White lead
White lead is the chemical compound (PbCO3)2·Pb(OH)2. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because its opaque quality made it a good pigment. However, it tended to cause lead poisoning, and its use has been banned in most countries.
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. In any event, white lead has been mostly supplanted in artistic use by titanium white, which is structurally weaker than white lead. 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.
Historically, white lead was produced by the Dutch process. This involved casting metallic lead as thin buckles. These were corroded with acid in the presence of carbon dioxide. Next they were placed in pots with a little vinegar (containing acetic acid). These were stacked up and left for six to fourteen weeks, by which time the blue-grey lead had corroded to white lead. The pots were then taken to a separating table where scraping and pounding removed the white lead from the buckles. The powder was then dried and packed for shipment.
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.
White lead occurs naturally as a mineral, in which context it is known as hydrocerussite
White lead is the chemical compound (PbCO3)2·Pb(OH)2. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because its opaque quality made it a good pigment. However, it tended to cause lead poisoning, and its use has been banned in most countries.
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. In any event, white lead has been mostly supplanted in artistic use by titanium white, which is structurally weaker than white lead. 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.
Historically, white lead was produced by the Dutch process. This involved casting metallic lead as thin buckles. These were corroded with acid in the presence of carbon dioxide. Next they were placed in pots with a little vinegar (containing acetic acid). These were stacked up and left for six to fourteen weeks, by which time the blue-grey lead had corroded to white lead. The pots were then taken to a separating table where scraping and pounding removed the white lead from the buckles. The powder was then dried and packed for shipment.
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.
White lead occurs naturally as a mineral, in which context it is known as hydrocerussite
