MITRA Forum Question Details

Great, thank you.

Yes, it is the stabilizers and fillers that trouble me, for longevity. I wonder how they will behave after 60 years...

As for lightfastness, I am always certain to purchase tubes utilizing the most lightfast pigments available, and follow fat-over-lean, and other general rules. I hope things work out in the long run. As you say, mid-tier from reliable brands should be OK. I hope Van Gogh oils count as this.​

I would be the most concerned about the longevity of the support. However, stabilizers might migrate to the surface over time, creating a haze. Some brands add wax which also may present a solubility issue.

On the flip side, one company's testing claims to show that not adding driers and/or wax to pure titanium dioxide oil paint causes more problems with that pigment's paint film. Just oil + pigment isn't enough, according to what they claim they found. One of the additives that greatly improved the paint film was wax. However, a conservator here warns that wax may cause solubility problems which can impact varnishing and conservation treatments.

Most tubed oil paint has alumina stearate added as a stabilizer. Some brands use additional stabilizers and modifiers, such as hydrogenated castor oil, wax, alumina hydrate, blanc fixe, calcium carbonate, zinc oxide, et cetera. Many mid-tier brands add quite a bit of siccative. Siccatives have a varied reputation that may depend upon how much is used and which ones.​

The only way to know how the paint will perform in advance is to remove all unknowns. That means one can't purchase brands that use trade secrecy unless one wants to pay a chemistry lab for full evaluation — and buy enough of the product shortly after than to ensure that batch and reformulation changes don't change the product significantly.

Brands that give out somewhat detailed technical information at least seem more trustworthy than those that refuse to provide even pigment codes. However, it is possible to provide some information whilst still keeping important information under trade secrecy.

— SRS

Additionally, another thing that some budget and mid-tier brands may do is use sunflower oil, which shrinks the most of the common semi-drying oils during the curing process. This could cause a brittleness issue with the paint film. Linseed is the only common oil used in oil painting that doesn't shrink much. The others shrink quite a lot more, with sunflower shrinking more than poppy which shrinks more than walnut which shrinks more than safflower. None of those "alternative" oils are close to linseed's volume stability.

Companies like Grumbacher refer to oils like sunflower as providing a "soft" paint film, which I consider misleading. Many describe this as a "weak" paint film which is also misleading. What it actually is is a brittle paint film. There is nothing "soft" about it. 

To Grumbacher's credit, it is one of the few oil paint brands that uses linseed oil throughout its line. However, its whites all have zinc oxide added and it doesn't have a proper cobalt violet light (which is a rare exception pigment in that it shouldn't be ground in linseed due to the yellowing impacting the color too much).

— SRS​