MITRA Forum Question Details

Hello MITRA,

I received a gift of half a dozen tubes of pigment-rich professional paint with seemingly no strange fillers. However, two tubes have questionable pigments: PY3 and PR112. I would feel bad not finding a use for them, so I wonder if the suggestions from this post could apply to oils.

From https://www.artcons.udel.edu/mitra/forums/question?QID=776:

“If you mix a small amount of Gamblin Etching Ink Yellow Ochre (PY43), you might increase lightfastness (Iron oxides are used with an organic pigment in the paint industries). Of course, it will affect the chroma and lightness of Hansa Yellow Light (PY3).”

I also found the assertion that “adding Iron aids in increasing lightfastness for fabric dyes” at https://botanicalcolors.com/botanical-colors-how-tos/how-to-use-iron-powder-ferrous-sulfate/.

Handprint.com lists PY3 + PY42 (aureolin [hue], Holbein, in watercolor) as the most satisfactory PY3 in the listed lightfast tests (https://www.handprint.com/HP/WCL/waterfs.html). 

If you feel this tactic could work with oil paint, could the protective measure of “adding iron,” perhaps in a 1:1 ratio, also work with Napthol Red PR112 using Red Iron Oxide PR101? Or would I just have the ultimate end result of pure Red Iron Oxide after 50 years?

Also, does anyone know if PY3 ever stabilizes in its color after light exposure? 

I see it darkens and browns, but does it stabilize into a greenish-brownish dark yellow after a set amount of months or years and then remain that way, or does this process last indefinitely, leaving a strange dark green-brown after 70+ years? If that’s the case and PY3 is rather useless as a yellow in the longer term, maybe the safest way would be to use it as an "extender" or sorts for dark brown shades, or perhaps a dark Chrome Oxide Green?

Thank you in advance for any information you could provide.