The pigment number for basic lead carbonate is PW 1; zinc oxide is PW 4. Look on the label of the paint tube or in the manufacturer’s information brochure, web site, or whatever, to see what the pigment is, or pigments are, in any paint you’re considering using or buying. My recommendation is that you avoid PW 4 and any white that has it as an ingredient if you care how long your paintings will last.
Some companies add zinc oxide to their lead whites, and this is NOT good for the long-term life of the painting. So I recommend avoiding any variety of lead white (or any white) that contains zinc oxide (PW 4).
In my book, I mention Flake White often. It’s important to understand that real flake white is basic lead carbonate pigment bound in linseed oil, walnut oil or poppy oil. Why it’s important to mention this is that some paint companies are adding zinc oxide to their (so-called) Flake Whites, and zinc oxide is a problematic pigment that can cause delaminations in oil paintings. So please understand that whenever Flake White is mentioned in my book, what it means is lead white, not lead white with zinc oxide (aka zinc white) as an ingredient.
More on Zinc White / The Trouble with Zinc Oxide
Zinc white has been shown quite conclusively to be a cause of not only embrittlement, but delamination in oil paintings, even when it’s a minor component in mixtures with titanium dioxide (titanium whites) or basic lead carbonate (flake whites.) Marion Mecklenburg did not mention any percentage that he felt was safe at the conclusion of his testing. So anyone who cites a certain percentage as a safe limit is basing that assessment purely on wishful thinking.
Zinc oxide was/is added to many companies’ titanium whites to add physical strength to the resulting paint films, because titanium dioxide by itself does not make for strong, durable paint films when used in an oil binder. That can now be recognized as not as good an idea as it was once thought to be.
Lead White – PW1
Lead white is the most durable of all oil paint whites; in fact, of all oil paints.
It goes by various names, including Flake White, Cremnitz White, Silver White, and Lead White.
They’re all names for varieties of basic lead carbonate. They once denoted white lead made by different processes, but these days the pigment is all pretty much the same. Some manufacturers call their white lead Cremnitz White if it’s only basic lead carbonate, or Flake White if it’s a mixture of basic lead carbonate and zinc oxide, or Flemish White if it’s basic lead carbonate with calcium carbonate or something else. The ones containing zinc oxide PW 4 are best avoided. Rublev avoids this confusion by calling their lead white with no other pigments “Lead White”.
White lead paint is a bulk dryer, which means homogeneous drying over the paint film; lead white builds a stronger paint film than other oil paints.
Lead white is among the leanest of oil paints. It is also highly resistant to the action of ultraviolet light, which causes the embrittlement of materials. Lead white resists the ravages of time better than any other oil paint. It is very dense, yet somewhat flexible. Generally speaking, oil paints formed with lead white are structurally superior to the films produced with zinc white, titanium white, and titanium-zinc mixed whites, whose pigments lack lead carbonate’s affinity for oil, and which perhaps do not offer the same resistance to UV rays as lead.
I should mention that there are two companies who currently offer lead white made following to old Dutch stack process, the way it was made in the 19th century and earlier. Michael Harding has it available as oil paint, and Natural Pigments has it as dry pigment. These are essentially the same kind of whites used by the Old Masters.
The dangers of lead poisoning are slight in the case of flake white in the form of oil paint, as distinct from loose powder, as long as it is kept out of the mouth and nose and away from cuts in the skin. It cannot be inhaled, as its particles are encased in a film of oil and bound together by it.
I use Rublev Lead White #2 as the white because its slower drying is advantageous for painting skies.
Brands that have good quality lead white oil paints include: Rublev, Micheal Harding, Vasari, and Williamsburg. I haven’t tried RGH, so cannot comment on them one way or another, though I have heard good things about it.
Titanium white bound with safflower, sunflower or poppy oil will dry very slowly unless the manufacturer has added drying agents. Sunflower oil is the worst in that regard, and it has recently been found to re-liquify in some instances after it was supposedly dry. I have a sample on one of my color chart panels that stayed tacky for ten years.
Some brands use more drier than others. Sometimes the wrong proportion of certain driers can actually cause the opposite of the intended effect, and make the paint dry more slowly or not at all.
Titanium white in safflower or sunflower oil is potentially problematic, and the more so if it contains zinc oxide (PW 4.)
If longevity is an important concern to you, then titanium white, even the best of them, is not a good choice. It isn’t likely to last as long as lead white.
Titanium white (PW 6) is more opaque than lead white (PW 1), however, lead white is sufficiently opaque for all practical purposes, including underpainting. Opacity is not the only concern in underpainting. There is drying time to consider, and film strength, both of which are much better with lead white. Furthermore, the durability of all the paints in the ensemble is improved when lead white is the white in the painting, in the underpainting, and/or in the ground. Titanium white does not provide that benefit, so oil paintings done with titanium white in the underpainting will not last as long as oil paintings in which lead white is the white used in the underpainting, all else being equal.
Price might have a bearing on quality where titanium white is concerned, because there is more than one kind if titanium dioxide pigment, and the cheaper varieties are likely to be made with an inferior grade. But the presence of zinc oxide in titanium white is perhaps the most important concern, regardless of price. You would be best advised to avoid any oil paint that has zinc oxide (PW 4) in it.
[A technical explanation for titanium white’s tinting power is offered by George O’Hanlon: “Titanium dioxide (rutile) has one of the highest refractive indices of any known pigment today and at the particle size it is typically available, it also scatters more blue wavelength light and hence has a bluish bias in white, so it not only more easily tints colors than lead white, but also is bluish, unlike lead white.”]