Making Cadmium Red — The Brilliant Cadmium Selenide Pigment of the 20th Century

Cadmium Red (cadmium sulfo-selenide, CdS₁₋ₓSeₓ) was the last great addition to the painter's palette of permanent inorganic pigments. First produced around 1910 and commercially available by 1919, it offered what no earlier red could: brilliance, opacity, permanence, and resistance to light, heat, and alkali — all in a single pigment. It replaced vermilion (mercury sulfide, toxic and prone to darkening), red lead (lead tetroxide, toxic and unstable), and the various alizarin lakes (beautiful but fugitive).

The chemistry exploits a solid-solution series between cadmium sulfide (yellow) and cadmium selenide (deep red). By varying the selenium-to-sulfur ratio, the artist can produce any hue from cadmium orange (low Se) through cadmium red light to cadmium red deep (high Se). In this blueprint we target a medium cadmium red by mixing cadmium carbonate with selenium and sulfur powders and calcining the intimate mixture at 500–600 °C in a sealed crucible.

SAFETY WARNING: This process is EXTREMELY HAZARDOUS. Cadmium compounds are toxic heavy metals classified as Group 1 carcinogens — they cause lung cancer via inhalation and accumulate in kidneys with chronic exposure. Selenium is also toxic: inhalation of selenium dust or fumes causes serious respiratory injury, and heated selenium produces a characteristic garlic-like odour that indicates dangerous exposure levels. Both cadmium and selenium fumes are released during calcination. Work OUTDOORS ONLY with a P100 respirator, full-face goggles, and leather gauntlets. Never handle cadmium or selenium with bare hands. Dispose of all wash water and by-products as hazardous waste.