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Tung Oil Smell

Discussion in 'Woodturning Discussion Forum' started by Ed_McDonnell, Aug 16, 2007.

  1. Ed_McDonnell

    Ed_McDonnell

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    Bought a bottle of "100% pure tung oil". I can't come up with a good description of this stuff other than to say it really smells bad. I've used other finishes with tung oil in them and they smell nothing like this. Could it have gone rancid? The oil drys as expected and once the tung oil is dry it doesn't have any smell. I suppose I could just not like the smell of Tung Oil..........

    For those who have used "100% pure tung oil", what's your opinion of how it smells? How do you know if your oil finish has gone rancid?

    Any thoughts?

    Ed
     
  2. Angelo

    Angelo President Emeritus

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    Tung Oil

    Tung oil has a very distinct odor.

    I love the smell! From time to time I will recoat the handles of my tools so I can have the smell on my hands. The odor brings me back to a time when I would make handles and sharpen all the tools for a now defunct turning supply company "Full Circle".

    However, don't let me be the judge, I think turpentine has a great smell too! Reminds me of art school.........

    Angelo
     
  3. ScottH

    ScottH

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    I agree with what Angelo said - a very distinct smell. That's the good thing about tung oil - you can always tell what it is!

    Scott
     
  4. DMcIvor

    DMcIvor

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    stinky tung oil

    Ed-

    That doesn't sound right. I use pure tung oil (which I mix with a drier), and straight or blended it has a slightly nutty and pleasant smell. My guess is you have a rancid batch.

    Don
     
  5. Ed_McDonnell

    Ed_McDonnell

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    I think I would describe the stench that filled my shop more as "da stink" than "distinct".

    After reading Angelo's response I started wondering if I maybe had a bad nose day the other day. I went out to the shop and took another sniff of the tung oil right in the bottle. It didnt' smell all that bad.

    I then took another piece of the wood that I used it on and when applied to that wood the worst odor imaginable filled the whole shop!!!! I'm not sure what the wood actually is since I salvaged it from a wood pile the other day. It looks like black acacia, but it smells more like some type of rosewood. The tung oil leaves a beautiful finish on it, but I think I'll be using it outdoors with any more of this wood.

    Ed
     
  6. Rob Wallace

    Rob Wallace

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    100% Pure?

    Ed:

    I have not ever used tung oil in the 100% form - I always dilute it with mineral spirits (at least to 70%, but more often at a 50%, 1:1, dilution) before applying it to wood. Maybe the mineral spirit smell masks any tung oil smell, but I've never found it to be offensive to me.

    There is a distinct possibility among various oil processors and finish manufacturers that there is variation in degree of purity of the oil as it is processed and cleaned after being pressed from the tung seeds. As in most natural products, the degree to which other impurities are removed from or are retained in the finished product may have something to do with how the oil smells; that is, how much other organic materials are carried through the cleaning process into the finished product.

    I am not sure tung oil will go 'rancid' without polymerizing. This is one of the "drying" oils, that, in the presence of oxygen, and heat/time will allow the oil molecules to link to one another to form the durable surface that we desire. Among the "vegetable oils", tung oil produces one of the hardest finishes (better than linseed [flax] oil) and although the drying rate is slow compared to other finishes, it still produces a good surface that protects the wood pretty well. The fact that the oil you are using seems to accomplish the polymerization process correctly, and does not smell badly after it 'cures' lends me to think that there are also volatile compounds in the oil which you find offensive that are released in the drying/curing process. I don't think your oil is rancid, at least in the sense of the partially-oxidized, non-drying oils (like corn oil or "vegetable oil") which can go rancid without altering its physical properties appreciably. I think truly 'rancid' tung oil would be a solid in the bottle!

    Tung oil comes from the seeds of a tree that is in the same family as poinsettia (Euphorbiaceae), and this family of flowering plants is known to have a complex chemistry in its tissues. The degree to which the processor has cleaned the native oil as it is prepared prior to packaging likely has a lot to do with how many other compounds are present in the final product. Because other commercially-available tung oil-based products are mixtures, they may not smell as bad (or at all) if: 1. higher purity oils are used, 2. the oil has been diluted by other additives in the finish, or 3. the volatile compounds causing the offending odor(s) is/are masked by other compounds.

    I suppose the question comes down to what the meaning of "pure" is....

    Hope this helps a bit...

    Rob Wallace
     
  7. Ed_McDonnell

    Ed_McDonnell

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    Rob - Thanks for the very informative response. It now appears that the objectionable smell is coming from some reaction between the tung oil and the natural oils in the wood that I was using it on. The odor of each of the tung oil and the wood alone is not objectionable, but put the two together and whhhoooooo!!!

    The other day I had the bad smell on my hands and when I sniffed the bottle, I must have really been smelling my hands. Today the oil in the bottle smells fine.

    I've never experienced anything like this before, but I've learned that the exotic woods we find from time to time in South Florida can surprise you in a lot of different ways.

    Ed
     
  8. MichaelMouse

    MichaelMouse

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    Not going to parse like Rob and Willie C. Pure is without additives, period.

    That said, tung is often "boiled" like linseed to begin/facilitate the polymerization process. For instance, http://www.sutherlandwelles.com/tungoil.htm describes a method which is meant to seem magical, but appears all too common. Imagine the odor will change a bit even to our poor primate noses, just as the incompletely cured walnut oils discussed in the other thread. Siccatives of various types may add their odor as well.

    Then there's the solvent which is used to reduce the viscosity of the partially polymerized oil. Anyone who's been around certain nationalities knows (nose?) that perfume can be used to mask or modify an odor. An aircraft full of Soviets returning from Cuba is a scent to remember. Even the "Morning" (Utro) perfume supplied by Aeroflot couldn't mask it. Mineral spirits is a blend of a lot of weights and forms of organic solvents, so that could certainly make a new and displeasing odor.

    I'm not fond of the odor of tung, preferring linseed, but if you smell raw versus boiled linseed, you'll also notice a difference.

    I'm sure he'll jump in at some time, but http://www.sydneywoodturners.com.au/site/articles/finishing/oils.html but Steve's done some research.
     
  9. David Somers

    David Somers

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    Ed,

    Be careful not to confuse Tung oil with the rarer and more expensive Tongue Oil. While I have never known Tongue Oil to go rancid, its "manufacture" can vary in quality affecting its odor.

    It is an ages old product going back to the dawn of woodworking. Like its companion product, nose oil, it is collected by putting the tongue (or proboscus) in a tongue press for several hours to extract the oils. The procedure is quite uncomfortable, yet lucrative for the donor. The oils cure with exposure to air, a fact we have all unwittingly experienced when we sleep with out mouths open for too long. That yucky coating on your tongue in the morning is actually Tongue Varnish, not fully cured yet of course, fortunately for us mouth breathers.

    Tongue oil odors are caused by the diets and mouth hygiene of those who are subjected to the tongue presses and can vary considerably as you might imagine.

    Check the spelling on the bottle.

    Dave
     
  10. waltben

    waltben

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    Real tung oil does not have an offensive odor. Even when it is old and getting thick it still isn't anything I wouldn't have in my home. You've obviously been sold something that needs to go back to the store!
     
  11. Ed_McDonnell

    Ed_McDonnell

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    Dave - Step away from the volcano!!! The fumes might be starting to have an effect!!!!! :D

    Ed
     
  12. Paul Engle

    Paul Engle

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    I had a girl friend in college that like the smell of diesel fuel where I worked part time at nite..... those were sommmmmeee nites.
     
  13. elaine

    elaine

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    I used organic, pure tung oil to finish a 100 year old wood floor and it is smelling terrible. I plan to scrub the floor with baking soda. Do you think this will do the trick? The smell is very sour and I suspect the tung oil is reacting with old urine from dogs and cats that have soiled the floor.
     
  14. Dave Roller

    Dave Roller

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    I agree. I just went out to the shop to get a whiff of the tung oil I have. It's a pint size (Hope's Pure Tung Oil) , and I'll bet it's 20 years old--sticker say it cost me $5.99. From smelling the pint can and from the little I put on my hands, I got no odor.

    I found it unacceptable for flat work, but I never threw it away. Now that some of you use it for turnings, I'll be considering it again.

    By the way, if the stuff goes rancid, mine surely has had the chance to do so.
     
  15. squirrel

    squirrel

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    I have the same experience: no odours in tung oil.
    I bought 5 liter at once (pure) and I heard that I must keep it as much as possible free from contact with oxygen to avoid that it becomes unusable... so I put marbles in my bottle to fill it up to the top.
    Why do you put solvent in it? To make the first layers thinner? To allow to penetrate deeper?
    And what solvent do you use?

    second:
    TONGUE oil!!!! I don't believe you! It is a joke.

    Squirrel
     
  16. bfwhitma

    bfwhitma

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    Tung Oil

    Not to beat a dead horse, but pure tung oil whatever age is not offensive to smell-it is nutty as stated above and not a petrochemical smell at all. Won't give sheen without petrochemical additives.
     
  17. Ed_McDonnell

    Ed_McDonnell

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    My experience (as indicated in my replies to this thread last year (above)) is that Tung Oil when mixed with some things can produce a really horrible stench. It reacted with something in a piece of wood (I think black acacia) and produced a stink that nearly drove me out of my shop.

    It could be that in Elaine's situation that the tung oil combined wth the animal urine that soaked into the floor (and whatever bacterial byproducts were in there) may be producing a high powered stench.

    I kind of doubt that baking soda will do much of anything to help. When I had the problem, the smell pretty much went away after a couple days and the oil dried. Fortunately I was able to stick the turning outside. Not an option available with the floor. I suppose you could always try a coat of clear shellac over the suspect area in an attempt to seal the wood after the oil has had time to dry.

    I hope you were planning on using something else on the floor besides just tung oil.

    Ed
     
  18. MichaelMouse

    MichaelMouse

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    I don't like the smell of tung oil, and I suppose there are others. It smells the same to me whether "pure," thinned with mineral spirits, or with thinner and resin and called "Danish" oil. I don't use it any more.

    It's entirely possible that chemicals present in the floor or produced by bacteria living on their new tung oil food could make a different smell. If it had anything to do with acidity, baking soda may help. It's an OLD post, but no followup to indicate if it helped. Nice surfactant like washing soda would have lifted the non-polymerized fraction I would think.

    There are a lot of noses out there, and they do react differently to the same odor based on their body chemistry and experience.
     
  19. elaine

    elaine

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    The tung oil has had 4 months to dry, so the smell is not going to dissipate on its own. The baking soda wash seemed to help a little, but the sour smell is back. It isn't as strong, but that might be a factor of the weather, too. I guess I will have to varnish the floor to seal it up. I used all green, safe chemicals on this project. The nasty smell is probably organic, too! Ugh. Thank you for your comments.
     

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