Painting - How to prevent layer of dried out paint

Yesterday I opened a gallon can of oil based house primer that has been unused for several months, and it had a layer of dried out paint on top. This has occurred with any oil base paint I have used in the past. So, I'm wondering what others have done to prevent, or otherwise deal with this. What I do is use my paint mixing stick to go around the outside of the dried layer until it's free, then scoop it out and throw it away. Then I add some paint thinner to compensate for the discarded paint.

2 things you may try. If you use a bunch of paint, and you only have a bit left, pour the remainder into empty quart cans, and seal them tightly. This will help prolong the paint, as an empty (or nearly) can has plenty of space for the paint to dry in.

You may also try before sealing your can to "float" a layer of thinner in the can before sealing. This should help create a seal that will slow the drying process.

It is very important to make sure you have a good seal on the can as well. Even a pinhole size opening is enough to skin the oil.

BTW unless you are going to use it, taking the skin off will only make the rest of the paint kick over. The skin actually will help inhibit further drying.

Adding thinner to the remainder, will help thin the material, but it won't replace what you take away with the skin. It is composed of solids, drying agents, and some other goodies. The thinner has already flashed off, hence the drying.

I store old cans of paint upside down, just for this reason.

I usually add a thin layer of the appropriate reducer to the top of the paint. If the paint does skin over you probably ought to strain the paint before using.

Thanks guys for the input. I think I'll try storing the paint upside down to see how this works out.

Hello,
An ounce of prevention - -

Make sure there's nothing in the rim of the can and the lid can seal as tight as it did from the factory.
If the can is less than 2/3 full, pour it off into smaller containers if it's going to be stored for a month or more.

2/3 or more full, turn it over.


Rich <-- who's seen many a half full can turned over that appeared "full". Why? Because the skin formed anyhow. Matter of fact, I have a can of Man of War spar varnish that's in that condition in the garage right now :D

Rick E: Thanks for the input. I agree with you because it makes sense that if you turn the can upside down you're still trapping air inside the can. So, I'd expect the paint to still dry, but the layer to be at the top instead of at the bottom.

Pouring the paint into smaller containers should help since there will be less air inside: assuming a tight seal at the lid.

Ideally, it seems that if you could somehow vacuum seal the cans after use you wouldn't have this problem. Anybody ever seen anything like this, or come up with their own method: like a custom paint can with a vacuum port and a small vacuum pump to use to suck out the air?