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]

John, 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

 

[Jon Rista]

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.

Thanks Gord. I am aware that there is no undoing the polymerization, I was just wondering if it could be thinned in a manner that would allow it to be applied. This stuff does cure, too fast almost, but it doesn't seem to penetrate the wood much.

It sounds like two years is about the limit for this stuff. So I'll probably buy another can soon here, and use stop loss bags or bloxygen with it too.

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

Aye, my more recent approach is stop loss bags, or bloxygen. This stuff was bought over two years ago, it looks like, and I guess its just at the end of its oxygenated life. I didn't start posting on these forums, really, until late last year, and you have shared about using a neutral gas before.

 

[Jon Rista]

Oh, regarding mineral spirits. Someone mentioned "not the 'green' stuff"... The only stuff we have, I think, is effectively "green" or at least, it has no aromatic compounds. Its only the nasty aliphatic compounds, which are supposedly more "green" than real or "proper" mineral spirits with aromatic compounds in it. It doesn't really seem to be useful for anything...is this stuff not viable for thinning oils?

 

[Wyatt Holm]

I think the problem is paint thinner vs mineral spirits. Some paint thinner is mostly mineral spirits, others are water based and act more like soapy water.

 

[John K Jordan]

my more recent approach is stop loss bags, or bloxygen...and you have shared about using a neutral gas before

I've written about this too: at one time the gas in a Bloxygen can was a mixture of Nitrogen, Argon, and CO2.



At some point they switched to pure Argon. At the time they said they discovered that the CO2 could react with chemicals in certain finishes. I think they went to Argon since it's heavier that Nitrogen and even if the air in the can wasn't completely displaced, a layer of Argon could settle inside the can and still protect the finish. Years ago I had people point out I shouldn't use Nitrogen since it is lighter than air - not a real problem for me since I completely displace the air in the can. This was handy for me since I used that tank of Nitrogen for lots of things besides finishes and it was about empty. So I switched to a spare tank of Argon.

If interested, the gasses that make up most of the air we breath are
O2 (weight 32 g/mol), N2 (~28 g/mol), and Ar (~40 g/mol, monoatomic)

Reference:

Air - Composition and Molecular Weight

Dry air is a mechanical mixture of nitrogen, oxygen, argon and several other gases in minor amounts.

www.engineeringtoolbox.com

JKJ

 

[Richard Coers]

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.

It doesn’t HAVE to be mineral spirits. Naphtha works just as well.

 

[Jon Rista]

It doesn’t HAVE to be mineral spirits. Naphtha works just as well.

Sadly, odorless mineral spirits, DNA, acetone and Turpentine are the only non-water based solvents we have left in Colorado now. The rest has all been banned.

 

[Steve Tiedman]

I use Tried and True Danish oil... I keep a small amount in a glass jar. I don’t get it hot but warm enough that it thins it.

Not sure what brand you are using as some already have thinners and dryers in them. Tried and True has no additives.

Agreed on the Tried & True products.

Glass jars- grocery store, get the most disgusting version (to you) of baby food in a glass jar. Take it home and dump it. (Or get an appetizing one and eat it, we won't judge.) Clean the jar and lid. Insert your finish product in small quantities. A coffee cup full of hot water (tap, not boiling, you don't want to crack the glass jar) can serve as a double boiler to warm the oil if you desire. I did that for years (I never thought to heat it) making homemade Danish, which cures up fast when only making pens and other little stuff. Bloxygen helps, too, with any container. Some marbles in the jar will help displace the air, too.

I have hard doubts about this next idea, but if one could strain the thickened finish somehow, a paint strainer perhaps, I wonder if the thinner portion, if there would be any which has presumably not yet started to polymerize, would pass through the strainer for continued application? With Tried & True products, this is a non-issue. An opened can has a good, long shelf life. But, Bloxygen, or marbles, or similar air-displacement methods are still sound advice with T&T.

 

[Tom De Winter]

You all realize that it's much easier to advise one to throw it out than to do it yourself. Just sayin'

 

[Gordon Andrus]

Naptha is my preference for this. I was able to extend the life of some polymerized tung oil finish using it but did end up having to throw it out. I've been using my tried and true home made mixture of Linseed oil and poly varnish. It never goes bad. I've also made a paste wax by mixing it with melted bees wax and some turpentine. I keep plastic wrap on the surface of the wax in a coffee can. It does start to cure on top but remains unchanged under that layer. I'm still using a batch that was mixed up over 30 years ago. I've recently started adding some carnauba wax to these type of concoctions with great results.

 

[Richard Coers]

You all realize that it's much easier to advise one to throw it out than to do it yourself. Just sayin'

Not in my case. With enough experience it becomes common sense to not try and save $30 for fresh finish when you’ve spent hours and hours on turning and sanding. Very few turners seem to test a finish on scrap, they just experiment on a finished piece and then ask how to fix it.

 

[Wyatt Holm]

Your point is valid, however the OP did not state that he was using this finish on turnings. For all I know he is using up old finish on shovel handles, or outdoor furniture. His question was is there a way to rescue the finish. There are many things people do that are possible, but not at all practical.

 

[Jon Rista]

Not in my case. With enough experience it becomes common sense to not try and save $30 for fresh finish when you’ve spent hours and hours on turning and sanding. Very few turners seem to test a finish on scrap, they just experiment on a finished piece and then ask how to fix it.

Always good chatting with you, Richard...

I experimented first, once I realized it was turning syrupy. I had a few pieces I'd made that I didn't fully like, and actually like the nice satin sheen they ended up with. I thinned it with turpentine, which made it go on a bit easier but the later wipe-up wasn't as great.

I have been using it on one set of turned items. I do like this nice soft satin sheen that I'm getting, hence why I wanted to find a better thinner. Not sure if this satin finish is because the finish has started to polymerize more, but it isn't what I'm used to with danish oils... Its not been the easiest application, but, the oil does dry pretty quick when thinned with Turpentine. I think one more coat on these items and I'll be fully satisfied. I don't think I'll try thinning more with Turpentine, though.

I don't know what's up with these Kleen Strip Odorless Mineral Spirits, but I really hate this stuff. I tried thinning another bottle of the almost-bad Danish Oil (which, IIRC, came from a $47 can, it wasn't exactly cheap), now the stuff doesn't seem to dry at all...its been a few days, and its still sticky on this item I tested it with.

I searched for Naptha and found some on Ace Hardware's site, however when I go to the page, they won't show the add to cart button. I disabled geolocation, cleared my browser cache for the site, and tried again, and the site doesn't seem to load that page properly. I can go to other solvent pages, like Turpentine, and it loads fine... Colorado has gone nuts over VOCs and I guess they have ridiculous fines, so it seems people are extremely wary of even shipping a banned solvent to Colorado.. Really a bummer, as Naptha seemed like the best oil-based solvent/thinner we had before it was banned. I did notice that Ace Hardware apparently has mineral spirits based paint thinner for oils, varnishes, etc. I haven't seen that recently, but it is showing on their site as in-stock at local stores...maybe this is a better form of mineral spirits, and if Ace carries it, that might be better than this odorless junk.

 

[Doug Freeman]

I did notice that Ace Hardware apparently has mineral spirits based paint thinner for oils, varnishes, etc. I haven't seen that recently, but it is showing on their site as in-stock at local stores...maybe this is a better form of mineral spirits, and if Ace carries it, that might be better than this odorless junk.

I switched to paint thinner 4-5 yrs ago. It is like ms from decades ago when you really couldn’t tell them apart. The oderless ms has gotten worse over time - to reduce smell and voc’s mfr have increased the % of content of low volatility components - less smell, much longer evap time.

As for naptha, it depends on what one wants from the finish. It evaporates quickly, so the time that the finish is low viscosity is minimal, ok if doing a film finish. For a penetrating finish, the paint thinner is much better. Stays lower viscosity longer allowing more penetration.

 

[Jon Rista]

I switched to paint thinner 4-5 yrs ago. It is like ms from decades ago when you really couldn’t tell them apart. The oderless ms has gotten worse over time - to reduce smell and voc’s mfr have increased the % of content of low volatility components - less smell, much longer evap time.

As for naptha, it depends on what one wants from the finish. It evaporates quickly, so the time that the finish is low viscosity is minimal, ok if doing a film finish. For a penetrating finish, the paint thinner is much better. Stays lower viscosity longer allowing more penetration.

Picked up a can of this stuff. Klean Strip Paint Stripper "Made with Mineral Spirits" ... At least this stuff actually smells like mineral spirits! Hoping this will work better. Still going to pick up another can of Danish and some Bloxygen, but, maybe I can still use some of this old danish before its truly unusable bad.

 

[Steve Tiedman]

Paint stripper?! To thin a finish for application? Are you sure about this? Usually these are used to break down the plastic surface (the cured finish).

 

[Jon Rista]

Paint stripper?! To thin a finish for application? Are you sure about this? Usually these are used to break down the plastic surface (the cured finish).

According to the SDS, its mineral spirits, white spirits, aliphatic petrolium distillates, naphtha (primarily) and a little bit of xylene. The xylene is a tiny amount. The rest is naphtha and mineral spirits.