Lithopone
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Lithopone
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Color Index
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Pigment White 5 CI 77115
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Formula
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ZnS 30% / BaSO4 70% or ZnS 60% / BaSO4 40%
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Structure
Lithopone is a co-precipitate of BaSO4 and ZnS. The mix of the two forms is not
separating in the coating.
- BaSO4 cristallise in a rhomboedric system
- ZnS cristallize in a cubic or hexagonal system
Properties
Lithopone pigments were available before zinc sulphide. They have a similar composition
to zinc sulphide, only they are correspondingly weaker due to their barium sulphate
content. They also have poor resistance to chalking. Economically they are cheap
and for this reason they are used as a partial replacement for titanium dioxide.
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Properties of lithopone
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Property
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Lithopone
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Refractive Index
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2
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Density
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4.2
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Oil Absorption
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10-12
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pH
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8-9.5
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Hiding Power
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limited
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Chemical Stability
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good except with acids with pH < 3
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UV Stability
Under UV light, ZnS can degrade and lead to a grayer color. To avoid this degradation,
it is possible to add nicker or iron during the preparation of lthopone, before
calcination cobalt or copper.
Uses
Lithopone can be used in every type of coating.
