Rescuing Danish Oil that's starting to polymerize in its bottles?

[Jon Rista]

I have some Danish oil I bought a couple of years ago or so. This was before I started using stop-loss bags for everything, at the time, I was distributing finishes into small bottles that could be used up in quickly, and keeping them sealed until use. That worked great for a while. Its been over two years, now, though, since I first distributed. I still have a decent amount, maybe a bit less than half a can, and these can's aren't cheap anymore. The oil reacted with the little oxygen in the bottles, and then sucked in more. Each of them has been pinched tight, and the oil is starting to get a little syrupy. It still produces a beautiful finish, but, it is becoming harder to use.

I am wondering if there is a way to rescue these remaining bottles, perhaps with some kind of thinner? I tried turpentine, which I have used as a thinner for Danish oil in the past. It does thin it out, but, it also seems to result in it actually curing on the wood faster, and I basically have no working time. I wipe it on, and if I don't wipe off "the excess" right away, then it becomes more sticky and it gets harder to wipe off the excess, but, it also had so little time to soak in, its not necessarily all excess, per-se. I'm wondering if there is a way to thin this stuff in a manner that will extend the open time a bit, allow the oil to soak into the wood more, before I have to wipe off the excess?

I live in Colorado, so, I guess, our options are limited. About the only thinners I think I can get ahold of are:

* DNA
* Isopropyl (91%)
* Turpentine
* Odorless Mineral Spirits
* Acetone
* Lacquer Thinner


Actually, I think that is all we have that might possibly work to thin oils... I'm not even sure about lacquer thinner...and don't think acetone is viable either. Our mineral spirits, STINK to high heavens, and I don't know that they actually work real well as a solvent of any kind, but, I do have a ton of it.

 

[Wyatt Holm]

I would use mineral spirits.

 

[Richard Coers]

I’d buy new. Who knows if it will dry when used now. No time to pinch pennies when all the labor has been put into the project. Finishes don’t last indefinitely on the shelf.

 

[Doug Freeman]

Regular, not green, mineral spirits or paint thinner.

 

[Kevin Jenness]

Toss it.

 

[Fred Hargis]

You can try the MS and see what happens, if it doesn't work you'll have to dispose of it.

 

[Mark Jundanian]

Doug, I'm not a chemist, but I don't think the chemical reaction of polymerization can be reversed just by adding solvent. The apparent viscosity of the material may change, but it's still going to be polymerized.

 

[Gord Cameron]

The correct thinner is mineral spirits, but in advising that you toss what you have and buy a new can, I echo Richard's two points:

On the technical side, it is difficult to predict whether and how the finish would cure after you have added the mineral spirits. Though I wouldn't take the chance, a straight poly or other varnish might be rescued this way, but Danish oil usually contains polymerized linseed oil, and if the thick consistency of your Danish oil has come about from the (further) polymerization of that oil, it will not be reversed by the addition of mineral spirits, and both the appearance and curing behaviour of the finish will be affected.

But for me, the stronger point is "why take the risk?" Once we have put all the time and effort into making a piece, why try to save a few dollars on old finish, with the risk that it will have a compromised finish or actually be a mess? We can save money even in our expensive hobby, but for me, if there is one place where I don't pinch pennies, it is finishing.

 

[David Wyke]

I use Tried and True Danish oil. If I want to thin it down I just use a little heat. I will sit it in the sun for a while or use a heat gun to warm the oil. It thins the viscosity of the oil, allows it to penetrate and flow better, and doesn’t change the curing time. I keep a small amount in a glass jar. I don’t get it hot but warm enough that it thins it.
I do the same with rattle can lacquer before spraying.
Not sure what brand you are using as some already have thinners and dryers in them. Tried and True has no additives.

 

[Ed Sandle]

I use a lot of Watco Danish oil, and have found two years is about the limit for me at least. After that it seems to take longer to cure. I usually throw a couple of 1/2" bolt nuts in the new qt can when I get one and that helps, I think, to stir it up when shaking before using.
Just bought a new can the other day, and yes, it's getting expensive, but really a nothing when you compare it to everything else. $10 a year is fine by me.
David, I'll have to look for some of that Tried and True Danish oil to try and compare.

 

[John K Jordan]

In my experience, once "danish" oil begin so set up it's not worth saving. I throw it out.

That said, I'll repeat what I've mentioned here before: I treat open cans/bottles of finishes to replace the air with inert gas. The commercial product Bloxygen works well and I used it long ago. It contains only inert gas (argon).

Now I keep a pressurized cylinder of either nitrogen or argon in the shop. I also use it on opened bottles of CA glue since I found the better manufacturers do that before sealing the bottle for storing and shipping. This works extremely well.

I have good proof that this method works. TruOil is one of the worst - I suspect it is sold in small bottles since they expect it to go bad quickly once opened. I have some unopened bottles that are good, but the proof is in one larger bottle I opened and used while making handles for horse-riders crops - wood that, like gunstocks, will be eposed to sun, rain, hands, etc. I displaced the air in this bottle in Nov 2015 when I last used it and it's still good today.

Or do what Frank Penta and others do: mix up your own "danish" oil: his recipe was 1/3 poly, 1/3 BLO, and 1/3 mineral spirits. We've been using some sapele platters finish with the "danish" oil he mixed up over 10 years go.

I'd displace the air in the gallon can of BLO and the polyurethane (1-part, 2-parts, or water-based types) before sealing the lid. Other things like the bags, jar full of marbles, etc should work but the inert gas is my choice.

JKJ