White Lead - Paints

Paints

White lead has been the principal white of classical European oil painting. There have been claims that it is partly responsible for darkening of old paintings over time, reacting with trace amounts of hydrogen sulfide in the air to produce black lead sulfide. Other authorities dispute this; the most traditional view is that impermanent pigments and dirty varnish (which is often cleanable) are more likely responsible for darkening.

Paintings and the role of varnish, which might protect the white lead yet itself darken, aside—according to Michelle Facini, a paper conservator at the National Gallery of Art, lead carbonate to lead sulfide is indeed what happens to some lead chalks/paints in drawings and watercolors and other works done on paper and unvarnished. Varnish is meant to be removable from an oil painting, to strip off when it dirties or cracks; but on paper it soaks through and becomes inseparable from the paper fibers, ruinous as it ages. This is why works on paper are never, or should never, be varnished. Thus, far more frequently for paper works than for paintings, lead white was exposed directly to sulphur in the air (particularly hydrogen sulphide from untreated coal gas, say in 19th century industrial London, for example) to turn to the black sulfide.

In any event, white lead has been mostly supplanted in artistic use by titanium white, which is structurally weaker than white lead. Critics argue that many of these substitutes are much less permanent. White lead is less used by today's painters, not because of its toxicity directly; but simply because its toxicity in other contexts has led to trade restrictions that make lead white difficult for artists to obtain in sufficient quantities. Winsor & Newton, the English paint company, was recently restricted from selling its flake white in tubes and now must sell exclusively in 150mL tins.

In the eighteenth century, white lead paints were routinely used to repaint the hulls and floors of Royal Navy vessels, to waterpoof the timbers and limit infestation by teredo navalis worms.