Pure Tung Oil or Polymerized Tung Oil?

[Randy Goodhew]

BRAVO!

The misinformation about Tung Oil, and other non-mainstream finishing products, that "echoes" on this and other forums is astounding.

The traditional huanghuali wood furniture were pretty much all finished with pure tung oil and have lasted for centuries - It is a wood/oil combination that is absolutely one of the most beautiful woods (off course taste is individual) and the real antiques (and raw wood for that matter is very highly prized. It is said to take more than 100 years for the wood to reach its ultimate beauty. I had to take a huanghuali desk and chair and chair apar as they were in a container (with a lot of our other antiques) that was dropped over the side in a harbor during a transatlantic move - all the hide glue dissolved and the finish obviously too a beating. However - since it is a $50K+ piece it was worth my while (after the insurance company had paid for all the "destroyed" furniture) to take it fully apart, clean up the pieces, thoroughly dry all the pieces in a controlled fashion, assemble them and then re-finish from scratch with the only finish that does the piece/wood justice - straight tung oil. Sure it is a tedious process and is best done in multiple thin coats without sanding in between and the timing such that the next coat is applied between "rubbery" and "fully cured" stages. 14 coats is what I did (over a couple of weeks) and then rubbed out in multiple stesp to a pretty nice semi-gloss sheenwith an incredibley deep and rich lustre. The piece has been evaluated by a couple of high-end antique evaluators and they put it as "fully and originally restored" at a $75k+/- price range.

The finish is very hard (obviously after the appropriate cure time) and water, alchohol resistant and shows off the wood beautifully.

Granted, this is not a restoration project for the faint of heart and the finishing process is very involved - BUT - it can produce some absolutely beautiful and pretty durable results. It is one of the finishes that draws max beauty out of many different wood species. it obviously helped me a great deal to have learned about fine antique furniturerestoration from my dad, who was one of the premier furniture restorer in Europe (talking about real antiques 200+ years old).

So - not an easy finish (in raw form) but worth it for the occasional exceptional piece. Some of the tung oil blends provide very nice results in a much more user friendly format.

[Steve Schoene]

Pure tung oil just can't achieve a hard, glossy film. It is much too soft when cured, and for that matter, it shrinks as part of the curing process leaving a satin finish the most that can be achieved since it is too soft a film to rub out evenly. Some seem to want to attribute a special aura to tung oil, for reasons not entirely clear. Tung oil,by itself, makes a lousy finish, even though it is an excellent ingredient to use in formulating varnishes.

[Randy Goodhew]

Bravo!

There is a tendency in these kinds of forums to treat some finishing products with rationalized ignorance and extreme language. Tung Oil is one of those products. Neither demonizing nor deifying the use of Tung Oil solves any questions or problems about the best uses of this product.

Cult-like adherence to misinformation about Tung Oil continues to echo whenever this product is discussed. Facts shouldn't be confused with personal preferences, and misinformation shouldn't be used to support a position of ignorance about a product.

Everyone is entitled to their personal opinions about finishing products and techniques. However, blatant misinformation casts a shadow on the veracity of this forum and especially the self-appointed gurus who continue to echo common non-facts.

More later...

Pure tung oil just can't achieve a hard, glossy film. It is much too soft when cured, and for that matter, it shrinks as part of the curing process leaving a satin finish the most that can be achieved since it is too soft a film to rub out evenly. Some seem to want to attribute a special aura to tung oil, for reasons not entirely clear. Tung oil,by itself, makes a lousy finish, even though it is an excellent ingredient to use in formulating varnishes.

[Scott Holmes]

Randy,

Since you deal only with facts; which is a very good trait....

Take a few drops of pure tung oil and few drops of boiled linseed oil and spread them out (separately) on a piece of glass or plexiglass. Give each sample time to cure; give the BLO 24-48 hours the pure tung oil a week.

Now with these dried and cured oils test how "hard" they are on the surface of the glass. If you also test a few drop of varnish while you do the tests for the oils you will find that the varnish is hard and clear the oils will be rubbery and wrinkled.

[Prashun Patel]

I'm not in the same league as Scott and Steve, but I will say that I think the main difference is in the possible methods of application. This is all my own experience only - and not an expression of universal truth:

A pure tung oil finish has to be applied in extremely thin coats - so thin that almost everything absorbs into the wood or is buffed off. A pure varnish finish can be applied this way, or can be left on the surface in a thick, thin, or non-existent coat. The grey area is in between with an oil/varnish blend. Some small amount of oil will not prevent building, but in general these function best when applied like a pure oil finish.

Any hardness that I feel from a wiped on/wiped off finish (oil, varnish, or oil-varnish) results from a combination of the sealing of the wood and the burnishing of the wood when sanding with higher grits of sandpaper.

On extremely-thin-in-the-wood finishes, I cannot see any visual difference between a tung oil and a varnish finish. But I don't think it's possible to get a BUILT UP tung oil finish that is hard. I believe that because the times I leave even a slick oil coat on a surface that's absorbed enough, it stays gummy for a good long while. If you gave an oil finish 100 years to dry, then perhaps it'd become a varnish good and proper...? But I've made the mistake of applying more coats over a 'soft' coat, and I can say it does not allow the whole shebang to dry properly - even for months.

So, my advice to any newbies following this thread is to minimize the risk by not attempting to build up an oil finish. How much protection you need is a matter of personal preference.

[Howard Acheson]

If you doubt the veracity of Scott's statement, you can try a little experiment. Get a clean piece of glass and put it on a flat surface. Now pour a puddle on tung oil onto the glass and set it aside on a flat surface. Go back every week or so a see if it has "dried". Test it's hardness by impressing your fingernail into the puddle.

I think you will find that the tung oil does not get hard as a standard oil based paint gets hard.

[Randy Goodhew]

Randy,

Since you deal only with facts; which is a very good trait....

Take a few drops of pure tung oil and few drops of boiled linseed oil and spread them out (separately) on a piece of glass or plexiglass. Give each sample time to cure; give the BLO 24-48 hours the pure tung oil a week.

Now with these dried and cured oils test how "hard" they are on the surface of the glass. If you also test a few drop of varnish while you do the tests for the oils you will find that the varnish is hard and clear the oils will be rubbery and wrinkled.

This is a common Internet "echo" and is not categorically true.

Also, the term "varnish" is too vague.

Blessings.

[Scott Holmes]

Here's a few pictures of the sample piece of glass that I pass around my finishing classes. Note the varnish is hard and shiney the oil/varnish blend (Watco Golden Oak) is not hard or shiney.
This is not an internet "echo" these are pictures I just took to show you the results.
Varnish & Danish oil on glass.jpgDanish oil on glass.jpgvarnish on glass.jpg

[Devin Ginther]

I know this thread is quite old but I would like to correct misinformation and misdirection from Scott & others.

Scott is simply 100% wrong on this topic. It is completely false to say that Tung Oil is a poor finish choice for wood. I'd imagine polyurethane is the recommended solution given his responses. And I say this respectfully as Scott's experience and general finishing knowledge is typically EXCELLENT. He just happens to fall short on this particular subject. I'm sure I could learn quite a bit from him overall as I've read many of his very insightful and intelligent posts over the last few years. But I have to agree completely with Randy on this one.

We build natural live edge furniture and often produce dining tables that sell for $20,000+ to many of our clients on the East and West coast. We very often use tung oil on these heirloom pieces of furniture. And all our in-house varnishes are based on a percentage of tung oil. The idea of putting pure tung oil on a glass plate and letting it oxidize / cure shows a lack of knowledge. Pure tung oil has NEVER been intended to be used like this.

FYI, Watco is a oil/varnish blend BTW and likely is a blend of tung oil, BLO and petroleum based solvents. Many mfg are misleading consumers with a branded name containing "tung oil". Formby's is the best example of this of all. Total scam.

I can clearly show hardened pure tung oil. But you must setup the experiment for its intended use. Pure Tung Oil cures extremely slowly sitting as a puddle on a surface. No one would ever recommend using this product like this. You'd have a very tacky surface weeks later. However, try mixing in some sawdust (representing tung oil soaked in wood) and see what happens over 24-48 hours.

Having said all this, tung oil certainly has its advantages and disadvantages. If you are seeking a durable, above the surface (or film finish) then I certainly do not recommend pure tung oil. However, if you are seeking what is probably the best looking finish, that offers good moisture repellency, resilient against most household cleansers & acids, has no VOCs, is food contact safe, and is very easy to re-freshen THEN tung oil is a EXCELLENT choice. And there are tricks we use (sorry, trade secrets to our finishing techniques) to accelerate the curing process of tung oil. And I am not talking about any metallic driers or additives. Problem is, a LOT of people don't have the experience level to know how to maximize the potential of tung oil. It MUST BE APPLIED correctly to maximize all its advantages of a finish. It generally takes us 14-21 days to correctly apply a fantastic tung oil finish. This is certainly a major downside to tung oil but the results are speculator!

Making a generic statement that Tung Oil is a "poor finish" shows a general lack of experience & knowledge. And as Randy states, the misinformation continues!

And PLEASE don't tell me that BLO is just as good but a lot cheaper. BLO is inferior & generally is a poor finish choice compared to many other alternatives. Then again, BLO has its place as a low cost additive to varnishes. I'd never personally use it. But I understand it is cheap and it dries quicker as metallic driers are added which only compromise the clarity of a BLO based varnish finish.

I generally spend $500-1000 each year testing and evaluating finishes in controlled experiments. I'm still waiting for waterborne finish technology to obsolete everything. Still another 10 years away I figure.

If anyone really wants to understand the science behind curing please start here:

Organic Coatings: Science and Technology

By Zeno W. Wicks, Jr., Frank N. Jones, S. Peter Pappas, Douglas A. Wicks

Here's a few pictures of the sample piece of glass that I pass around my finishing classes. Note the varnish is hard and shiney the oil/varnish blend (Watco Golden Oak) is not hard or shiney.
This is not an internet "echo" these are pictures I just took to show you the results.
Varnish & Danish oil on glass.jpgDanish oil on glass.jpgvarnish on glass.jpg

[Scott Hearn]

All I know is that the pure tung oil that I put on my cutting boards beads water (and blood) like water off of a duck's back. It takes a good long while with wet sanding the piece with the oil and long dry time, but the results are worth it. It will darken over time but I kinda like the old school finish look and feel anyway, plus maintenance is simple. My experience concurs with Devin Gunther's perfectly. I buy mine from Real Milk Paint Co.

All that said it's not the best choice for every application, you have to match a finish with intended use. For fine crafted pieces with fantastic grain there's not much better of a choice than oil. Tung is my preference because it gives superior protection but linseed looks great too, just take a look at Holland & Holland gunstocks.

[Howard Acheson]

>>>> One local woodworking shop recommended General Finishes Arm R Seal but I am concerned that might yellow. Another recommended pure Tung oil thinned with mineral spirits.

Arm R Seal is an oil based poly varnish. It will determinately "yellow" over time. Pure tung oil is slightly "yellow" upon application and will slowly become more yellow over time. Tung oil is also not very protective or durable. Your best bet is to use a waterborne acrylic poly. It goes on water clear and does not yellow. However some manufacturers are formulation their waterborne with an amber tint to closely mimic oil based poly.

As always, test your finishing plans on scrap. No tears.

[Bob Wingard]

The traditional huanghuali wood furniture were pretty much all finished with pure tung oil and have lasted for centuries - It is a wood/oil combination that is absolutely one of the most beautiful woods (off course taste is individual) and the real antiques (and raw wood for that matter is very highly prized. It is said to take more than 100 years for the wood to reach its ultimate beauty. I had to take a huanghuali desk and chair and chair apar as they were in a container (with a lot of our other antiques) that was dropped over the side in a harbor during a transatlantic move - all the hide glue dissolved and the finish obviously too a beating. However - since it is a $50K+ piece it was worth my while (after the insurance company had paid for all the "destroyed" furniture) to take it fully apart, clean up the pieces, thoroughly dry all the pieces in a controlled fashion, assemble them and then re-finish from scratch with the only finish that does the piece/wood justice - straight tung oil. Sure it is a tedious process and is best done in multiple thin coats without sanding in between and the timing such that the next coat is applied between "rubbery" and "fully cured" stages. 14 coats is what I did (over a couple of weeks) and then rubbed out in multiple stesp to a pretty nice semi-gloss sheenwith an incredibley deep and rich lustre. The piece has been evaluated by a couple of high-end antique evaluators and they put it as "fully and originally restored" at a $75k+/- price range.

The finish is very hard (obviously after the appropriate cure time) and water, alchohol resistant and shows off the wood beautifully.

Granted, this is not a restoration project for the faint of heart and the finishing process is very involved - BUT - it can produce some absolutely beautiful and pretty durable results. It is one of the finishes that draws max beauty out of many different wood species. it obviously helped me a great deal to have learned about fine antique furniturerestoration from my dad, who was one of the premier furniture restorer in Europe (talking about real antiques 200+ years old).

So - not an easy finish (in raw form) but worth it for the occasional exceptional piece. Some of the tung oil blends provide very nice results in a much more user friendly format.

I've read a bit about huanghuali wood, and how it was "traditionally" finished, and the only references I could come up with was lacquer ... "clear" lacquer ... and wax ... never saw a single reference to tung oil ... "pure" or otherwise. That was a really nice story, but lacking any facts or reference to brands of materials you are supposed to have used ... I for one am not buying it. Neither tung oil or blo have any place in my shop except maybe on shovel handles or such. Neither have any potential to be an actual finish, although they may have some use to some folks as coloring agents. If you have a finish that is hard, and water/alcohol resistant ... it is NOT tung oil ... they are mutually exclusive terms.

[Charles Taylor]

I've read a bit about huanghuali wood, and how it was "traditionally" finished, and the only references I could come up with was lacquer ... "clear" lacquer ... and wax ... never saw a single reference to tung oil ... "pure" or otherwise.

I'm no expert on the traditional finishing of huanghuali (a species of rosewood, for those who don't know), but note that lacquer was introduced as a wood finish only about a century ago.

EDIT: I was wrong. Read on.

[roger wiegand]

I had a container of Behlen pure tung oil leak in the back of my finish cabinet over a period of years. The hardened material can't possibly be dented with a fingernail, though it can be cut with a sharp chisel--it's not so hard that it shatters, though (unlike shellac). In removing the container the wood underneath gave way before the finish would separate from the wood. I don't use it for tabletops, as it will certainly mark with standing water, but not with spills that are mopped up within 15-20 minutes. So decent water resistance but by no means waterproof, by my estimation. No experience with alcohol spills. I expect it will probably dissolve, at least slowly, in methanol (and certainly in methylene chloride), less so with ethanol or isopropanol. I wouldn't use it to finish a lab bench.

[Michael Kaplan]

I've had good experience brushing water-based finishes with a foam brush. General finishes, Miniwax, et.al. Don't brush back and forth as they dry quickly, sand lightly between coats, and they dry clear and hard, took less than 100 years