White Lead Paint

I want to talk about lead paint, but since I’m not an artist but a historian, I have to start the story at the beginning.  The very beginning.

About 400,000 years ago, man learned how to create fire.  Early man had been using fire for about a million years but was forced to use naturally occurring fire.  Whether the first method of creating fire was by striking flint against pyrite to produce a spark or by using a “fire plow” (think of Tom Hanks in Castaway, where one piece of wood is rubbed against another to create friction and heat) is uncertain, but man had begun the long process of mastering fire.

About 40,000 years ago, some human learned to cover the leftover coals of a fire with dirt, keeping them to use the next day to start a new fire.  While removing the dirt, he noticed that some of the coals had turned a dark black and when these coals were ignited, the fire they produced was noticeably hotter than a wood fire.  The discovery of charcoal—how to make it and the realization that it burned both hotter and more efficiently—opened the way to the discovery of metallurgy.  

Some metals—like gold, copper, and silver—occur in nature in their metallic forms.  Finding these would have been an early introduction to metals.  Early humans would have noticed changes in some stones when those had been heated in campfires or in kilns to produce pottery.  For instance, copper nuggets might have been accidentally smelted from ores when naturally occurring copper minerals were exposed to fire.  By 5000 years ago, copper ore was being smelted to produce native copper.  This was the start of the Chalcolithic or Copper Age, a period that is usually skipped over in history classes because within a few years, these neolithic scientists had discovered that adding tin to copper produced bronze—a metal that is harder and more useful than copper.  

By now, you can imagine that early man got busy testing every strange looking rock he could find—which is probably how lead was discovered in Mesopotamia about 3500 years ago.  Lead was an extremely useful metal, too.  Though it takes about 1000°C to smelt the lead out of the ore, once its out, lead itself melts at 327.5°C and is wonderfully malleable.  The Egyptians made an amazing array of dishes and tools from the metal.

About 400 BC, the Egyptians noticed that lead that was exposed to vinegar and horse manure developed a white powder on its surface.  This powder could be mixed with water.  The white powder could also be mixed with honey and egg white and then used in cosmetics and paints.

The Romans loved using lead.  Besides the usual tools and dishes, they created lead pipes to bring water into their cities.  (The Latin word for lead, "plumbum," is where we get the term "plumbing.").  Lead was used for coinage, utensils, statues, roofing—hell, the Romans even created standardized bullets, called glandes, for their slings.  The Romans also had lots of horses and, since vinegar was a byproduct of winemaking, they were able to produce even more of that useful white powder.  Suspended over a fire of burning horse manure, the Romans heated a vat of boiling vinegar with a bar of lead suspended over it.  The white corrosion that formed on the lead bar could be scraped off, ground into a powder, and used in everything from paints to medicines.

Note.  Yes, this was all very toxic and deadly.  And the Romans actually knew this, but the convenience of using the lead outweighed the health concerns.   If this sounds like our society and a host of things we use and consume despite the fact that we know they aren’t good for us, well… Hail Caesar!

Now, let’s move forward to the 14th century, in which the Dutch improved on the Roman method.  In a process called the Dutch Stack lead process, a series of vinegar pots—each with a lead bar suspended over it—was buried under a pile of horse manure.  (Curiously, no other form of manure works.). The fumes from the vinegar corrode the lead, creating a layer of lead acetate, which reacts with the fumes from the carbolic acid from the horse manure to form lead carbonate.  The lead carbonate forms in layers, which can be scraped off and collected.

An artist, who until paint was commercially available in tubes in the nineteenth century, had to be an amateur chemist, would put the “white lead” on a flat stone and grind it into a fine powder, that would then be mixed with either egg and water to form a tempera paint, or with linseed oil or walnut oil to make an oil paint.  The artist had to go through this process every few days since the paint would not keep.

This lead white (also known as white flake or cremnitz) was a very good white paint.  It was highly valued by artists for centuries due to its exceptional qualities:  high opacity, (allowing for effective coverage with fewer layers) and a slow drying time (which was beneficial for blending and wet-on-wet techniques), a smooth, buttery texture (that facilitates easy application and impasto), and its flexibility that reduced the risk of cracking).  Lead white also provided a brilliant, pure white color, that was lightfast, ensuring the longevity of artworks.  It was also versatile for mixing with other pigments without altering their hues significantly and was often used for underpainting. 

Leonardo da Vinci used white lead mixed with walnut oil as an undercoat for both the Mona Lisa and The Last Supper.  The layers of thick paint on The Starry Night by Van Gogh include white lead.  Paintings by Hieronymus Bosch, Vermeer, Botticelli, and Jan Van Eyck all contain white lead paint.

In the nineteenth century, artificial dyes made from coal tar replaced a lot of the pigments that had been used for centuries.  Toxic paints quickly disappeared, one by one, as good artificial pigments were created in the laboratory.

Besides being used in art, leaded paints were widely available for house paints.  The thick opacity meant that fewer coats were needed and the lead content made the paints waterproof and durable.  Ships, houses, barns and commercial buildings were routinely painted with lead-based paints.  As realization grew of the dangers of the toxicity of lead, there was a movement to ban the paints, which happened in the 1970’s.

It surprises people to learn that lead paint for artists is still available, and is still widely used by artists, for the benefits it has that are listed above.  Artists’ lead-based oil paint is a little more expensive and it comes with a lot of warning labels about toxicity, but it is still the best white oil paint on the market.