Cadmium pigments

Cadmium Orange
Color coordinates
Hex triplet	#ED872D
sRGBB  (r, g, b)	(237, 135, 45)
CMYKH   (c, m, y, k)	(0, 43, 81, 7)
HSV       (h, s, v)	(28°, 81%, 93%)
Source	The Mother of All HTML Color Charts
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

Cadmium Red
Color coordinates
Hex triplet	#E30022
sRGBB  (r, g, b)	(227, 0, 34)
CMYKH   (c, m, y, k)	(0, 100, 85, 11)
HSV       (h, s, v)	(351°, 100%, 89%)
Source	The Mother of All HTML Color Charts
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

Cadmium Green
Color coordinates
Hex triplet	#006B3C
sRGBB  (r, g, b)	(0, 107, 60)
CMYKH   (c, m, y, k)	(100, 0, 44, 58)
HSV       (h, s, v)	(154°, 100%, 42%)
Source	The Mother of All HTML Colo(u)r Charts
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

Cadmium pigments are a class of pigments that have cadmium as one of the chemical components. Most of cadmium produced worldwide is used in the production of nickel-cadmium batteries, but about half the remaining consumption, which is about 2,000 tons annually, is used to produce colored cadmium pigments. The principal pigments are a family of yellow/orange/red cadmium sulfides and sulfoselenides as well as compounds with metals other than Cd.^[1]

Artists paints

Brilliantly colored, with good permanence and tinting power, Cadmium Yellow, Cadmium Orange, and Cadmium Red are familiar artist colors, as well as being frequently employed as architectural paints, since 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 3000°C.^[2] The color-fastness or permanence of cadmium requires protection from a 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 CdSe. Depending on the S/Se ratio, one gets C.I. Pigment Orange 20 or C.I. Pigment Red 108.
• Zinc cadmium sulfide is greenish, It is a solid solution of CdS and ZnS. 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, especially orange and bright red was very troublesome, when the cadmium pigments replaced e.g. mercury sulfide (the original vermilion), the light-fastness was greatly improved,

Cadmium pigments are known for excellent lightfastness, although the lighter shades can fade in sunlight.^[3]

Safety

Cadmium orange cast iron pot

Cadmium sulfide is not very toxic (LD50 > 5000 mg/kg), despite claims otherwise that are associated with acute exposure to cadmium vapors from welding.^[1]

The cadmium pigments have been partially replaced by azo pigments, although their lightfastness is significantly inferior,^[4] although still good,^[5] and they have the advantage of both being cheaper and non-toxic. In some countries, such as Australia, consumer activists such as Michael Vernon were successful in banning the use of cadmium pigments in plastics that could be used for toy manufacture, owing to the toxicity of cadmium.

References

External links

• National Pollutant Inventory - Cadmium and compounds
• "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.