I've always been a little puzzled by the many white paints available for use in watercolor and oil painting. Believe it or not, this is a topic of discussion among some of my artist friends. (Go ahead and say it, we're nerds.) After doing a little research, I found why choosing the right white matters.
WHAT ARE THEY?
The most common artists' white paint pigments are Zinc White, Chinese White, Titanium White, and Lead White. In each of the following posts, I will discuss the properties of each pigment. The last post will be a reference chart comparing the pros and cons of each paint.
Let's start with the oldest of the whites, Lead White (also known as Flake White or Cremnitz White). It dates back to the Ancient Greek and Egyptians. It was originally made by filling lead jars and pots with vinegar (which is an acid) and burying the pots in manure piles, an ancient source of generating heat. The lead disintegrated into a white powder that was white lead.
Lead White has great opacity and is known for it's buttery consistency. It produces very intense, warm color mixtures. The color and textural qualities of the "old masters'" paintings come from the use of lead white. The particular warmth of the works of painters such as Monet also comes from their use of Lead White and cannot be produced by any other white oil paint.
The pigment of Lead White is basic lead carbonate; it is very toxic. That is why you never see this color in water-dilutable paints; it would be too dangerous to use. However, when incorporated into an oil paint and used in a conventional manner, it can be used safely.
Because of its lead content, manufacturers have developed a white paint similar to lead white, but without its toxicity. Gamblin, for instance, has created flake white replacement, which has moderate tinting strength and maintains most of the working properties of flake white.
Source: Wet Paint Art