MITRA Forum Question Details

Combining organic and inorganic pigments in paint is a strategy recommended by coatings experts to offset the potential light-induced fading and weathering of organic pigments with inorganic pigments. Organic pigments offer higher color saturation while lowering cost of coatings. Inorganic pigments typically have better weatherability.

While this is a good strategy for commercial coatings, such as architectural coatings, implementing such a strategy in commercial artists’ paints is impractical.

Artists can create these types of mixtures, but it does require advanced knowledge of the compatibility of individual organic and inorganic pigments, many of which are presently not known, and must be tested.

Some organic pigments may have sufficient lightfastness, such as arylide yellow (PY74) and pyrrole red (PR254), on their own in fine art. The issue for architectural coatings is that coatings must also have very good weatherability, which pigments used in indoor applications do not require.

Just back from a vacation from the internet for the holiday here in North America.

I believe that George is relaying that recent preliminary test have shown that certain contemporary pigments perform differently when mixed with different pigments (eg a certain color may have a particular lightfastness rating when mixed with one color, and another when mixed with a different color). This is all very preliminary and may not turn out to be a big deal. Far more testing is needed to assess this phenomenon.

As to the central point of your question, it is very unlikely that adding a stable inorganic pigment to a less than stable organic pigment would drastically protect the fugitive component. It is true that some pigments do absorb UV, zinc white is one, which is why it was/is a major component in some sunscreens. This does not mean that the benefit would render the mixture lightfast, only an improvement.  The organic colorant would still receive the energy from the light. As a corollary, it was very common practice in the 17th century to mix yellow lake pigments with azurite or even lapis ultramarine to create rich greens. The yellows eventually faded leaving blue leaves and foliage. Even as late as Edward Hopper we see green made from stable blues and fugitive modern organic yellows that have faded resulting in blue trees. Cost and opacity are probably far bigger factors for industry. Most, but not all, of the brilliant organic pigments today are very transparent (Pyrrole Red is one of the exceptions, and it is very robust). The super-saturated organic colors are also often far more expensive than their inorganic counterparts (like everything there are exceptions to this, and the intensity of many organic pigments means that far less needs to be added to a mixture to create a brilliant effect).

UV absorbers and scavengers added to varnish would likely offer much more protection.  They would never be added to oil paint where they would inhibit proper oxidation.

Others will probably add other caveats to these pronouncements and some may even contradict a point or two, but that is why this is a forum and not a sacred text 😉

​It could not hurt :)