I currently am finishing a table(red oak and Norway maple) with tung oil (hope’s 100%), but seem to be having some trouble getting the desired results. For one, the oil seems to take far too long to dry. I soak the wood and then am careful to wipe the excess off but after a couple days the wood still does not seem to dry. I’ve been doing this on very warm dry days as well. I’m basically following a recently FWW article on oil/wax finishes. Could the tung oil be bad? Does tung oil go bad like a varnish? Should I be diluting the oil with mineral spirits? Why would diluting matter? It’s a small table, well 30 x 48.
Also when I sand between coats, the sand paper is easily clogged. Wet sanding seems to be more successful, but although the wood is dry to the touch, the clogging suggests otherwise. Is polymerized tung oil what I should be using?
Lastly, the maple for this table is snow white before finishing, but after a coat I can see a yellow hue come into the wood. I really don’t want this. I know linseed oil does this, but was under the impression tung would not. What will yellow more, tung oil or the cheap minwax poly that’s so hip now. I don’t want to use a poly for aesthetic reasons, but I really don’t want to loose the beauty of the maple.
Thanks
Replies
all oil products will yellow. all of them. that's just oil. if you want a water white finish it has to be a waterborne finish, which you probably don't want.
as for dry time, you are using raw oil. granted tung oil is not linseed oil, but it still should take a week between coats for raw oil. it may be dry to the touch sooner, but the piece will start to look greasy if you try to apply it sooner.
oils are not really meant to be applied raw. you have to mix up some sort of varnish. try mixing a quart of varnish that is 2 parts oil, 1 part naphtha (NOT mineral spirits, trps, paint thinner, but vm&p naphtha) plus a capful of japan drier. with this mix you should be able to recoat after about 4 days.
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If you are using raw tung oil, you need to add some Japan drier in order to reduce the drying time. Be sure to check what kind of tung oil you have. Something like Formby's tung oil is closer to a varnish than a raw oil, and will not need any drier added to it. Polymerized tung oil should not need driers, but you can always add a little to speed drying.
Sanding: sanding (300-400 grit) while wet for the first application or two will fill pores nicely, but this is probably not needed on maple. And with maple, any oil will give it something of a darker color, though BLO is the worst. Sanding dried oil that should have been wiped off is guaranteed to give you a clogged mess, even with stearated sandpaper. With some woods (like bubinga), doing a dry sanding after not wiping down the oil is a great way to fill the pores, even if it is really messy. It gives a great color and glass smooth finish.
Mixing: adding spirits, turpentine, naphtha or other thinner will help the oil penetrate the wood -- initially. For later coats it just reduces the amount of oil you are applying, and is not needed. You can mix oils with varnishes (which themselves are polymerized oils) as well. It's a matter of preference. I disagree with the previous poster--you do not need to only use naphtha. Naphtha is very volatile and while this means it promotes drying, it doesn't allow as much penetration, which is why you are thinning the oil in the first place. I use MS or turpentine and they work just fine.
An oil/varnish mix is a good finish for maple, though you will color the wood some. BLO colors it too much, and besides, BLO stinks. I am phasing out it's use after this last batch is gone.
Good luck and stick with it. Oil/Varnish finishes are nice, durable and easy to apply.
Paul,
Japan drier (metal drier) will not accelerate tung oil's polymerization. Drier will accelerate linseed oil. Tung needs to be heat-treated to start the process (partial polymerization), then it will polymerize much more rapidly than raw oil.Rich
Don't ever learn anything new. Rather than give you satisfaction that you know more than you did, it will only confirm you know less than you thought by opening horizons to things of which you had never dreamt and which you now must explore.
You sure about that? BLO and Tung oil probably undergo a chemically similar reaction when they polymerize. Therefore I would expect that what catalyzes one will catalyze the other. Guess I should look up the reactions and see for myself. Do you know what they are? I suspect that both are auto-oxidation reactions of conjugated sterates. If so, a metal drier will catalyze the oxidation for Tung oil, too. But I'll have to look it up to be sure...Recommending the use of "Hide Signatures" option under "My Preferences" since 2005
"You sure about that?"
Yup.
Rich
Hmmm...
Why are you so sure? I did a quick look into the differences between linseed and tung oils, and it sure looked like metal driers would catalyze the polymerization in tung oil, too. I'll have to look more into. I do have a PhD in Biochemistry, so I feel confident in understanding the chemistry of these reactions. But I haven't scoped out everything on the differences between polymerization of these two oils.
Again, why are you so sure? What's the reason that I haven't found yet, if there is one?
PaulRecommending the use of "Hide Signatures" option under "My Preferences" since 2005
Paul,
I didn't mean to be pedantic. Tung oil may benefit from the addition of metallic driers in any given proprietary formulation. But metallic driers are very marginally useful commercially for tung. Heat activating the polymerization process is much more importatant in tung oil.
Linseed can also be heat activated. But metallic driers are so effective with that oil (compared to the slight effect with tung) that no commercial linseed oil preparation meant for finishing is without driers. The term "boiled" linseed is completely misleading as heat activation is simply not used in commercial preparations.
Rich
From my quick digging, I see that some commercial blends use driers with Tung oil, while others don't. It looks like Japan driers will be used in tung oil based wiping varnishes, but not used in an oil finish.
There are some interesting chemistry differences between tung and linseed oil polymerization processes. But I suspect few readers would either enjoy reading about them, much less understand them. But I think the following guidelines are reasonble:
For oil/varnish mixtures using tung oil, adding Japan driers is reasonable, although for various reasons the driers have less effect on Tung oil than linseed oil.
For a "pure" oil finish, using polymerized (heated) tung oil is fine without the use of driers. This may lead to a more cross linked film with better gloss than if driers had been added. The critical step, as you point out, is the heating which promotes cross linking during polymerization.
Now that I've got my curiosity up, I think I might do some experiments this summer in my lab -- I mean shop!
Paul
PS a Google search on tung oil polymerization driers yields a couple of easy to follow articles, if anyone out there really is interested...Recommending the use of "Hide Signatures" option under "My Preferences" since 2005
Rick,
Is "heat activated" in a temperature range that is practical for a small shop to achieve?
Thanks - Doug
Doug,I seem to remember reading that a temperature range of 140-160 F. is used.Rich
Thanks - I think I'll pass on applying oil in that temp range although it would be an interesting experiment.
As others have indicated, pure tung oil is a poor choice for your application.
It is the slowest drying of the so called "drying oils". It can take weeks for it to fully polymerize. It's even slower than raw linseed oil.
Second, it will impart an amber hue to a light colored wood. While somewhat less than linseed oil, tung oil is still amber in color. It will also continue to become more amber over time.
Finally, it is a very poor treatment for a surface that will get any use. Water and water vapor will pass right through it and it offers little abrasion protection.
Say whaaaa...
Couldn't believe i read that.
Tung oil is a great moisture barrier. One of it's first uses in China was water-proofing junks.
I've used it on many tables because it's beautiful but mostly because i don't have to worry about water rings.
It doesn't yellow nearly as bad as many others.
dshea,
As others have said, oil, any oil is a bad choice for your needs, including preventing maple from yellowing. I agree, you do not want that to happen - really ugly.
Consider ultrablond shellac. Shellac is as beautiful a finish as can be applied to wood. It can be rubbed to resemble an oil finish, and while not alcohol-proof, it is water resistant and much more durable than generally believed.
You can use lacquer. "Ordinary" nitrocellulose lacquer will yellow the maple. You need to use acrylic CAB (cellulose acetate butyrate). I like the Sherwyn-Williams product with its matching sanding sealer. It goes on water white and will not yellow the maple nor allow the maple itself to yellow. Depending on your ability, it can be applied as a thick film finish or rubbed to look like an oil finish. It's gorgeous.
Lastly, don't discount the newer water based polyurethanes. Vararthane Diamond varnish is quite amazing. It is very forgiving. It takes an act of faith to believe it will work because it doesn't look good when first applied. The first coat is a sealer coat. It will raise the grain which you need to gently sand back (no problem).
The second coat, too, may raise a little grain. Sand it back, also, but dont try to completely level it. Then apply at least 3 more coats, at least 48 hours apart. Completely level each of these coats, just before the new coat. Use a grit one higher than the last one used on the wood and make sure you get a completely even, dull scratch pattern. The sanding dust should be a dry, fine powder with absolutely no clogging of the paper. If not, the finish is still too soft, wait another day, then try again.
Before each level sanding the finish will be amazingly clear (especially compared to the way it looks just after application). Eventually it will get as hard as any finish you can use. Let the last coat harden 2 weeks. Then level it as before. Then rub with 4-0 steel wool. It may look as you want at that point. If not continue to rub with 600 grit wet-or-dry, lubricated with either mineral spirits or water containing a few drops of liquid diswashing detergent. Go on to higher grits of wet-or-dry as you like.
You will be pleasantly surprised at the soft sheen and quality of the finish. This ain't your father's water based finish!
Rich
First I would like to thank everyone for their help. Although I have read a lot on finishing, I have little experience and am finding it very frustrating. All comments are appreciated.<!----><!---->
The aesthetic I want is a "close to the wood" look, so I chose oil rather than a varnish. The idea of sealing wood just seems disturbing to me. Maybe I'm saying this because I just read George Nakashima's book. Anyhow, I have a few more questions if you guys have the patience.<!---->
1. Does tung oil go bad like a varnish?
2. If oil penetrates wood and does not sit on top, why would oil/varhish blends make sense to layer? It seems to me after the first or 2nd the wood would be sealed by the varnish in the blend and render the oil in the 3rd coat useless. Doesn't it just sit in the varnish matrix in these added coats doing little to help the finish?<!---->
3. Do all polyurethanes yellow over time? What about Shellac?<!---->
Thanks again.
I'm kind of put off by your disparaging of the cheap minwax poly that is hip these days. I began using minwax poly about ten years ago because it was an effective wipeon that gave a good looking (with a little rubbing)and durable finish and I could find it locally. I really liked it and felt somewhat ashamed because it was mass market stuff and not "pure".
Personally, I feel vindicated and I feel like my judgement isn't so far off after all with FWW giving the best overall and best value in their testing. I bet those FWW folks entered the test expecting one of the high priced afficionado brands to bury the mass market stuff!
I've used tung oil also. My 20 year old koa drafting table with the english walnut veneer surface is finished with "tung oil". But, while time has erased my memory of which tung oil it was, I suspect that it was not a pure tung oil and was actually formulated with other resins and heavy metal driers.
The finish is nice. It's a classic subdued oil finish that has worked well with the koa for a drafting table. It would be a disaster for a dining table or a coffee table because it doesn't provide any kind of a moisture barrier or effective wear protection.
The minwax poly has held up perfectly for my straight grained DF kitchen cabinets for 5 years despite cleanser, spills, and agressive cleaning by a cleaning service in a hurry. The butcher block counter over the dishwasher and the recyclables cabinet is preforming much better with 7 coats of wipe on poly than the catalyzed lacquer that the factory used.
Wipe on poly isn't the best finish for everything, but there are applications where it performs head over heels above those purist finishes and looks much better after a few spills. Around here, that's a month or so!
Edited 7/14/2005 2:09 am ET by telemiketoo
I can see where you're coming from. Maybe hip was the wrong word to use. I did not intend it to have such a negative connotation and certainly not to disparage anyone's work. Cheap meaning inexpressive not inadequate. Anyhow, it seems like the tung oil is aesthetically more appropriate for darker woods and not for woods like maple. Would you agree? I apologize for the beginner level questions, my intentions are sincere. Do you have answers to my previous three questions? Thanks for the input.
"Anyhow, it seems like the tung oil is aesthetically more appropriate for darker woods and not for woods like maple."
I think you might want to consider that there are applications where you want to use the properties of oil or oil blends to create a desired balance between contrasting woods. I'm building some cherry furniture with quilted big leaf maple panel door inserts and I am using the darker properties of a mix of linseed and tung oil to pop the grain and adding a color tone that is complementary to the cherry. I am not striving for maximum contrast between the cherry and the maple.
The more you work with different woods and combinations of woods you will find that you need to stay open to experimenting with what works best for a particular piece rather than a set of rules that can limit your creativity and diminish the potential of your craftsmanship.
One of the few areas that virtually all on Knots will agree is that you should always test your finish scheme on scrap and have patience.
With respect to your original questions, tung oil is a penetrating oil. You can reduce the effect of the current coats by some reasonably aggressive sanding once the tung has completely dried but but there will be some residual "yellowing". The sanding could create some areas of splotchiness.
Edited 7/14/2005 11:09 am ET by Doug
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