In the Facebook group, there are passing references to Mars Orange and Pyrolle Orange, but not enough information for an entry on this site.
The qualities of specific pigments can vary from manufacturer to manufacturer. In general cadmium orange is praised as an opaque pigment with high tinting power, excellent lightfastness and average drying time. Michael Hardings Paints describe their cadmium orange as being low in oil content. Other manufacturers indicate that their orange is high in oil content.
The Winsor & Newton website has an article on the history of orange: “Colour Story: Cadmium Orange”. On the origins of this colour: “Orange itself is a complex colour. In the natural world, it shares its name with the citrus fruit brought to Europe from Asia in the late 15th and early 16th century, referred to in Sanskrit as naranga—which became naranja in Spanish and laranja in Portuguese. In English, from the Old French and Anglo-Saxon orange, it was known only as ‘red-yellow’ until the arrival of this fruit.”
Pigment Number: PO20
PO 20 can appear to be different hues depending on how it’s manufactured. Virgil uses Rublev’s Cadmium Orange because he prefers paints made without stabilizers.
Cadmium orange is probably the best choice for high chroma. I haven’t yet tested pyrrole orange, so cannot say with certainty whether it will prove to be as lightfast as pyrrole red.
Cadmium orange is sometimes a mixed color, but there is a very nice single pigment cad orange (PO 20) that some manufacturers put out (Natural Pigments, Langridge, Art Spectrum). Winsor & Newton’s Cadmium Orange is not a single pigment shade. (PO20. PR108)
Re: Cadmium-free orange. Winsor & Newton offers a cadmium-free yellow, orange and red. Their cadmium-free yellows are bound with safflower oil, and the orange and reds with linseed oil. The pigments aren’t listed on the WN web site, but their lightfastness rating of A is a step down from AA, indicating that they aren’t as lightfast as the real cadmium yellows, oranges and reds.
Re: Drying Time. A Facebook user asked why their underpainting in orange did not dry quickly. Virgil responded: “Your choice of cadmium orange in underpainting is one reason for the slow drying. Even as an alkyd, cadmium orange is not a fast dryer, and it’s not really lean enough to be ideal as an underpainting paint. Having wiped most of it off, you might be all right, but I’d recommend wiping the surface with a dry white cloth to see how much, if any, paint ends up on the cloth, to determine whether the remainder is underbound and could interfere with the adhesion of the next layer to the ground. If all is well, then you’re safe for a new beginning, but I’d look for a way to leave cadmium orange out of it until perhaps the final layer. A synthetic iron oxide (Mars) color would be a better choice, mixed with lead white if you can get it.”
On the safety of using cadmium paints:
If your objection to cadmiums is based on the belief that they’re toxic, it might interest you to know that the cadmium compounds in these oil paints are not sufficiently bioavailable to present a significant health hazard. This was the upshot of ASTM’s argument in convincing US Congress not to ban cadmium paints back around 1990. It was demonstrated that they are not water-soluble, so cannot poison groundwater, and they aren’t a health hazard because our bodies can’t absorb them. They aren’t pure cadmium. It’s still prudent to not be sloppy or careless in handling oil paints, of course.
For an overview of the cadmiums see, Pigment of the Ages: Cadmium Yellow/Red
The Color of Art Pigment Database: Cadmium Orange P20. Cadmium Orange is a color modification of cadmium sulphide (Cadmium Yellow). Cadmium pigments are nearly insoluble in water, limiting their potential toxicity. They are carefully engineered to meet extremely low solubility limits.
“A risk assessment of these products conducted by the EU concluded that these products offer no significant hazard to either human health or to the environment.”