The ingredients employed in the various mixtures used for the different kinds and coats of painting include the following materials: -
White lead, called a "base" in painting work, is a carbonate of lead formed by combining carbonate fumes with the pure lead, by the process of corrosion with acetic acid, the resulting residue being a white powder, which is either sold in that condition, or, more generally, when ground in linseed oil to a pasty consistency.
Red lead is made from oxide of lead, and can be either procured dry or in oil, like white lead. It is used as a drier, for painting iron, or for the first coat, called "priming," on woodwork.
White lead is more used than red lead, being more easily converted into various colours; while it is very dense, and forms a strong permanent covering or protection, being of a good "body" as it is called.
Oil and turpentine are called " vehicles " in paint, because they (Fig.uratively speaking) "convey" the lead on to the surfaces to be covered.
Linseed oil, of a drying kind, is used very greatly in the mixing up of paints, it having the property of being ductile, while it will also dry well and form a good coating.
Turpentine is really an oil extracted from the pine tree, and used to make paint work more easily, and for flatting coats internally, it having a dull effect, in comparison with the linseed oil.
Driers, whether in the form of Litharge, commonly called oxide of lead, or "patent driers," are used to make the oil set all the quicker in forming a coating.
The colouring of paint is done by the addition of various ochres and vegetable matters of different colours called "pigments."
The proportions in which these bases, vehicles, eta, are mixed may vary according to circumstances, and the coats applied, being generally in about the following ratios: -
First coat or priming - 14 lbs. white lead, 1 lb. red lead, 6 pints linseed oil (raw for inside, boiled for outside), 1/2 lb. driers.
Second and third coats - 14 lbs. white lead, 3 or 4 pints oil, 3 pints turpentine, 1/2 lb. driers.
Fourth coat - 14 lbs. white lead, 2 pints oil, 4 or 5 pints turpentine, 1/2 lb. driers.
Woodwork, intended to be painted, comes from the joiner's shop, generally, ready smoothed and clean, so that the first proceeding is to knot it - i.e., to cover the knots over with size, or patent knotting, to kill the turpentine in them, and so prevent them spoiling the finished work. The whole surface is then primed with red lead paint, which satisfies the absorption of the wood. It is then rubbed down with pumice stone, all holes are filled up with putty, and any unevenness obviated, in preparation for the second, third, and fourth coats, each coat containing less oil and more turpentine than its predecessor. Good work should be rubbed down between each coat, which gradually approximates to the finished colour as described, and the final coat very often, from its tint, allows of little lead or body being used.
For ordinary new work the words of the specification are: - "Knot, stop, prime, and paint three oils or coats in best white lead paint"; the only difference between inside and outside work being that "boiled oil" should be used for all parts that are exposed to the sun.
Old work should be well "cleaned, rubbed down, and stopped" before the coats are applied in the ordinary way.
Varnishing is the process of coating plain or painted work with a colourless material called "copal varnish," a mixture of resin and oil or turpentine, which forms a very hard, glossy, and durable coating.
Graining is an additional coat of paint applied on the ordinary four-coat work, and marked or scratched over to imitate the grain of oak and other woods.
Ironwork should be painted with oxide of iron paint, as the lead in the ordinary mixture is said to cause an injurious galvanic action between the two metals.