PW 7 – zinc sulfide

Together with barium sulfate, it makes lithopone

Manufacturer/ product code:  Kremer / 46350
Chemical Description:  zinc sulfide
Color: white
Color Index: PW 7
Date: 1852

PW 7 – Zinc Sulfide is an inorganic white pigment composed of zinc sulfide (ZnS). Known for its soft, slightly warm white tone, PW 7 has historically been used as a pigment in paints, coatings, and plastics, as well as in optical and luminescent applications due to its unique physical properties. Unlike more opaque whites such as titanium or zinc oxide, zinc sulfide is moderately transparent, making it valuable for subtle tints and special effects.

Chemically, ZnS is stable under normal atmospheric conditions, with good resistance to light and heat. It is insoluble in water and most solvents, although it can slowly oxidize to zinc sulfate under prolonged exposure to moisture and oxygen. Its thermal stability and inertness make it suitable for incorporation into industrial paints, varnishes, plastics, and artistic media such as oil or tempera paints.

In practical use, PW 7 exhibits moderate opacity and low to moderate tinting strength, making it suitable as a softening agent in mixtures with other pigments or for creating subtle pastel shades. Its transparency allows for layering effects and smooth transitions in paints. Historically, it has been employed in decorative and artistic materials where a gentle white or a slightly translucent effect was desired.

From a conservation perspective, zinc sulfide is relatively inert and does not readily react with other pigments or binders under normal conditions, although it may darken slightly upon prolonged oxidation.