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Thread: Tung Oil Smell

  1. #1
    Join Date
    Jul 2006
    Location
    South Florida
    Posts
    636

    Default Tung Oil Smell

    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. #2
    Join Date
    Jun 2004
    Location
    Cumberland
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    229

    Default 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. #3
    Join Date
    Jan 2006
    Location
    Northern Virginia
    Posts
    16

    Default

    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
    Scott Hurley

    llth Commandment: Thou shalt not covet thy neighbor's new lathe

  4. #4

    Default 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
    Don McIvor
    Twisp, WA

  5. #5
    Join Date
    Jul 2006
    Location
    South Florida
    Posts
    636

    Default

    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. #6
    Join Date
    Jun 2004
    Location
    Ames, Iowa (about 25 miles north of Des Moines)
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    770

    Default 100% Pure?

    Quote Originally Posted by Ed_McDonnell
    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
    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
    Rob Wallace

    Ames, Iowa
    President, Ames Area Woodturners
    Member, Board of Directors - American Association of Woodturners - rob@woodturner.org
    Member, Des Moines Woodturners
    Vice-President, Board of Trustees, Octagon Center for the Arts, Ames, Iowa - www.octagonarts.org
    My Woodturning Gallery -- Rob Wallace's Homepage - Find Me on Facebook
    Woodturners: Check out my Woodturning Links Web Page - http://www.public.iastate.edu/~rwallace/WTlinks.html

  7. #7
    Join Date
    Jul 2006
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    South Florida
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    Default

    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. #8

    Default

    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/...hing/oils.html but Steve's done some research.
    Stand clear, rest near, and cut the wood as it wishes to be cut.

  9. #9
    Join Date
    Aug 2005
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    Ballard (Seattle) WA and Volcano, Hawaii....on top of Kilauea Volcano
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    Default

    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
    Dave Somers
    Ballard (Seattle), WA and Volcano, HI

  10. #10

    Default

    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!
    Walt Bennett
    http://www.abhats.com

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