Cadmium/Selenium colours

2210, 2215, 2840, 2850 & 2880 are cadmium/selenium colours. They chemically react with copper and silver and turn opaque. They will remain transparent on gilding metal, and properly prepared high karat gold, and over a clear or opaque first coat for a limited number of firings. They will darken with prolonged exposure to heat. They are best used over another enamel and/or gold foil.