I used to think that lead white dries quickly in oil and promotes drying when it is a component of mixtures. It’s true that lead white dries faster than titanium white, which is a slow drier, but it is really just normal in overall drying speed.
This has been illustrated for me this week. The background of the painting I’m working on is a gradation of mostly lead white to lead white with a fair bit of raw umber. Raw umber dries quickly and promotes drying when it is a component of any mixture. Over the course of several days, I’ve observed the painting dry progressively from one edge to the other—the more raw umber, the faster the drying. The lead white part of the painting has not dried quickly at all.
Modern lead whites are made with a pigment called “basic lead carbonate.” Historically, lead whites were less pure. They contained basic lead carbonate, as well as other lead compounds that do dry fairly quickly. So older lead whites, such as those made using the traditional stack process, would likely act as driers. It may be that if you bought some stack process lead white from Natural Pigments and mulled it with oil, you’d have a fast drying white.
Other than that, you can make lead white dry more quickly by adding a small amount of lead napthenate or other drier, just as with any other oil paint. Or you can mix in some umber.