Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/309

Rh a thorough mixture of the oil and white lead. This form is much liked by painters, it being more readily miscible with oil and turpentine to make it into paint.

In order to obtain a cheaper product, white lead is frequently mixed with barytes which is distinguished by its white color and great specific gravity. The mixture is often effected in fixed proportions and for certain varieties of white lead, which are known by special names or numbers, remains unchanged. Thus Venetian white consists of equal parts white lead and barytes, Hamburg white of 2 parts barytes and 1 part white lead, Dutch white with up to 75 per cent barytes. The so-called Kremnitz white is a pure white lead. It is produced by placing trays containing a paste made of litharge and either acetic acid or lead acetate upon shelves in a chamber built of brick or wood. When the chamber is filled carbonic acid gas is sent into it and is absorbed by the lead oxide present in the paste.

Zinc White or Zinc Oxide has, in recent years, made great advances in popularity among painters. Compared to white lead, it is as white to yellow. It is indeed beautifully white, very fine, and easily worked. The whiteness is of importance in mixing paints, as the purity of color is retained, while when mixed with lead the yellowish east to some extent destroys the purity of the original color. The fact that oxide of zinc is non-poisonous is a point in its favor of very considerable importance. It is claimed that painters who take care to wash themselves frequently and to take every precaution, are not likely to contract lead poisoning. As a matter of fact, the best of painters are at times careless, while in the rush of work, it is often impossible to take the precautions required. The most important quality of zinc white is its extreme durability.

Properly mixed it will last, at a moderate estimate, twice as long as lead, especially in large cities where the air is impregnated with sulphur derived from burning coal. Lead, in such circumstances, turns yellow or black and quickly