Cadmium pigments

Cadmium-rich hemimorphite crusted on smithsonite

Cadmium sulfide

Brilliantly colored, with good permanence and tinting power, cadmium yellow, cadmium orange and cadmium red are familiar artists’ colors, and are frequently employed as architectural paints, as they can add life and vibrancy to renderings. Their greatest use is in the coloring of plastics and specialty paints, which must resist processing or service temperatures up to 3,000 °C (5,430 °F).[4] The colorfastness or permanence of cadmium requires protection from the element's tendency to slowly form carbonate salts with exposure to air. Most paint vehicles accomplish this, but cadmium colors will fade in fresco or mural painting.

The following are commonly used as pigments in artists' paints:

• Cadmium yellow is cadmium sulfide (CdS), C.I. Pigment Yellow 37.
• Cadmium sulfoselenide is a solid solution of CdS and cadmium selenide; depending on the sulfur-to-selenium ratio, C.I. Pigment Orange 20 or C.I. Pigment Red 108 is obtained.
• Zinc cadmium sulfide is a greenish, solid solution of CdS and zinc sulfide, C.I. Pigment Yellow 35.
• Cadmium yellow is sometimes mixed with viridian to give a bright, pale green mixture called cadmium green.

When first introduced, there were hardly any stable pigments in the yellow-to-red range, with orange and bright red being very troublesome. The cadmium pigments eventually replaced compounds such as mercury(II) sulfide (the original vermilion) with greatly improved lightfastness.

Cadmium pigments are known for excellent lightfastness, although the lighter shades can fade in sunlight.[5] A cadmium yellow paint was frequently used on Bob Ross' TV show The Joy of Painting.

Borosilicate glass colored with cadmium compounds.

Cadmium compounds are utilized in coloring borosilicate glass[6] used by artists in lampworking. The palette is often referred to as "cadmium colors" or "cadmium-based colors" and is marked by uniquely bright and saturated tones not found in other colored glass. Cadmium pigments used in borosilicate have a relatively short history, with the first commercial formulations hitting the market in 2000 under the name Crayon Colors by Henry Grimmett of Glass Alchemy.[7]

Cadmium-compound-containing glass exhibits a characteristically low heat tolerance when melted, and therefore must be treated with caution when lampworking to avoid boiling off of the cadmium sulfide. CdS has a boiling point of 980 °C (1,800 °F), putting its maximum temperature tolerance as a pigment not far above the working temperature range for borosilicate, which has a softening point of approximately 850 °C (1,560 °F).[8][9]

Cadmium orange cast-iron pot

Cadmium sulfide is not very toxic (LD₅₀ above 5,000 mg/kg) when used as a pigment, although acute exposure to cadmium vapors from welding is harmful.[3]

The cadmium pigments have been partially replaced by azo pigments. These have significantly inferior lightfastness,[10] but still good,[11] and they have the advantage of both being cheaper and non-toxic. In some countries, consumer activists such as Michael Vernon in Australia were successful in banning the use of cadmium pigments in plastics that could be used for toy manufacture, owing to the toxicity of cadmium.

In December 2013, the Swedish Chemicals Agency (KEMI) proposed a case to the European Chemicals Agency (ECHA) in favor of restricting or banning cadmium use in artists’ paints, as cadmium in pigments used in other types of paints was already restricted and regulated via TARIC codes and REACH Annex XVII. This proposal stated that cadmium in the body leads to increased risk of bone fractures and breast cancer as well as an array of environmental impacts, and that paint washed down the drain is absorbed by crops that are then consumed, increasing the average dietary cadmium intake. This can cause an array of health effects, including kidney and liver damage, skeletal damage, several types of cancers and death.[12] [13] [14] KEMI's proposal was ultimately declined.

In a June 2015 article of Just Paint, published by Golden Artist Colors, the company argued against KEMI's proposal, offering that "There are no alternatives that match all of the characteristics of cadmium pigments." This statement was also included in Golden's response to KEMI's request for information on cadmium-pigmented artists’ paints while the agency was composing its ban proposal. The article also stated that a ban would be technically feasible for some artists, but not all, and that "cadmium colors are not for use by children, should not be spray applied or sanded, and unless one is properly protected from exposure and in a non-household setting, use of dry cadmium pigment should be avoided." [15] [16]

Inhalation poses the greatest risk from cadmium pigments, though the chemical is very low-risk when sealed within a pigment particle because of its insolubility. The use of chalk pastels containing cadmium colors is among the highest risks for artists, as these pastels create a dust that can be inhaled.[17]

Cadmium is introduced into the body most commonly through smoking, and in individuals who do not smoke, the next most common instance is through dietary consumption.[18]

• 
  Winslow Homer, "Hunter in the Adirondacks" (1892)
• 
  Vincent van Gogh, "Grapes, Lemons, Pears, and Apples" (1887)
• 
  Claude Monet, "Wheatstacks (Sunset, Snow Effect)" (1890–91)
• 
  Claude Monet, "Still Life with Apples and Grapes" (1880)

• List of inorganic pigments

• Fiedler, I.; Bayard, M. A. (1986). "Cadmium Yellows, Oranges and Reds". In Feller, R. L. (ed.). Artists' Pigments: A handbook of their history and characteristics. 1. Oxford University Press. p. 65–108. ISBN 9780894680861.

• "Cadmium and compounds". National Pollutant Inventory. Archived from the original on 10 December 2006.
• "Cadmium yellow". Pigments through the Ages. WebExhibits.
• "Cadmium orange". Pigments through the Ages. WebExhibits.
• "Why are cinnabar, vermilion, and cadmium orange colored?". Causes of Color. WebExhibits.
• Cadmium yellow, ColourLex
• Cadmium orange, ColourLex
• Cadmium red, ColourLex