CHAPTER I.
The Composition of a Paint.
—Clearly the first thing to be done before studying the subject of paint and colour mixing is to determine what a paint or what a colour is. Without attempting to give a hard and fast definition, it may be said that a paint consists of any pigment, such as white lead, mixed with linseed oil, and thinned by means of turpentine to render it in such a condition that it may be readily applied to the surface of wood, iron and other work by means of a brush. Paint serves the purpose first of preserving the material to which it is applied, and secondly, but not always, a decorative object where the colour is of importance.
The principal pigment used in paint mixing is white lead, but there are many others that are also employed. Many painters look upon paint as necessarily consisting of white lead to which has been added sufficient colouring matter to give the desired tint. As a matter of fact, white lead may be wholly absent from a paint. For example, yellow ochre may be used by itself; iron oxide in the shape of Indian red, purple brown, Venetian red, or Tuscan red forms in itself a good paint if the colour is not objectionable. Again, in the lighter paints we sometimes have white lead replaced by an admixture of zinc white, barytes and other materials of the kind.
The oil used in mixing paint is used to combine the particles or pigment together. That is its chief object, but it is also employed to give a glossy surface and to bring the material to a proper consistency. Turpentine could be used for the latter purpose by itself, but the result would be what is termed a “flat” surface, or an absence of gloss. The turpentine, too, evaporates to a considerable extent. It is generally conceded, among those who have given close attention to the subject, that the durability of a paint depends largely upon the oil used; indeed, it has been likened to the life-blood of the paint. There is not much doubt that the best pigments may be replaced with others somewhat inferior without so much detriment to the quality of the paint as if linseed oil is replaced by some other oil. It is quite necessary that pure linseed oil be used in the manufacture of all paints, and although there are one or two substitutes on the market which may be employed in very cheap work, no attempt should be made to execute a really good job unless pure linseed oil is used. The purpose of the oil in giving a gloss is sometimes assisted by the addition of a small quantity of oak varnish. This is a growing custom among painters, as the gloss produced is decidedly improved by the addition of the varnish and the work shows up well, while the varnish does not in any way detract from the life of the paint, but rather adds to it. This practice is employed more on inside than outside work, where the execution of the painting requires more care than it does inside, owing to the severe atmospheric conditions, which cause any paint work not properly prepared to soon decay.
The base, such as white lead, having been selected, colours are mixed in order to produce the desired hue or tint. Frequently, however, a colour is made by the mixture of several other colours without any white lead at all. A careful examination of the list included in this book will make this clear.
The colour having been determined, oil, turpentine, and driers are then added. The object of the driers is that of causing the paint material to dry quickly. There are several kinds of driers on the market, but the two best known are termed “patent driers,” which is sold in solid form, and the “liquid driers” or “japanners.” Whichever is used the actual quantity employed will depend very largely upon the pigment. Some pigments, say for instance, red lead may be considered in itself a drier, and the addition of any other is unnecessary. Others, like Vandyke brown, dry slowly, and much more driers will be necessary than is the case with white lead. Further on we give some idea of the proportions of materials to be used, but it will be understood that no exact information on the subject will be possible, for reasons that will be explained. It is of the utmost importance to remember that an excess of driers is most objectionable. It often retards instead of increasing the drying quality, it causes cracks and blisters, and above all, it proves very destructive to the paint itself.
The quality of patent driers varies very greatly, some of the cheaper grades consisting largely of material which possesses no drying properties whatever.
Paint Mixing.
—The method of mixing paint does not appear, strange as it may seem, to have received the consideration on the part of practical painters that it deserves. While the manner of mixing small quantities of paint is thoroughly practical and sensible, yet some painters, even when they have larger quantities of the same paint to mix, adopt exactly the same means without thinking it necessary to take advantage of special machinery which is made for the purpose.