MITRA Forum Question Details

​I have sent a message to some of our moderators to get comments.

​Panic is never a good idea, but contacting the companies that make your favorite brand of paint is a good idea to be sure they are responding to the situation. All members of the ASTM committee on artists’ materials, which include the largest manufacturers, are aware of the situation, but most are not participating in the study to develop a better standard for testing lightfastness of artists’ oil, acrylic, watercolor and gouache paints.

It is always good to reach out to manufacturers and inquire about their lightfastness testing. It can only be a good thing when artists let paint manufacturers know that they care about lightfastness, the LF standards across brands, as well as transparency of testing procedures. The production of synthetic organic pigments is constantly improving and the statement about organic pigments being less lightfast than organic ones is over simplified and requires more differentiation. Artist paint manufacturers are at the mercy of pigment manufacturers, who serve much larger industries, such as the architectural paint industry and vehicle coating. Sometimes pigment manufacturers change their pigment manufacturing process without communicating that. This is why it's important that all artist paint manufacturers continuously test their paints themselves and not rely on the ASTM pigment list. Through our testing at Golden Artist Colors we discovered in 2018 that there had been changes to Hansa Yellows (PY73 and PY3) and accordingly changed the LF rating for these colors and simultaneously introduced the more stable Benzimedazolone Yellows (PY175 and PY73). Benzimedazolones are also synthetic organic pigments and they perform as LF 1 in glazes, tints and mass tone (see https://www.justpaint.org/hansa-update/). The complexity of rating the permanency of synthetic organic pigments is also well explained here: https://www.handprint.com/HP/WCL/pigmt1d.html.

In 2015 we discovered a similar issue with Dioxazine Violet (PV23), where we found in our own testing that the Dioxazine Violet pigment which we were using in our QOR watercolor line performed as LF 1 while the Dioxazine Violet pigment of two other competitors only performed as LF 3 (see https://www.justpaint.org/qor-lightfastness-testing-update/). 

Synthetic organic pigments are also not more sensitive to outdoor conditions as a general rule and the future availability of some inorganic pigments, such as cadmiums for example, is questionable especially since governments across world are implementing stricter regulatory standards and strive for more sustainability.

Given this, we do agree with Natural Pigments that the ASTM Lightfastness table needs review and we are part of the group of manufactures revising the test methods. But we disagree that artists need to limit organic pigments in their painting practice.