PY139 is a single-pigment yellow-orange option, similar to Isoindolinone Yellow Deep (PY110) or Hansa Yellow Deep (PY65). (Those are the comparisons along the bottom, along with Benzimida Orange.) It is nontoxic, moderately lightfast, and available from three manufacturers that I could find: MaimeriBlu’s Gamboge Hue (above), Daniel Smith’s Isoindoline Yellow, and Roman Szmal’s Permanent Yellow.
Experiment Results
Hue: I found this pigment to be slightly more muted than my other yellow-oranges, although not as much so as Raw Sienna or similar.
Gradient: Very smooth gradient. A bit weak and streaky in masstone, though I commonly find these issues with MaimeriBlu colors, so may not be pigment-related.
Transparency: Transparent.
What Others Say
“…worth investigating if you want a transparent warm yellow for your palette (it is almost exactly the same hue and value as Daniel Smith cadmium yellow deep).”
Bruce MacEvoy, handprint.com
The color is not at all suitable for mixtures in the green direction if you strive for a reasonably clear mixture, green colors mixed with isoindoline yellow and some blue color all become very cloudy. The color is much better suited to mixtures with different red and other yellow colors but it is beautiful as it is, unmixed.
Erik Lundgren
My Review of PY139
This is an acceptable yellow-orange but it didn’t wow me. I don’t see a real reason to choose it over the more common yellow-orange options of PY110 or PY65.
On my palette? No.
Favorite alternative: Holbein Isonindolinone Yellow Deep (PY110)
Perhaps try a different brand. One can’t really make a conclusion about a pigment based on one brand’s sample. Cobalt violets (the “light” types) are an excellent example, especially in oils. So many brands cut the pigment with filler to save money that one can assume that those pigments are all weak. However, when one tries a concentrated brand like Prodigal Sons, one sees the difference. Another thing with inorganic pigments is that not every factory that creates them makes them identically. There can be variations in a pigment code. For instance, PY83 comes in an opaque form and a transparent form.
I had a typo in my message. I meant to type “organic” pigments, not inorganic.