I made my first project and finished it with tung oil as follows:
3/4" walnut
3/4" mahogany Finish sand to 220, clean with chip brush and tack rag First coat 50/50 tung oil to mineral spirits- wipe dry let cure 48 hours
2nd coat 50/50...wipe dry...72 hour cure
3rd coat 100% pure tung oil. Wipe dry, wipe next day, wipe next day
6 day cure in garage 85 daytime temp..70 night temp
Now after 7 days, it appears dry, matte finish, but...when i put my hand on it for 4-5 seconds, oil appears where it was touched and oil is also on my hand. All the stuff I read said a week curing would be sufficient. Also, it smells like a month old bag of Lay's tater chips.
Is the slow dry normal? Can I speed up the drying? How long before it cures? When will the smell go away?
First mistake was putting on too much oil. Tung oil is a penetrating finish; it doesn't build a film. There is no point to more than one application because the subsequent applications have no place to go if the first one was adequate.
I would try cleaning an inconspicuous place with mineral spirits; though I frankly have no idea what will happen.
I've experienced slow curing time for pure tung oil in the past. My experience is that it cures faster if the surface is exposed to moderate amounts of sunlight.
I've heard of that, but I've never heard of french polishing with tung oil.
Sounds like the OP had been over-generous with the oil application. Personally I use a commercial oil blend (tung + thinners + driers) for the first couple of coats and don't switch to pure tung until I'm building the finish - maybe another 4-6 coats. Sometimes I even thin the first coat even further.
I'd try scrubbing this piece down with thinners ("mineral spirits", pond-side) and reducing as much oil off the surface as possible. Then give it a week, and re-coat, but _thinly_ this time.
If you're _really_ screwed, switch to a shellac-over-oil finish. But this doesn't work if the undercoat is "oozingly" thick.
So what is it he's feeling on the surface, if not a tung oil film?
Advice, as in other recent threads, is to use a "tung oil finish" with driers and/or varnish added to firm it faster, after wiping off the surface film to get the dust it's collected out of the way. Either that or warm the whole thing up to speed the cure. Wipe off what bleeds off when warming.
I see a lot of messages on this board about using pure tung oil and for the life of me I don't know why people are bothering with it. Pure Tung oil never seems to dry. I would use the Minwax Tung Oil finish. In fact we have been using the finish for all of our furniture for over 18 years with great success. I realize that it is Tung Oil/Varnish mixture with a dryer, but the fact is that it makes an excellent finish when applied correctly. It is easy to apply, easy to maintain, and does not possess any of the bad characteristics of most other finishes. You never have to worry about your finish cracking, chipping, fading, discoloring, orange-peeling, or any of the other nasty things that can happen to furniture. It is more water resistant than other oil finishes, and builds a silky smooth satin finish over the wood with a minimum amount of effort. Tung Oil never needs to be stripped and refinished. If a finish ever becomes dull, you simply apply more finish.
And this is how we finish our cherry furniture.
The key to a great finish starts with sanding. Table tops are sanded using a belt sander equipped with a sanding frame with 120 grit. We then switch to a random orbital sander with 120 grit. Next we sand the top with 220 grit also on a random orbital. The third step is to buff the top. I take a piece of paper towel and put it between the table top and the 220 random orbital paper and let it rip. The paper towel will do a good job in buffing the top until it finally rips apart and blows all over your workshop.
Next take some Minwax tung oil finish a pour some in a plastic bowl. Wad up some paper towels (Bounty is good because it is soft) and apply a generous amount to the top. Then take some clean paper towels and wipe it completely off as if you did not mean to apply it to the surface in the first place. Just when you think you have removed all the excess tung oil, take a clean wad of paper towels and do it again, moving with the grain from one end of the top and moving off the other end, like an airplane landing and taking off again from the surface of the table top.
Allow the piece to dry for 24 hours. This WILL dry unlike the pure tung oil. Lightly sand the surface with a piece of 600 grit paper. And re-apply another thin coat of tung oil, allowing it to sit for a moment and then wiping it off again as described above.
If you live in a fairly dry region of the country you can get away with applying 2 coats a day. (Except after the first coat - let that dry 24 hours.) Here in New England where it is humid in the summer you can only get away with one coat per day.
After 5 applications, you should have a silky-smooth finish.ready for wax.
It makes a great finish, without all the headaches of other finishes.
"Build a film" is a term of art that implies that at some point in the foreseeable future it is going to be _dry_ film. If you ignore the drying part you can claim that axle grease is a film-building finish--you can put it on 6 inches thick but you're going to continue to have a board covered with a mess of axle grease and not anything that anybody would call a "finish" until Hell freezes over.
Sure sounds like you did all the right things and yes it takes an oil finish some time to cure completely.
You might be experiencing some bleeding of oil or possibly you have some high humidity problems but those are just guesses of course.
If you have to get it out of the shop you can try wiping the surface with mineral spirits then drying with a clean rag. something that may have to be repeated.
There isn't much more I can think of that you can do now other then doing a surface finish and sealing off the oil but then you'd spoil the look.
In the future you could try a Japan Dryer added to the oil to speed up the cure.
I _wouldn't_ try warmth or sunshine on it, in an attempt to "get it to cure".
Tung oil doesn't cure worth a damn. Boiled oils cure, but even they are slow about it. Raw tung oil though is just going to skin over while the layer underneath sits there and doesn't even think about curing, no matter what you do to it. Maybe gamma rays...
I think you've got to take some oil off that surface before you can achieve anything.
Precisely why I told him to wipe the sticky film from the surface in the previous sentence.
The process of oxidation and cross-linking is speeded up, as are most reactions, by elevated temperatures. Also, there is, by default lower humidity, which lets the lesser volatiles escape..
I've never had a problem with pure tung oil not curing. I have had a problem with boiled linseed oil not curing and remaining slick and waxy for months.
Others have reported they never have a problem with boiled linseed oil but do with pure tung oil. I cannot explain these apparent contradictions in experience.
For any oil finish that does not harden properly I suggest wiping the surface with turpentine or mineral spirtis to remove any residual oil on the surface and then flooding the surface with mineral spirits into which a small amout of Japan drier has been added. Then keep the piece in a warm place with low humidity.
Oil finishes cure by an oxidation/polymerization process, which proceeds faster at a higher temperature and is itself exothermic, hence the danger of spontaneous combustion with all drying oils and oil finishes. Some polymerization processes evolve water and can be inhibited by high humidity, I don't know if that applies to tung oil.
Next time you finish, don't use so much oil, 1 teaspoon / sq. ft is good enough to color the wood and bring out it's natural beauty. Oil is a non film building process, has little protection other than to seal the wood pores. If you want a quik finish that looks natural , and gives some protection. Small amount of oil, I use a resin base oil, Watco usually, wipe dry let dry usually 48 hours depending on drying conditions, then apply either a Watco wipe-on poly, or reduce Straight Poly by 20-30% and apply with a pad of cheese cloth folded into a ball, called a finishing Rubber. Pour reduced Poly into pie pan and let rubber soak up contents and apply in even strokes. . Also, like a few of the others said , take Mineral stirits and a scotch brite pad, white or lite green and wipe surface , keeping it wet for a few mins. then wipe with a clean dry cloth. You may have to do this process several times. The wood you used is very porus and will soak up alot of oil.
Oils dry because they are exposed to oxygen in the air. They harden, more or less. The thicker the standing film of goo the slower the oxygen diffuses through the goo into an area where it's needed to cause more drying. If the goo (film overlay) is thick enough, underlying oils will never fully cure.
A Tung oil "film" is not super-hard. There's a test for finish film hardness called the pencil test. You know how pencils come in #1, #2, etc? - those numbers are related to how hard the pencil lead is - the higher the number the harder the pencil lead. The test: you try to make a dent in a finish with increasingly harder pencil leads you record the hardness number that first makes a gouge or dent.
I'm not saying a really hard film is good or bad, just presenting an organized way to look at finish hardness.
Tung oil that has cured for 30 days has a pencil hardness of 1.0+, NC lacquer is about 3.5 or 4.0
In practical terms. a thick layer of tung oil, assuming you could fully cure one, would make a fairly soft finish. I'm sure it wouldn't be good as a writing surface, for example. However it would resist bangs and other kinds of abuse better than NC lacquer would - precisely because it has some give.
Coats were applied very sparingly, rubbed in with a terry cloth, then wiped "dry", after 20 minutes each time. I didn't let a film remain. There seemed to be "dry" spots after the first two coats- so it appeared there was not adequate coverage the first two times. The last coat did seem a little "filmish" though before wiping 20 minutes later.
Thanks for the info fellas. I will let it sit for another week, then I will try the spirits + Japan Drier. Thanks for the tip. BTW, there is no surface film, but my skin wicks the oil out of the wood.
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