Paint pigment

From Citizendium, the Citizens' Compendium
Jump to: navigation, search
This article is developing and not approved.
Main Article
Talk
Related Articles  [?]
Bibliography  [?]
External Links  [?]
Citable Version  [?]
 
This editable Main Article is under development and not meant to be cited; by editing it you can help to improve it towards a future approved, citable version. These unapproved articles are subject to a disclaimer.

Paint pigments are used to produce, singly or in combination, the appearance of commercial and fine art paints, and related coatings such as pastel and colored pencil. Whites and blacks may be used alone, or to adjust the color saturation of mixtures.

Pigments combine with the paint base to produce effects such as reflectivity; this is notable in the brightness or darkness of whites and blacks.

Colors

Inorganic pigments may be native earths or minerals, heat processed minerals, or synthetics. Organic pigments may also be synthetic, or from animal or vegetable sources. Classical pigments are all powders; a lake is made by adsorbing a soluble dye on a solid base.[1]

The names of many classical pigments are still used, even if the color is made synthetically.

Whites

Among the most common, although not the brightest, white, is calcium carbonate in the form of precipitated chalk. Titanium oxide and zinc oxide are much more highly reflective.

Blacks

Most black pigments are the residue from combustion of various materials, although Mars black is iron oxide.

Reds

Synthetics have replaced many of the classical earth pigments, whose resistance to fading is inferior to the artificially produced equivalents. Mars colors are iron oxides.

Alizarin, the base of many reds, originally came from the madder plant, but is now synthesized. It is a dye, which is made into a lake onto such bases as aluminium hydrate.

Yellows and oranges

Most plant-derived yellows were replaced by chromium-based compounds, which, in turn, have been replaced by cadmium or cadmium-barium compounds in professional use. Chromium remains too toxic for childrens' uses.

Hansa yellow is a synthetic.

Ochres are washed and refined clays, sometimes mixed with chromium colorants.

Browns

Natural and refined clays, including raw and burnt umber, are the most common browns in art use.

Greens

Viridian, a mineral, is a standard, although the lake of pthalocyanine green is also common.

Hooker's Green was originally a mixture of Prussian Blue and gamboge, but is now made from pthalocyanine blue and cadmium yellow.

Blues

Ultramarine, originally made by grinding the semiprecious stone lapis lazuli, has been made artificially since 1828. An aniline dye made into a lake, pthalocyanine blue, is also in common use, with trade names including Winsor Blue; it replaced Prussian Blue (ferric ferrocyanide).

Safety

Some classical pigments, such as Paris Green, an arsenical compound, are too dangerous for general use; lead based pigments are a major public health problem in commercial paints but have limited use in artists' colors.

Other pigments have professional applications, but, for example, cadmium based pigments are not used in children's paints.

References

  1. Ralph Mayer (1970), Chapter 2: Pigments, The Artist's Handbook of Materials and Techniques (Third ed.), Viking