How to tell if a tube of oil paint is too old?

[Pat Graham]

After a long (15+ years) health imposed break from painting I've been painting again, though with watercolors not oils, for the past 2 years. Since I still have my oil paints from long ago ( they are probably in the 20 year old bracket ) I was wondering if they were still usable and how I would be able to tell. Does anyone have any tips? I'm ready to start practicing with oils again and would like to use them instead of buying a new set if possible at this point.

Pat

[Chuck Yokota]

It seems to me that about the only thing that would make them unusable would be if air got in and the paint cured and hardened. If the paint is in the physical condition that you can use them, then they should be OK to use. After all, the pigments need to be permanent and stable so they will last on the finished painting for years or centuries.

[Julie Deane]

I've used paints that I had around for 25 years. The tubes' outsides were in bad shape, but the paint was fine.

[Pat Graham]

Thank you, Chuck and Julie. I feel better about using these paints now. When I went to do price checks on oil paints I got a real sticker shock and would hate to have to repurchase a whole new set. Yikes! Having not been in this situation before I didn't have a clue how to tell if the paints were still usable other than if the tube was hard.

[Steven Sweeney]

One thing to be mindful of is that oxidation through exposure to the atmosphere is not the only catalyst for molecular change in pigments suspended in an oil vehicle. That vegetable oils can turn rancid over time in a closed container is an indication that the substances are not inert.

I have not been able to relocate, but I will continue to search for, some long-ago read remarks about paints "cooking" or curing in the tube over extended periods of time. The product may look about the same and be physically usable, but some of the molecular change that should have gone into creating a strong paint film has already taken place. Metaphorically, it would be akin to putting small pieces of cured concrete into a wet mortar mix. The chemistry has long since taken place in those bits of concrete, which will serve only as filler in the new mix. And just as added water won't "reconstitute" the old concrete, neither will adding oil to cured paint produce a reliably long-lasting product.

I'd use the old paints for practice pieces or lay-ins, and begin putting in a supply of new, fresh paints for works in which you'll want to ensure physical integrity for a long time. In addition to the freshness of the paint, you'll have the advantage of many advances in formulations that have arrived on the scene only fairly recently.

[Claudemir Bonfim]

Once my sister-in-law gave some old tubes, some of them were still good and the paintings I made with them still didn

[Pat Graham]

That's what I was worried about, Steven, but didn't have the terminology to express it. Thank you for putting my concerns into words. These paints that appear usable will certainly be only for practice and relearning what I was taught years ago.....I'm sure I'm just a bit rusty. The good side of this is that I won't be worried about wasting 'good' paint in my experimentations and all as they will be perfect for practice.

A limited palette is a good idea as well. After reading 'Watercolor Mixing, the 12 - Hue Method' by Christopher Willard I've been quite pleased with the results of a limited palette in that medium. A painting that I have just about finished of 2 fishermen and their catch has been done using only 4 colors plus Lamp Black and I'm very happy with the way it's turning out and how the few colors unite the painting. I suppose the results would be similar with oil painting.

Bonfim, I think I'll stop complaining about the price of good oil paints here in the U.S.A.

[Steven Sweeney]

Some notes from from Winsor & Newton