Is Titanium White acceptable to use as an underpainting white?

[Richard Bingham]

Is titanium white too "fat" to use in underpainting layers? No.

While rutile titanium has an oil absorptive index up to three times that of lead carbonate, a lean, stiff tite white may be no "fatter" out of the tube than lead white. Tite white that's very loose and obviously "oily" out of the tube may have as much as three times the amount of oil as lead white, however.

There is a misconception that the dryness of initial layers before overpainting is related to the "fat over lean" principle. This is not so. "Fat" layers (referring to their oil and/or resin content) are either chubby, or anorexic, whether they are wet or dry, as the question is not whether the paint is dry, but how much oil does it contain?

In fact, as far as the dryness of underlayers is concerned, the best practice is to paint as near to wet-in-wet as possible, working over underpainted layers when they are "dry" enough not to lift or mar if that's indicated, or "cheesy", i.e. well set, but still able to be manipulated, but not bone dry. This way, solvent transfer allows the paint layers to meld into a homogenous mass that will not have stresses or tend toward delamination.

Because pure spirits of gum turpentine (distilled from resin tapped from living trees, not steam-cooked from forest waste) contain hydroxides that react with acids in drying oils to bind free oxygen, it is (and always has been) a solvent superior to petroleum distillates which do nothing to improve the chemistry of drying paint in positive ways.

In general, it is well to lean toward colors with low oil absorptive indices (almost all earth colors) for initial layers. This makes it easy to adhere to the "fat over lean" prinicple. Also, unless the tite white was underbound, and really "constipated" out of the tube (and I've never found Graham's colors to be so) it would also be well to avoid adding additional free oil to the paint in the underlayers.

If you find it necessary to reduce the paint, use a "medium" of oil and turps at a 1:2 ratio. Good turps smells like a pine forest . . . bad turps reeks of creosote.