PW 4

Zinc white

(PW4) is a cool, semi-transparent white pigment of zinc oxide, used in artists' paints since the 18th century, known for its low toxicity and clarity, but debated in oil paints for potential brittleness; it gives a thin, clear white color (as opposed to opaque titanium white) and is used as a mixing white to soften other whites.

It is important to use this color correctly (e.g. applying it thinly or as a top coat) to avoid cracking.