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"pure" tung oil

labolle's picture

"pure" tung oil (post #110551)

Hi all,


I found out recently that I can get pure heat-treated tung oil here for about $20,00 U.S. per gallon.  When I opened the can it smelled nutty, somewhat rancid, and had the consistancy of of a very thick maple syrup.


To use it I thinned it 1-1 with paint thinner, wiped it on till the surface was as soaked as I could get it,  then wiped it off getting it  as dry as I could.  Waited 24 hrs and repeated.  Lovely stuff.  Really "pops" the grain on the ceder.  A nice amber tint to it too.  In fact I like it so much, that I sanded off the lacquer finish I had done on a few recent pieces to re-do them with the tung. 


So far, I have figured out that wiping off the excess as soon as I feel the coat is wet and even enough leaves less "gummy-ness" than coming back to wipe after half an hour as some places suggest.  Also, figured out that exposing it to sunlight as it cures speeds the process up.


Now for my questions:


1. How do I get the most "depth" and beauty out of this finish?


2. I am considering wet sanding with 600 grit once it seems fully hard, then re-applying another coat.  Good idea, or not?


3. Once it is finished I'm considering polishing it with a buffing compound a piano tuner gave me.  Then applying a coat of piano wax.  Good idea or not? 


4. For durability, would a top coat of sprayed on varnish be a good idea or not?


Yes. I realize that semanticly once I added the paint thinner to thin it it was no longer "pure" tung oil, but the thinner evaporates, and makes it much easier to apply.


Any suggestions for getting the most out of an oil finish would be appreciated.


 


Thanks.


 

SteveSchoene's picture

(post #110551, reply #1 of 12)

Working backwards:


4.  Adding varnish on top of the oil finish pretty much eliminates the effect of oil, except for a thin first coat which may "pop" figure slightly better than an oil based varnish alone would do.  The effect of the oil under varnish would be subtle. 


3.  Rubbing out with a abrasive compound doesn't make much sense on an oil finish which is very soft.  You can apply wax, if you like the added sheen most waxes bring.  With tung oil wait a month before adding the wax since it takes a long time to complete the cure.


2,  Wet sanding is good after the first coat, but not as a separate step but part of the application process.  It does smooth the surface a bit and arguably partially fills pores.  (If you wipe off early enough to avoid getting gummy, you wipe most of the "slurry" from the pores.) 


1.  Tung oil requires about 5 coats (more if heavily thinned) to achieve an even satin sheen on most woods.  You may find that less thinner works almost as easily.  Try 20% and see if you need to add more.  But don't try to build a film on the surface--it will be soft and unprotective.   


 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

Rich14's picture

(post #110551, reply #2 of 12)

What Steve said.


And . . .


Re: your having removed a lacquer finish in favor of the tung oil application . . . what a shame!


If you're willing, you can learn to apply and rub out a lacquer film to a much nicer appearance than the (still wet) oil application seems to be giving you now, and which will dull and wear away over time. 


Additionally, the lacquer is a real finish that will afford protection and durability immeasurably better than that which tung oil can produce.


Vegatable oils are an indispensible component of varnish preparations. Unfortunately, because it is so easy to produce an oiled surface on wood, they have been used alone for centuries as a "finish," and there is a whole culture and mystique surrounding their use. But used on their own, they are to wood finishes as masking tape is to wood gluing techiques.


Rich

labolle's picture

(post #110551, reply #3 of 12)

Steve and Rich,


Thank you for the quick replies.  I appreciate both of your replies, and am somewhat befuddled as to which is supposed to be a superior finish: oil or varnish.


As I understand it so far oil wins in overall looks and its ability to be fixed or touched up years later, and varnish is more durable. 


So far I have been spraying with a satin sheen varnish and find that it tends to dull the look of the grain with each additional coat.


So that leads to another few questions:


How do I get the most out of a varnish finish.


AND how do you know when a finish is finshed?   When an additional coat is not going to add to the look, but detract from it?   With both oil and varnish, when do you know when to stop? 


Also, Waxes.   When, and how much?


Thanks.

SgianDubh's picture

(post #110551, reply #4 of 12)

"I have been spraying with a satin sheen varnish...................... dull the look of the grain with each additional coat."


That's probably the root of your problem labolle. Sheens other than gloss contain flatting agents to break up the light so as to achieve the desired sheen. It's usually silica. Try opening three cans of your preferred varnish brand, one gloss, one satin and one matte. Notice that you can (probably) clearly see the bottom of the can with your gloss. Then observe that the fluid is milky and completely obscures sight of the inside of the can with the matte stuff. It will be that or the silica is sitting as a lumpy mass at the bottom the can and needs to be stirred up evenly throughout the varnish. Satin will be somewhere in between.


Several coats of satin or matte will give a cloudy appearance that occludes sight of the wood below. This is why, if you're going to apply two or three coats of a film finish most workers apply gloss for the first two coats and the desired sheen only for the last coat. If your plan is to apply ten coats of your varnish you can appreciate I'm sure that if they're all satin you'll end up very largely obscuring the wood from view.


Which is the best finish, oil or varnish? The answer, as is often the case, it depends. It depends on the end use of the piece of furniture. I'd never finish a coffee table with a pure oil finish. Too easily damaged with white rings, damage to the wood underneath, etc.. A film finish such as varnish would generally be a better choice. Pure tung oil could be a good choice for a lightly used piece such as a hall table that is essentially decorative rather than functional. Slainte.



Edited 6/21/2006 5:11 am by SgianDubh

SteveSchoene's picture

(post #110551, reply #5 of 12)

Richard Jones has hit this right on the head. 


Mostly you have reached the point where the decisions are esthetic--matters of personal preference which can only be answered by your own observation.  For example--how many varnish coats?  Most believe that a relatively thin film looks best.  This means varnish finishes usually take only 2 or 3 coats--depending a lot on the wood and how evenly the first coat penetrates.  By the time you get to three coats most of the protective effects will have been achieved, except for exterior applications where the thickness of the film adds UV protection.  In that case 6 or 7 coats of varnish are recommended.  That many coats gives a very "deep" looking finish that is occasionally desirable even if the extra protection isn't needed.  Its the kind of quesion only you can answer through experience and experimentation. 


Same thing with wax--do you like the look?  Wax tends to remove its own previous coats in the application process, so ideally you would never need more than one coat, although two coats does help deal with missed spots and the like.  Wax adds very little protection. 


With oil finishes the limit is largely based on the need not to let it build up into a film on the surface.  Oil finishes will need lots of maintenance so you are never really through. 


If you want to broaden and hone your esthetic judgement the answer is to look widely at the best examples you can find.  Go to museums.  Go to high-end galleries.  Even pick up books and look at the gallery pages in magazines or on-line. 


 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

Rich14's picture

(post #110551, reply #6 of 12)

labolle,


What the other 2 guys said.


I don't use finishes with flatting agents ("satin" finish varnish and the like). A satin finish is obtained by applying clear varnish, shellac, lacquer through to the final coat, and rubbing out the final hardened surface to the desired abrasive grade (4-0 steel wool through 1200 grit wet or dry used with a soap water lubricant gives various "grades" of satin sheen).


There is no question that a freshly-prepared wood surface onto which new oil has been applied and wiped as "dry" as possible is a lovely looking thing. I like the appearance of the wood surface itself seeming to glow, especially on tropical hardwoods. To my eye, however, the oiled surface loses it's attractiveness in hours, if not days, and certainly over the course of months. It becomes too dull. And it has no protective qualities at all. (I am not referring to a varnish/oil mixture which does have some minimal protective property due to the very thin film of hardened varnish. Almost all commercial, so-called "tung oil finishes" are varnish/oil preparations in which the oil actually is linseed, not tung. But you started this discussion referring to pure tung oil).


I do use oil/varnish preparations for pieces that are unlikely to receive any handling at all (such as picture frames) but plain oil is not in my repetoire.


The temporary quality of the oiled surface is apparent in the hoary old finishing "schedule" for oil which goes something like, "Once a day for a week, once a week for a month, once a month for a year, once a year forever." I don't think there is any real justification for such a schedule and I'm not promoting it at all, it's one of those things that once started, gets repeated as gospel by people who get caught up in such things. I offer it simply as indication that those who involve themselves in finishing wood with oil recognize the need to renew the finish, often.


To me, the word "finish," means "done." Unless damaged, a varnish, shellac or lacquer finish never needs additional work. Using clear finishing materials, it is possible to achieve any final appearance desired, including the look of a freshly oiled wood surface. And once done, it stays that way, almost forever. It just takes time to learn how to do it.


Rich

labolle's picture

(post #110551, reply #7 of 12)

"Using clear finishing materials, it is possible to achieve any final appearance desired, including the look of a freshly oiled wood surface. And once done, it stays that way, almost forever. It just takes time to learn how to do it."

Rich, Steve, Richard,


Thank you all. I have read and re-read each of your posts.  A lot of information there.  I have to admit that I love the look of a freshly oiled finish.  However, I am starting to realize that it may be just about impossible to maintain that look with oil alone. 


So then, how do I use lacquer and achieve that kind of warm, grain-magnifying, color-shifting-as-you-walk-around-the-room-and-the-sunlight-hits-it-from-different-angles, kind of sheen? (in my earlier posts I mentioned spraying "varnish", but meant to say "lacquer", which, besides oil, is the only thing I have tried so far).

Rich14's picture

(post #110551, reply #8 of 12)

"So then, how do I use lacquer and achieve that kind of warm, grain-magnifying, color-shifting-as-you-walk-around-the-room -and-the-sunlight-hits-it-from-different-angles, kind of sheen?"

With the caveat that a "freshly oiled wood surface" means one that has been oiled, wiped as dry as possible and let to "set up" for a day or so, not still wet with applied material, either shellac or lacquer applied in many thin coats can be rubbed out to the same appearance. Even varnish can do it, but varnish is almost always used as a thick-film finish.

Shellac and lacquer can be padded on in several ways. Many finishers regard french polishing with shellac as the ultimate expression of the craft. Depending on how much of a purist one wants to be, french polishing, or more accurately, shellac padding can be done without the pumice required in the classic method. Without the pumice, wood pores are not filled by the process and the finished surface tends to look just like an oiled surface (which of course has no filler prior to oiling.

In fact, if you get any good with padding shellac or lacquer (and it DOES take time to learn - there is no hurrying the process), you will wonder why you thought an oiled surface was good looking. Depending on your skill, you can leave the wood looking like there is no finish there at all, just a polished surface, or you can build the film to whatever thickness appeals to you. Of course, very thin films are less durable than thicker ones, but even very thin films are amazingly durable (just don't expect to finish a dining table this way).

But you don't have to use french polishing techniques or padding, you can spray shellac or lacquer using the lowest cost (aka cheap) equipment, let it harden for a few days and rub it out beautifully. You start with about 320 grit, work up through 4-0 steel wool, 600, 800, 1000, 1200, auto rubbing compound, auto polishing compound (forget pumice and rottenstone - too inconsistent), then swirl remover, or stop anywhere in that spectrum, depending on what you like.

While you're learning, trying to get a continuous, but very thin finish film, you'll get frustrated by rubbing right through to the wood, needing to start over. But eventually it starts to work, and somehow you get the feel and leave just enough finish without burning through.

If this sounds hard, it is! An oiled finish is absurdly easy to do. But you get what you pay for. You don't learn finishing in a day or a week or a month, or by reading these messages or books. But this is where you start. And you have to do it a lot, and take notes about the results, and use a few differnt woods to notice how the finish responds differently. In 6 months to a year, if you're diligent, you'll start to really like what you can produce. Welcome to finishing!

PADDYDAHAT's picture

(post #110551, reply #9 of 12)

Rich, I am bummed out, I am an old oil  guy, only because of the apparent complexity of finishing. I understand your post and it's demonic final coment! But how do we scope out the path to take to fine finishing? The number of guns/ types /solutions/tecniques(rubbbing with what-how long etc.) Where do we find the answers to produce a fine finish on a well crafted piece? I accept the trial and /progress effort on scrap in detail but the base tests need more direction -where do we go? Is there a littany of books that describes at least the basics? Thanks ,Pat

WillGeorge's picture

(post #110551, reply #11 of 12)

YEP I agree..

NOW 'IF I COULD' apply it like the China folks did 4000 years ago I be happy!

Have a great day.. Life is wonderful even if you are having a bad day!

BossCrunk's picture

(post #110551, reply #10 of 12)

Film forming finishes don't allow anything to touch the wood - moisture, spills, etc.  The sheen can be customized.


However, film finishes are not easy to repair and a heavily used piece will develop scratches in the finish itself.  Think conference room table.  The result can be piece that actually looks worse down the road, due to the myriad small scratches, than one with a simple oil and wax finish. 


Most defects you see in a piece with a film finish are in the finish itself and actually harder to repair then the occassional ding or mark that might occur to an oil finished piece.  A little sanding and a reapplication of oil and wax can restore an oil finish to a like-new status.  You'll have to completely strip a film finish to effect most repairs or use a finish amalgamator which won't always work.


You should have all sorts of finishing routines in your repertoire.


Here's an article you'll enjoy:


http://www.taunton.com/finewoodworking/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=2266

Some on this forum dismiss oil finishes out-of-hand.  Ignore them.  Please.


Edited 6/22/2006 3:17 pm ET by BossCrunk

labolle's picture

(post #110551, reply #12 of 12)

Thank you all for your input.   I surely won't be dismissing oil finishes out-of-hand.  So far I have had some good results with multiple coats of tung oil followed by a buffing paste used to generously rub it out followed by an automotive paste wax.  I will be taking some scraps and testing all of the techniques and variations I can to find out how they each differ from the other.


Best wishes from Taiwan.