Extending the shelf life of varnishes and oils

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neb

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#237979 27-Jun-2018 17:26

Anyone who's worked with various varnishes and oils knows that they have a limited shelf life once opened, and the more air there is in the container, the quicker they degrade (cure/react/polymerise/whatever the mechanism happens to be). In the US you can get products like Bloxygen which spray a layer of argon gas into the container to protect the contents from oxygen, but over here if you don't have access to a MIG welder or similar as an argon source you're mostly out of luck.

A few days ago I was looking at an air duster and noticed that, despite its name, it's actually a tetraflouroethane (a.k.a. R-134a) duster. Like argon, R134a is denser than air so should form a blanket over the top of the oil/varnish/whatever to slow down curing. I've just filled a nearly-empty bottle of BLO, for which the reaction with air is quite visible, with R-134a, I'll report back in a week or so if further curing has occurred, but apart from that it looks like you can now get a cheap, and above all locally available, Bloxygen substitute to extend the shelf life of your varnishes and oils.

mcraenz

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#2045771 28-Jun-2018 21:21

Thanks for the tip!

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#2045777 28-Jun-2018 21:59

Nice!

neb

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#2052348 9-Jul-2018 23:49

An update on this, here's what it looks like after a few days:

This effect is far more severe than leaving air in there would do, and far quicker too, so I'm guessing the R134a is being absorbed by the BLO? I've refilled it twice with more R134a and it's still creating this vaccuum effect in the bottle (good thing it's plastic), so the air is being displaced but there's an unexpected interaction between the BLO and the R134a. I'll keep refilling with R134a to see how long it goes on for, at some point I'll try it with generic polyurethane varnish to see if there's any interaction there.

kiwigander

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#2052352 10-Jul-2018 00:06

If the limiting factor of the shelf life of varnishes and oils is exposure to air (specifically, I would imagine, oxygen), then I propose a much lower tech solution.

Get a bag of marbles, if they'll fit through the neck of your container - glass beads if marbles are too big - and every time you drain off some of the varnish or oil, top up the volume with marbles to drive all the air out of the container.

It may sound daft, but that's what we used to do in the days of chemical photography when expensive developing solutions would tend to go off because of the oxygen in a half-empty bottle.

neb

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#2052357 10-Jul-2018 00:27

kiwigander:
Get a bag of marbles, if they'll fit through the neck of your container - glass beads if marbles are too big - and every time you drain off some of the varnish or oil, top up the volume with marbles to drive all the air out of the container.

Most of the substances are quite viscous, think something like treacle, so you'd end up with most of it stuck to the marbles. Also I'm not sure whether you'd want to disperse something like polyurethane like that, it cures from the surface down so after the initial curing you get a protective skin forming that slows down the curing of the main body. Spreading it out thinly over marbles will probably mess up this self-protecting behaviour.

neb

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#2068886 6-Aug-2018 17:33

neb: An update on this, here's what it looks like after a few days.

An update on the update: After two more refills of R-134a, it's now fine, the bottle is firmly filled with it and there's been no further change in a month, and no degradation in the BLO. So it just seems that it's very soluble in BLO, all you need to do is saturate the oil and then it'll work as expected.

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debo

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#2068917 6-Aug-2018 19:32

Have you tried LPG. Its heavier than air and most people will already have it. Just remove the hose off the BBQ.

Buster

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#2068950 6-Aug-2018 20:24

Have you tried storing the part used container upside down. When the air rises it is rising towards the bottom of the container. If a skin forms at least it isn't near the lid the next time you open the container.

neb

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#2069427 7-Aug-2018 16:57

Buster:
Have you tried storing the part used container upside down. When the air rises it is rising towards the bottom of the container. If a skin forms at least it isn't near the lid the next time you open the container.

Yeah, that's an old trick, but it relies on the seal being 100% tight so you don't get any leakage, is difficult to do for anything other than a flat-topped can, and still exposes the material to the air in the can. The nice thing with the gas filler is that there's no air exposure, and you can store the material as you normally do.