There is quite a demand for these by the building trades, but to manipulate this material profitably requires facilities for handling at little cost. Where the output is large, edge runner mills (chasers) are best adapted, but the kneading machines, similar to those used in bakeries are also quite handy. The colors most in demand are limited to less than half a dozen comprising black, red, brown, buff, and chocolate, very seldom green or blue is desired. Of course the colors must be alkali proof and should be strong, although not brilliant. Usually natural oxides and yellow ochers are selected, while for black mineral black is favored, very seldom vegetable black. The percentage of water in mortar color depends upon the gravity of the pigment and its fineness as well. It is merely necessary to wet up the pigment with water and give it a thorough mixing, so as to form a uniform mass, that will not dry up too readily or permit the water to separate in the package.
This spruce color effect was quite extensively called for before the present modern navy had developed, and it is still a favorite with mariners of the merchant service. When made in paste form, the following composition was in vogue:
To produce this color in ready for use form, mix 70 lbs. white lead in oil, 20 lbs. zinc white in oil, 8 1/2 lbs. French yellow ocher in oil, 1 1/2 lbs. Venetian red in oil and thin with 5 gallons raw linseed oil and 1/2 gallon good turpentine japan. Result close to 9 gallons of paint, weighing 16 lbs. per gallon.
For commercial purposes, where there are no specifications to follow and selling price must be low, the addition of a moderate proportion of inert extending material, would not injure the durability of the paint, although diminishing body and spreading capacity. The paste may then be mixed and ground as follows: 52 pounds dry white lead or sublimed white lead, 13 pounds American zinc oxide, 4 3/4 pounds dry French yellow ocher, 3/4 pounds dry Venetian red, 15 pounds dry asbestine, 14 1/2 pounds raw linseed oil. In ready for use form it would figure out as follows: 70 pounds of the paste, thinned with 26 1/2 pounds raw linseed oil and 3 1/2 pounds liquid drier; will result in 100 pounds or 6 2/3 gallons liquid paint, weighing 15 pounds per gallon. The difference in cost per gallon for material between the paint made without extender and that made with extender is 12 1/2 per cent in favor of the latter, when figuring dry lead at 6 1/2c and zinc at 5 1/2c per pound and linseed oil at 52c per gallon of 7 1/2 pounds.