Cadmas

Cadmium is similar in its properties to zinc and is found in zinc ore. In its pure state it was obtained in 1817.
Sulfur compounds of cadmium are found in nature as the mineral "grenokite" with a yellow (to orangish) hue. However, it is such a rare mineral that it has no practical use.
Cadmium sulfates were obtained artificially in the first half of the 19th century, and from then on dates its use in painting.
Dyes having cadmium sulfide in their composition are characterized by color intensity, durability and are used in all techniques except lemon-yellow shades.
They cover well, non-poisonous, resistant to alkali.

Yellow and orangish cadmium (cadmium sulfide).

They are obtained by wet and dry methods.
Wet:
A solution of cadmium salts is deposited with hydrogen sulfide. Initially, a light yellow hue is obtained, and by further action of hydrogen sulfide, an orangish hue is obtained.
Dry:
Roasting of cadmium compounds (such as cadmium carbonate) in crucibles with sulfur. In this way, only one shade - "medium" - is obtained.
All shades of cadmium obtained wet under the influence of roasting adopt the shade of cadmium obtained dry. Cadmium obtained dry takes on an orangish hue by long rubbing and pressing.
Bright cadmiums are impermanent. The most durable - orangish and red.
They are sulfur-containing products and should not be combined with copper and lead (they blacken). Cadmium yellows, which contain sulfur in the free state, are particularly sensitive to this. Cadmium yellows should also not be combined with ugrams, as they darken after a while. In other combinations - permanent.
Cadmium yellows have medium covering power and dry slowly in oil.
Orange ones hide and dry well.
Recognition:
Dissolves in dilute hydrochloric, nitric and sulfuric acids, emitting hydrogen sulfide and forming a colorless, transparent solution.
In alkalis it does not dissolve.

Cadmium red

It is among the more recent dyes (since 1912). It contains cadmium sulfide and selenium in its composition, as well as indispensable spätzle.
Light grades contain 7.6% of spat, dark grades 58%.
It is superior to yellow cadmiums in durability.
Used in all techniques, more durable than cinnabar.
In fresco it does not change tone.