Preserving Leftover Paints and Varnishes

Posted by at 12:04PM - Comments: (7)

Bloxygen displaces air in the container with inert argon gas.

So you carried out an exhaustive spring maintenance this year and are now left with several cans of very expensive marine varnishes, bottom-paints, and other marine maintenance products—some opened, some untouched—that you don’t want to go bad. What to do?

Stored in a dry place at room temperature, an unopened container of most of the varnishes and wood finishes will last anywhere from three to five years. However, some unlined metal cans will corrode surprisingly fast, so protecting the can with a corrosion preventative may help extend the product’s life. Keep in mind that even though a product appears a slightly different color after some time in the can, it may be fine once applied. It’s good to apply it to a test patch before throwing out a batch.

Once a container is opened, a multi-year shelf life is not guaranteed, but here are things to preserve the product for another season:

• Store it in a cool, dry place with the cap tightly sealed. (Some woodworkers suggest storing cans upside-down to better ensure a tight seal.)

• When using the product, avoid introducing contaminants into the can by pre-mixing and then pouring it into another pot for application.

• Meticulously clean the lid and lip before closing. The catalyst containers for some two-part finishes can cement shut.

• Reduce the amount of air left in the can. You can put the remains in a smaller can (available at most paint stores). We've also heard of people putting marbles in the can to raise the level of the varnish back to the top.

In addition to the above tips, a few readers have recommended pumping half empty cans of varnish with a product called Bloxygen. Bloxygen contains pure argon, a naturally-occurring gas used for welding and in packaging bagged foods like potato chips. The gas displaces oxygen in the container container, helping to preserve the contents.

A .40-ounce can is available at various internet retailers for about $10. When ours came in the mail, it was so light, we were certain we’d been sold an empty can of "Florida sunshine." However, according to the maker, each can is good for 75 quarts. Pumping the stuff into the coating’s can requires no fancy handwork, but make sure the can’s rim and lid are clean and still seal tightly. When you spray, avoid spraying directly into the varnish or paint because this can cause it to splash out.

Does it work? In 2008, we counted several cans of marine varnish left over from our test of wood coatings. As is our policy, we ended up donating most of those to local charity (the Sarasota Youth Sailing Program is one of our current partners), but we kept a few for follow-up testing. This year, almost four years later, I opened up a half-empty can of Epiphanes Rapid Clear that we’d sealed with Bloxygen, and I couldn’t tell the difference from the original in the way it looked, smelled, or applied.

The same, however, couldn’t be said of all the varnishes we protected. The two-parts seemed the most vulnerable, but this may have been due to some negligence on our part. Of the eight cans we sealed, five seemed in good shape, although I have not yet applied them all.

Bottom line: Based on our experience, Bloxygen is worth using for those who have multiple cans of expensive coatings to protect, but success isn’t assured with all products, particularly two-part wood finishes.



Comments (7)

Bloxygen has an animated video that should explain it all.

Search YouTube for Bloxygen Animation or see our website.

Posted by: Bloxygen | June 28, 2016 3:07 PM    Report this comment

StopLossBags are another method, they hold one liter. Dispense what you need then squeeze out any bubble before tightening the cap.

Posted by: tschrunk | November 15, 2014 10:13 AM    Report this comment

Wow, a four year test is the real deal. We're glad Bloxygen worked so well. Perhaps some of the problems with the two part finishes was some cross contamination; you must be very careful about that. We have updated our website with a new "best practice" video that may help in this area. We cannot recommend using propane in your is a highly reactive chemical. The opposite of heavy, inert argon. Be careful folks. for more.

Posted by: Bloxygen | November 1, 2013 3:14 PM    Report this comment

Darrell is incorrect about argon being "highly combustible. It is inert, and not combustible at all. It is used in welding as a shielding gas to keep oxygen from the active weld.

Posted by: Steven C | September 8, 2012 10:48 AM    Report this comment

Thanks for the comment Guy. Even in small quantities, I'd not want to use such a highly combustible gas for this purpose . . . certainly not on board. . . . In the garden shed next to the frightening sculpture my wife picked up New Mexico perhaps.

Posted by: Darrell | September 7, 2012 9:30 AM    Report this comment

Propane also works. It's heavier than air which makes it easy to fill the can.

Posted by: Guy J | September 7, 2012 8:26 AM    Report this comment

Try a shot of propane into the can. Works, and costs less.

Posted by: Peter G | September 5, 2012 6:49 PM    Report this comment

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