White lead, the base or foundation, should be pure, but dealers have many means of adulterating it with sulphate of baryta, or barytes, gypsum, or plaster of paris and carbonate of lime, or common chalk, all of which are detrimental. Linseed oil, the purest raw oil, should be used, but this is often adulterated with fish oil or cotton-seed oil. The next requisite is pure black, in order to form a gray or lead color. With these ingredients the priming is formed. The white lead is beat up with the raw oil until of paint-like consistency, then a little of the black is added to form a clean lead color. Some add driers, such as brown japan or japan gold size, but many prefer to use none whatever. The priming thus made is now spread on the wood, and the painter runs the job out in the drying- shed or other convenient place to dry. The oil of the priming gradually leaves the pigments, white lead and black, and seeks the interior of the wood, sucked in, as it were, by capillary attraction, and the pigments are thus virtually strained and left upon the surface in a semi-dry porous state, while the oil that entered the wood, not being a gummy or filling substance, stains the interior of each little pore only. Next, a coat of white lead and oil of similar consistency is put over it.

The oil from this coat is absorbed in by the porous pigments, through which it passes and spreads itself over the stain which the first coat gave to the pores, and the second coat pigments are strained and left porous, so on until possibly five coats of lead color are given, by which time the pores may have become filled by the successive layers of oil, and the pigment on the surface too, is finally cemented together or partially so. This is called the foundation, and it was the only known way to paint a carriage for many years.