A Vacuum Experiment with Paint Jars

If you have read my Gimme Air page, you know that I have a small vacuum pump. Since I no longer use it for an airbrush compressor, it has been sitting idle. The other day, It occurred to me that it might be fun to play with. So, I connected it to a jar and created a little vacuum chamber.

Note: The jar is pretty heavy glass, and the first time I evacuated it I had a towel over it and bounced it around a bit. I wouldn't try this with a larger or more fragile glass container.

Inside the vacuum jar, is a Testors Modelmaster paint bottle. And, inside the paint bottle is a small marshmallow.

If I barely tighten the paint bottle lid and turn the pump on, the marshmallow will expand to about twice its original size. What I have found is, if the paint bottle lid has a good seal, the marshmallow will remain big even when I release the vacuum. Then, if I loosen the bottle cap, there is a little pop, and the marshmallow immediately shrinks to less than its normal size.

This reminds me of when my Mom used to can stuff. The canning jar lids were two pieces. One was a disk with a rubber gasket that sat on the jar, and the other was a ring to tighten it down. With the lids on loose, the jar and its contents were put in boiling water for a period of time. The jars filled with steam. When they were cooled, the steam condensed and the resulting vacuum drew the lid down tight. It would stay on even without the ring. I think the same thing is happening in my little chamber.

Some of my empty bottles don't have a good seal, and the marshmallow shrinks as soon as the vacuum is released. I don't think these would be the best choice to store paint or solvents. I have been trying to find something that will replace the cap liner and give a good seal. I have some heavy vinyl sheet that's about 1/16 inch thick, that seems to work, but I'm still looking for something better. If you have any suggestions, please pass them along.

I think I will start doing this when I put my paints away. If nothing else, there shouldn't be any oxygen left in the bottle for the paint to react with.

I don't expect anybody to run out and buy a vacuum pump, so this is probably of no practical value to you. But, I thought you might be interested. And, maybe it will spark an idea in someone who will come up with something better.

Postscript

I got a coupon from Harbor Freight for the transfer pump on the right. It was marked down from $12.99 to $3.99. Inside the package are adapters and a smaller hose that fits my jar. I thought it might be a good alternative for the vacuum pump, so I picked one up. Wellll, not quite. It does pull a vacuum and cause the marshmallow to expand, but not as much as the electric pump. And, as soon as you stop pumping, the vacuum leaks away. I don't generally have a need to siphon gas or oil, but maybe I can use it to pump up balls or our Granddaughter's bike tires.Post PostscriptThis thing may be OK for some liquids, but it's a lousy air pump. The check valve leaks so much that it's useless for a bike tire or a ball.Home Back to Paint Bottle Hygiene