What is the best way to store oil paint?

August 3, 2005 1:38 PM

Does storing a half-used can of oil paint upsidedown *really* work to prevent a skin from forming? I've also read recommendations for a small quantity of mineral spirits to be poured on top. (Which I did even try before having read it; I had marginal success but it was not long term. Anyway, I would think the mineral spirits would eventually evaoprate just as the solvents in the paint must.)

For what's it's worth, I am completely taken with storing my brushes in linseed oil. I've left them suspended in jars of linseed oil for years and the brush performs as good as new with each extration. But back to the paint: while there is oxygen in the paint can, storing it upsidedown is assurance against further air-exchanges. Is this why the upsidedown method works (if it really does work)?

posted by Dick Paris to Home & Garden (13 answers total)

Several ideas at Popular Mechanics include the upside-down trick, blow into the can, pour in a layer of solvent, and wax paper in the can.
posted by badger_flammable at 2:02 PM on August 3, 2005

Very timely. I just read this yesterday on Tricks of the trade:

Before resealing a can of paint, blow one deep breath into the can and close it quickly. You'll fill it with carbon dioxide, which will keep the paint from oxidizing prevent it from developing the "skin" that paint gets when it sits a while.

I guess this doesn't answer your question, since I don't know if the upside down thing works.
posted by bondcliff at 2:03 PM on August 3, 2005

When I worked for a painter eons ago, he'd pour in a thin layer of linseed oil, which wouldn't evaporate as readily. Next morning, just stir it into the paint and go at it. Painting, that is....
posted by banjomensch at 2:30 PM on August 3, 2005

I have trouble believing in the blow-into-the-can one... there IS oxygen in your breath when you exhale... I mean, how do you think CPR works?!
posted by IndigoRain at 3:13 PM on August 3, 2005

The upside-down can trick works because the skin still forms, but when you turn the can back up to open it, it's on the bottom, not the top...
posted by benzo8 at 3:30 PM on August 3, 2005

Breathing into the can may or may not be effective, but there is a product designed to use the same general idea, replacing breath with inert gas: Bloxygen. They claim 75 uses from a $9 can.
posted by Quinbus Flestrin at 4:02 PM on August 3, 2005

The B part of CPR works by stimulating the lungs to resume functioning, not by forcing oxygen through them.
posted by yclipse at 4:18 PM on August 3, 2005

Um, really? According to my CPR training: The atmosphere contains ~20% oxygen; exhaled breath contains ~15%. It is rare for CPR to actually stimulate your heart to start beating again; its main purpose is to keep you alive (by getting oxygenated blood to your brain) until you can be defibrillated.

/derail
posted by expialidocious at 4:50 PM on August 3, 2005

Breathing into the can is bogus. There is a lot of oxygen left in your breath when you exhale. The miniscule amount of CO2 isn't going to make a difference.

I do upside down. For starters, there's only so much drying-out the paint can do when it has no ability to "respire" through the lid seal and a limited volume of air. Upside down with linseed oil might work especially well.
posted by five fresh fish at 4:54 PM on August 3, 2005

The day before yesterday, I capped a half-full quart of varnish. Yesterday, I opened it to find a skin. I pulled the skin off and used some of the varnish, and then, when done, I did the breathing-into-the-can trick and closed the can. Today, after around the same amount of time elapsed, I opened the can and there was no skin.

Yeah, it's one time, but hey - no skin!
posted by tomierna at 6:07 PM on August 3, 2005

I guess it is remotely possible that the humidity of the breath somehow contributes to an improved lid seal...

As for the breath chemistry issue. If you inhale 20% O2 and you exhale 15% O2 then you must also exhale 5% CO2 to maintain steady state (the carbon comes from your food). That is a very significant CO2 increase compared to the atmosphere.
posted by Chuckles at 10:53 PM on August 3, 2005

Okay, call me an idiot, you are also making H2O as you break down your hydrocarbon diet. (I should probably stick to topics I know :P) I still think exhaled breath will have a very significant increase in CO2, but maybe only half as much as I said (about 2%).

Sorry!
posted by Chuckles at 10:59 PM on August 3, 2005

Benzo is right. It only makes sense that a skin prolly does form while the can is upside down, but when the can is turned right side up the skin is at the bottom.
posted by wsg at 12:19 AM on August 4, 2005