouthed jar and covered with cold water. It should be given a stir occasionally, and the following day it will probably be dissolved. It may be strained through muslin if necessary. A few drops of carbolic acid added to it will prevent this solution from becoming sour. It is as well also to provide a loose-fitting cover for the jar to keep dust from the gum.

For mixing the colour a palette-knife is required. A little of the powder colour is placed on the slab and mixed with the palette-knife to a stiff paste with water and a little gum. A glass tube may be used to take the gum from the jar. If this tube is placed in the jar of gum, and the finger placed over the top of it, a small quantity of gum can be easily removed and may be dropped on to the slab by removing the finger. (See [Fig. 29].) This is a much better method than dipping the palette-knife into the gum, as this is very likely to get contaminated with the colour if this is done.

It is not advisable to mix the colour too thinly with water before adding the gum, as one of the effects of the gum is to make the colour flow much easier, and if there is a fair quantity of colour on the slab it is liable to flow over the edges.

After it has been well mixed up with the palette-knife it should be tested to see if it has sufficient gum in it. The student should take a clean brush and paint a small square with the colour on a piece of paper. When this is quite dry it is very easy to tell if it has the proper quantity of gum in it. As mentioned before, if it has too much the colour will look patchy or shiny. To find out if there is enough gum in it, take a small piece of rough paper and rub the patch of colour vigorously with it; if there is insufficient gum to bind the colour it will rub off on to the paper; if there is too much gum, more colour should be added; while, on the other hand, if there is not enough a little more should be mixed with it.

When painting a fresh square of colour for testing purposes it is essential that the brush should be thoroughly washed before painting the new patch. If this is not done the result will be that the colour will be mixed with that already in the brush, and the test will not be a true one. Another important thing is to see that the colour is well mixed with the gum, otherwise one is very liable to get one brush full of colour that is nearly all gum and another with insufficient gum in it.

When the colour is well mixed up with the right quantity of gum it should be thinned out with water and is then ready for use. It should be placed in little saucers, which may be obtained from any artists’ colourman. A small square of glass may be placed over the saucer to prevent the evaporation of the water from the colour, as, if left exposed to the air, this will soon dry quite hard. If it is desired to keep the colour moist for any considerable time, a small quantity of glycerine and honey should be added to it. The colour, however, does not work so well when used as body-colour if this is done.

The following is a good method of keeping body-colour in a convenient form. The colour should be painted on large pieces of glass or slabs of porcelain and allowed to get perfectly dry. It can then be scraped up in the form of a fine powder. An old chisel-knife, or a broken palette-knife, makes a good scraper. This powder requires only a little water to be added to it and the colour is ready for use. It dissolves very quickly in water to form an easy-flowing colour, much superior to colour that has glycerine and honey added to it to keep it moist. Especially is this the case when working on vellum. It dries with a dull, velvet-like surface which shows in strong contrast to brightly burnished gold. If the colour, when scraped up, is not very finely divided it should be rubbed up, in its dry state, on the slab, with the palette-knife or muller, until it is quite fine, as the finer the powder the more quickly will it dissolve.

A complete set of colours for illuminating may be prepared in this way and put into small bottles until required. No gum should be added when using them, as each small grain of colour has its own portion of gum which binds it to the surface on which it is painted.

When it is required to use any of the colours prepared in this way, a small quantity of the powder should be placed in a small saucer and a little water added. It should then be worked up with the finger-tip until it is fluid enough to work well with the brush.

Colours prepared in this way work very well also in the pen, vermilion especially working very well indeed. It is not advisable to use a brush to mix the colour up with, as this method not only quickly spoils a brush, but also it does not mix the colour up nearly so well as the finger-tip.