by Gautam Shah ➔
Lime, Chalk and Gypsum were the first ever whites used. These were available nearly everywhere, and if required its processing was easy. Next to arrive on the scene was Lead white, probably from Greece. Lead white -a carbonate of lead was prepared from metallic lead and vinegar. It was the only white used in art paintings for several generations in spite of knowledge of its poisonous lead content. There were many other whites with varied degree of whiteness, such as Zinc Oxide, Zinc Sulphide, Lithopone (mixture of barium sulphate and zinc sulphide), Barytes (Barium Sulphate). The most widely used white pigment today is the crystal form of Titanium Dioxide (commonly of Rutile and Anatase grades).
White Pigments have high refractive index, and so scatter incident light of all wavelengths effectively, White pigments with high refracting index are also called hiding pigments, whereas others with average refracting index are used as extenders. Extenders help economize use of costly white or colour pigments.
LIME, CHALK AND GYPSUM mainly have Calcium, and to a lesser extent Magnesium. These were popular in ancient times as a drawing medium in soft-rock form, powders wetted with water or mixed with variety of binders. These have low hiding power, but as the only and easy options were popular for long time.
LEAD WHITE has slightly reddish to yellowish tinge that gives warm tonal effect. Lead has positive effect of hastening the drying of oil -the film forming constituent of a paint system. However, Lead is a toxic substance, its presence in old paintings and over walls of old buildings is a health hazard.
ZINC OXIDE has very clean and whiter mass tone than the best grades of Lead white or Titanium dioxide. Zinc white became viable first in water colours (1834) and later in oil mediums. Till the advent of commercial Titanium dioxide it was widely used in paints.
TITANIUM DIOXIDE is the whitest white available any time in history of art and paints. It has 2x times the opacity compared to pure lead white. It is produced through several routes (minerals) but there two important grades Rutile and Anatase. Its chemical stability and heat resistance (for ceramic production) are remarkable. Titanium Dioxide is used for imparting whiteness to Paints, Paper, Foods, Cosmetics, Medicines, Textiles, Ceramics, etc.
White has been used as a representation of whiteness with extreme prudence as well as exuberance. The problem was in its overwhelming opaqueness with highly saturated grades, and it’s poor or uneven transparency in poor grades. Its associated meanings vary in different regions and cultures.