Brushes that are in use every day should be placed in water half the depth of the bristles at night, taking care that brushes containing different colors do not come in contact with one another. If they are to be laid aside for any length of time, however, they should be washed with warm water and soap after being thoroughly cleansed with turpentine, and laid away in a moist place.
As a general thing it is better to buy putty already made at a regular paint store, where you may depend upon its being made of good whiting and linseed oil than to make it. Putty should not be used until the work has been primed, for new paint holds the putty very firmly.
White lead is to be judged of by being well ground and possessing the mellowness given to it by age.
It is well known amongst painters that the best article is the most economical, as it works out with more ease, and repays the difference of cost in its better appearance and extra durability. Linseed oil is also better for having due age, for the same reasons as the white lead, working with softness and advantage after parting with the water, which is generally combined with new oil.
In most cases driers are added to paints to cause them to dry more quickly, and a solvent is sometimes required to make the paints work more freely. When the color required differs from that of the main paint used, the desired tint is obtained by adding a staining or coloring pigment. The materials generally employed may, for convenience, be classed as follows:
Bases.—White lead, red lead, zinc white, oxide of iron. Vehicles.—Oils, spirits of turpentine. Solvents.—Spirits of turpentine. Driers.—Litharge, acetate of lead, sulphate of zinc and binoxide of manganese, red lead, etc. Coloring Pigments.—Ochres, lampblack, umber, sienna, and many metallic salts that will be hereinafter mentioned.
White lead may be obtained either pure or mixed with various substances, such as sulphate of baryta, sulphate of lead, whiting, chalk, zinc white, etc. These substances do not combine with oil as well as does white lead, nor do they so well protect any surface to which they are applied. Sulphate of baryta, the most common adulterant, is a dense, heavy, white substance, very like white lead in appearance. It absorbs very little oil, and may frequently be detected by the gritty feeling it produces when the paint is rubbed between the finger and thumb.
White Lead is sold either dry, in powder or lump, or else ground in oil in a paste containing from 7 to 9 per cent. of linseed oil, and more or less adulterated, unless specially marked “genuine.” When slightly adulterated with a very white sulphate of baryta, like that of the Tyrol, the mixture is considered preferable for certain kinds of work, as the barytes communicates opacity to the color and protects the lead from being speedily darkened by sulphurous smoke or vapors. White lead improves by keeping, and when of good quality, will go much further and last much better than when employed fresh; moreover, paint made with new lead has a tendency to become yellow. It should not be exposed to the air or it will turn grey.
Of all the bases used for paints, white lead is the most commonly used, and for surfaces of wood it affords in most cases the best protection, being dense, of good body, and permanent. It has the disadvantage, however, of blazening when exposed to sulphur acids, and of being injurious to those who handle it.
Red lead is produced by raising massicot (the commercial name for oxide of lead) to a high temperature, short of fusion, during which it absorbs oxygen from the air and is converted into red lead or minium, an oxide of lead. The color is lasting, and is unaffected by light when it is pure and used alone, but any preparation containing lead or acids mixed with it deprive it of color, and impure air makes it black. It may be used for a drier, as it possesses many of the properties of litharge; it is also often employed in painting wrought iron work, to which it adheres with a tenacity not equalled by any other paints; it is sometimes objected to for this purpose, on the ground that galvanic action is set up between the lead and the iron. It is also frequently used for priming on wood work, and is especially adapted for hard woods. It is frequently adulterated with brick dust; this may be detected by heating the powder in a crucible, and treating it with dilute nitric acid; the lead will be dissolved but the brick dust will remain. It is also adulterated with colcother, a sesquioxide of iron. Sulphide of antimony, or antimony vermilion, is sometimes used as a substitute for red lead. It is sold in a very fine powder, without taste or smell, and which is insoluble in water, alcohol, or essential oils. It is but little acted upon by acids, and is said to be unaffected by air or light. It is adapted for mixing with white lead, and affords an intensely bright color when ground in oil.