Preserving Leftover Paints and Varnishes

Posted by at 12:04PM - Comments: (4)

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 showed no sign of deterioration.

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 (4)

A quick look at the periodic table shows that Argon is heavier than air and is a noble gas. It has an atomic weight of 40 whereas the atomic weights of oxygen and nitrogen are 16 and 14, respectively. When Bloxygen is sprayed into the can, the argon naturally sinks beneath the oxygen and nitrogen within the air overlying the liquid in the can. Old timers have told me to exhale in a can of varnish before sealing. Breath contains excess CO2 (relative to air) and CO2 has an atomic weight of 44, so presumably, the CO2 displaces the air in a similar way to the argon. However, the advantage of argon is that it is a noble gas and is thus chemically inert.

Posted by: Winsome | April 28, 2017 2:02 PM    Report this comment

Thank you for the review! Bloxygen has been helping the finishing community for over 20 years now. We have some great videos. Just search for "bloxygen videos" on YouTube.

If you have any questions, just drop us a line. I bought my first sailboat at age 10 and have sailed ever since.

Posted by: BloxygenBoy | April 27, 2017 11:52 AM    Report this comment

I have worked with all kinds of paints and Varnish's for many, many years, from my youth as a deckhand on the Great Lakes ore boats, a midlife stint painting houses,and for the last 26 yrs. on yachts of the Pacific NW. For Varnish and enamels ( including Brightside, etc.) any kind of mineral spirits based paint, when you are finished with a can and plan to put it on the shelve for a spell, pour a thin layer of solvent on top and then seal the can, try not to shake it up, and put it on the shelve. It will be just like new for years to come.

Posted by: BrightWork NW | April 27, 2017 11:21 AM    Report this comment

For varnish I just put a tablespoon (more or less) in the quart can before sealing it up. After sealing the can I turn it upside down for half a minute or so, to help seal the lid. After several uses I end up with varnish stalactite on the top of the can. NOTE: the varnish I use says "contains petroleum distillates" on the label.

For my bottom paint I buy some quart can and decant the paint into them. My bottom paint is water based so I follow the same procedure but with water.

Posted by: mark maugle | April 27, 2017 9:09 AM    Report this comment

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