User:Colorresearcher/Lead white

Lead white is a thick, opaque, and heavy white pigment composed primarily of basic lead carbonate, 2PbCO3*Pb(OH)2, with a crystalline molecular structure. It was the most widely produced and used white pigment in different parts of the world from antiquity until the nineteenth century, when it was displaced by zinc white and later by titanium white. Lead white has maintained relatively consistent production methods throughout various times and regions, yet it has a wide range of applications in different contexts, such as home decoration, art production, and cosmetics. Given its affordable costs and distinctive visual qualities, lead white was particularly favored and generously used by artists in their paintings. However, most art supply companies now explicitly advise against the use of lead white because of the risk that it poses of lead poisoning. Despite this significant and even fatal drawback, its notable occurrence and usage in both paintings and cosmetics serve as evidence of its alarming popularity for centuries.

Production methods
As one of the oldest synthetically produced pigments, lead white has been artificially produced in different cultures using roughly the same production methods since early historical times. A common production method in antiquity involved placing lead shavings above vinegar within a specially designed clay pots, allowing the acidic vapors to react with the lead. As early as 300 B.C., such preparation of lead white from metallic lead and vinegar was probably used in China and later introduced to Japan in the seventh century. In seventeenth century Holland, the "Dutch" or "stack" method of producing lead white improved slightly upon the ancient process by devising an additional step of sealing clay pots in a room filled with horse manure or waste tan bark, which provided a source of heat and carbon dioxide that allowed the combined action of acetic vapors, carbonic acid, and heat to slowly react with the lead to form basic lead carbonate. During the same time, lead white was also manufactured in England and a monopoly was granted for making it. The exclusive control over the production of lead white was not ended until the nineteenth century, when zinc oxide emerged as a rival.

History of use
Lead white is the most important of all white pigments that has been widely used in various contexts across different cultures from ancient times to the present. Until the twentieth century, this highly versatile pigment was utilized in various applications, including enamel for ceramic tableware and bathroom fittings, house paints, and wallpapers. Within the realm of painting, lead white was occasionally used in wall paintings and tempera paintings on paper and silk in early times in China and Japan. Well into the nineteenth century, it was the sole white pigment used in European easel painting and had been widely adopted by artists due to its affordable costs and distinctive qualities, until the advent of zinc white. In modern times, titanium dioxide has largely taken the place of lead white, as it outperforms lead white in certain aspects, especially in terms of safety of use.

Despite its tremendous versatility, lead white has a significant flaw in its production and application: lead poisoning. As a result, using lead white for cosmetics in various cultures is the most hazardous historical application of the substance. In eighteenth century Europe, upper-class men and women powdered their face and body with beauty products containing toxic chemicals to attain the prevailing fashion ideal of white complexion as a sign of their affluence. Lead white, one of the most popular ingredients used in cosmetics to whiten the skin, was favored for its opacity in spite of the well-known risk of lead poisoning. In other cultural contexts such as Greece, China, and Japan, white lead had long been a popular cosmetic foundation to make skin look smooth and pale. Despite its fatal danger of lead poisoning, the use of white lead in cosmetics persisted for an extended period of time in history across many cultures.

Visual characteristics
Given its high refractive index and low oil-absorption index, lead white generally requires a small amount of oil to make workable pastes with high hiding power. It has served to delineate forms in underpainting for the modeling of bodies and for highlights because of its high opacity and adherence. Today, when paintings are X-rayed, the often dense outline of lead white can form a kind of skeleton within a painting. In addition to being used independently, lead white is frequently used to produce tints of other colors. In combination with blue, it appears often in depictions of the sky, and it is commonly used with red and brown pigments to create flesh tones. Besides, admixtures of lead white with other whites such as calcium carbonate and chalk for making opaque watercolor may also be encountered in paintings, especially those created by sixteenth and seventeenth-centuries Dutch artists.

Permanence
Lead white is compatible with various binding media and has remarkable permanence by being unaffected by light. However, its permanence also depends on its relationships to different media. Most of the lead white of European paintings was ground in vegetable drying oil, particularly linseed oil with superior drying properties. Once the mixture has completely dried, it results in a tough and resistant film that is less prone to swelling in organic solvents compared to other oil-pigment mixtures. While lead white locked in a drying oil film and protected with varnish endures for centuries without blackening, it turns black when used in watercolor technique, like in the highlights of old master drawings, due to the presence of hydrogen sulfide in the air.

Notable occurrences
The ubiquity of lead white for much of recorded history makes its occurrences in both western and non-western art widespread. Several examples, significant for their early date, are Fayum portraits from the second century CE. Over eighty Dutch paintings dating from the mid-fifteenth to the mid-nineteenth centuries are found to contain lead white. Lead white can also be found in paintings well into the 20th century, including in the work of major artists such as Picasso. In non-western cultural context, there are a number of occurrence of lead white as a pigment in East Asian paintings, especially murals or silk paintings. The most notable of which are the the Dunhuang cave paintings found in western China, which dated to the ninth or tenth century, as well as the Japanese wall paintings in the Daigoji Pagoda and the Korean mural paintings in Anak Tomb No. 3.