Tung Oil Tree

[Paul M. Kaplowitz]

Having been a port ( Charleston, SC ) for the last 400 years, we have trees from all over the world. I have turned Chinaberry, Chinese Tallow, Mimosa, Camphor and several others. Yesterday I got a new one. Tung Oil Tree (Aleurites Fordii ). I know the nuts are very poisonous, but what about the wood? Anyone have any knowledge about turning and use of the wood?

 

[Rob Wallace]

Potentially toxic

Hi Paul!

Given that this species is a member of the Spurge Family (Euphorbiaceae) I certainly would treat the wood as suspect and potentially toxic.

One web site reports that "All parts of tung tree are toxic, but the fruits are most dangerous." [q.v. http://www.floridata.com/ref/a/aleu_for.cfm ]

There is a wide range of secondary chemical compounds found in members of the Euphorbiaceae that can cause severe contact dermatitis and tissue damage. African species of Euphorbia have been known to cause blindness, skin blistering, and even death when the toxic latex comes in contact with people. I get a call from local hospitals every few years from emergency room physicians who need to treat patients who have euphorbia latex poisoning of some sort (....including poinsettia!). While the wood is not likely to contain latex, per se, it is likely that the toxic compounds will be found at least in some concentration in the wood.

If you do decide to turn it, work with it as you would any potentially toxic species, and proceed at your own risk.... (e.g. cover skin, full respiratory protection, proper disposal of wood scraps and dust, etc.)

Rob

 

[Hu Lowery]

Interesting

Hi Paul!

Given that this species is a member of the Spurge Family (Euphorbiaceae) I certainly would treat the wood as suspect and potentially toxic.

One web site reports that "All parts of tung tree are toxic, but the fruits are most dangerous." [q.v. http://www.floridata.com/ref/a/aleu_for.cfm ]

There is a wide range of secondary chemical compounds found in members of the Euphorbiaceae that can cause severe contact dermatitis and tissue damage. African species of Euphorbia have been known to cause blindness, skin blistering, and even death when the toxic latex comes in contact with people. I get a call from local hospitals every few years from emergency room physicians who need to treat patients who have euphorbia latex poisoning of some sort (....including poinsettia!). While the wood is not likely to contain latex, per se, it is likely that the toxic compounds will be found at least in some concentration in the wood.

If you do decide to turn it, work with it as you would any potentially toxic species, and proceed at your own risk.... (e.g. cover skin, full respiratory protection, proper disposal of wood scraps and dust, etc.)

Rob

Rob,

Interesting and good to know that tung oil trees are dangerous. When I was small there were still some large groves of tung oil trees growing in the area from the days that tung oil was not only being used to finish wood but was the wonder drug that was going to cure all ailments. Huge groves were planted in the belief that the growers were going to get wealthy due to the medical demand for tung oil. We still have a few trees on fence rows and in the occasional yard but the last of the commercial groves I knew of were ripped out to plant row crops long before I was an adult. People now ask what they are when they see a tree.

A good reminder to check properties when turning a less common wood. Some of the common ones too!

Hu

 

[dickhob]

If the tung tree is so toxic, how is it that tung oil- from the nuts and leaves is used as a common finish in food utensils and is FDA approved?

Check out this link- http://www.realmilkpaint.com/oil.html
Thanks
Dick

 

[Rob Wallace]

Dick:

When processing plant-derived oils, there are several steps involved with cleaning and purification of the oil once it is extracted from the plant part(s). The oil is subject to different kinds of processing which involves filtering, raising the temperature in oxygen-free environments (to form polymerized tung oil), and to clarify it with either adsorption (charcoal or other adsorbants), or chemical-reacted precipitation. During these processes, many of the contaminating toxic substances are removed. Despite these processes, it can be assumed that there still are contaminants in the liquid ("uncured") tung oil, that could cause reactions in sensitive individuals. Fortunately, people don't consume tung oil directly, and because it is a "drying" oil (one that auto-oxidizes and cross-links into 'cured' films), the risk of ingesting the low levels of any residual toxins from treated wooden utensils is quite small.

The same thing could be said for cottonseed oil, which is a cooking oil used in some food materials such as mayonnaise and salad dressing; the toxic substance gossypol is removed during processing to render the oil safe for consumption.

Rob Wallace

 

[Bill Boehme]

The same thing could be said for cottonseed oil, which is a cooking oil used in some food materials such as mayonnaise and salad dressing; the toxic substance gossypol is removed during processing to render the oil safe for consumption.

Rob Wallace

When my dad was a kid and they took their cotton to the gin, they would then take the seeds to a press where the oil was squeezed out. They would then use the cottonseed oil for cooking and the pulverized seeds were fed to the cows.

I suppose that the oil still had toxins since the only processing was squeezing and filtering. Even though the cotton gin hs been closed for most of my life, everything is still standing and my dad showed me the place where the oil was extracted from the seeds.

 

[Rob Wallace]

Bill:

After reading at least 10 or 12 term papers on cottonseed oil processing over the past 18 years written by students in my Economic Botany class, I am quite familiar with the processing of these seeds, but don't consider myself any kind of expert or specialist on the topic.

The toxin, gossypol apparently can be degraded by the microbial flora in the cattle's gut, rendering it non-toxic and digestible. Feeding the seed meal to cows and other ruminant livestock has been going on for a very long time, without ill effects.

I agree there was probably some toxin in the oil since it was only cold-pressed and filtered, however the act of cooking with it at high temperature may also rendered the gossypol (a complex phenolic compound) less toxic through thermal degradation. I certainly would not want to cook with it on a regular basis unless I knew the toxin was "de-toxed" before consumption.

Cotton is the #1 fiber crop in the world, but few know about its oil or meal components as also being highly useful secondary crops from the same plant.

Rob

 

[MichaelMouse]

Cottonseed cake makes great catfish bait. Think the residual oils are what attracts 'em.

 

[Greg Keddy]

Dick:
. Fortunately, people don't consume tung oil directly, and because it is a "drying" oil (one that auto-oxidizes and cross-links into 'cured' films),

Rob Wallace

Does tung oil actually crosslink? Or it it more of an entanglement?

 

[Rob Wallace]

Greg:

My understanding is that the so-called "drying" oils (e.g. tung, linseed, walnut) cure by incorporating oxygen into a cross-linking structure between the fatty acids by using their double bonds to cause the oxygen to bridge [cross-link] between adjacent fatty acids. Those oils which do this have fatty acid compositions that are particularly high in number of double bonds (highly unsaturated), which are attacked by the highly reactive oxygen that bonds readily to the fatty acids at the double bond sites.

Thus, "curing" in these instances is not polymerization or true drying (as seen in evaporative finishes like shellac & lacquer where the solvent evaporates, leaving the solids), but is crosslinking with the addition of oxygen. [BTW, this reaction is exothermic, which is what causes the spontaneous combustion reported in the "oily rag" scenarios you read about in woodworking publications.]

An acceptable explantion on Wikipedia can be found HERE: http://en.wikipedia.org/wiki/Drying_oil

I'm not sure what you mean by 'entanglement'; clearly a 3-dimensional matrix of cross-linked molecules develops, so if that's what you mean by entanglement, then yes.

Hope this helps,

Rob

 

[Bill Boehme]

Does tung oil actually crosslink? Or it it more of an entanglement?

An entanglement is what leads to the need for a politician to "reinvent" himself. Sometimes cross-linking may be involved. 😀

 

[Mark Mandell]

An entanglement is what leads to the need for a politician to "reinvent" himself. Sometimes cross-linking may be involved. 😀

"Cross-linking" is pretty common and doesn't create much fuss. But cross-dressing? That gets'em every time. 🙄

 

[Bill Boehme]

"Cross-linking" is pretty common and doesn't create much fuss. But cross-dressing? That gets'em every time. 🙄

How about un-dressing? I seem to recall that some politician thought it was a good idea to go hiking au naturel, perhaps to get closer to nature. Lesson to be learned is that "good" and "smart" are not equivalent.

 

[Greg Keddy]

Greg:

My understanding is that the so-called "drying" oils (e.g. tung, linseed, walnut) cure by incorporating oxygen into a cross-linking structure between the fatty acids by using their double bonds to cause the oxygen to bridge [cross-link] between adjacent fatty acids. Those oils which do this have fatty acid compositions that are particularly high in number of double bonds (highly unsaturated), which are attacked by the highly reactive oxygen that bonds readily to the fatty acids at the double bond sites.

Thus, "curing" in these instances is not polymerization or true drying (as seen in evaporative finishes like shellac & lacquer where the solvent evaporates, leaving the solids), but is crosslinking with the addition of oxygen. [BTW, this reaction is exothermic, which is what causes the spontaneous combustion reported in the "oily rag" scenarios you read about in woodworking publications.]

An acceptable explantion on Wikipedia can be found HERE: http://en.wikipedia.org/wiki/Drying_oil

I'm not sure what you mean by 'entanglement'; clearly a 3-dimensional matrix of cross-linked molecules develops, so if that's what you mean by entanglement, then yes.

Hope this helps,

Rob

Thanks for the explanation Rob. I'm referring to polymer entanglement which is when long chains wrap around each other creating a sort of pseudo cross link that is a physical connection rather than a chemical bond

I don't remember the name of the naked hiking politician but I remember Anthony Weiner getting in trouble for something, now if I could just remember what...

 

[dickhob]

Rob,
Thanks for clearing that up for me.
Dick

 

[Bill Boehme]

Thanks for the explanation Rob. I'm referring to polymer entanglement which is when long chains wrap around each other creating a sort of pseudo cross link that is a physical connection rather than a chemical bond ...

I believe that you are assuming some similarity between tung oil and motor oils that does not exist. Modern motor oils are synthesized to have long molecular chains in order to give them greater film strength under extreme high pressure-temperature conditions such as would be the case between cylinder walls and piston rings and between valve stems and guides.

Motor oil "wears out" as these long molecules break into shorter pieces. Other things like build up of acids also contribute to the oil wearing out. The acids come from blow-by gasses, oxygen, water, and metallic contaminants. Many years ago tetraethyl lead was eliminated from gasoline and that reduced the problem of acids considerably.

With tung oil, based on my understanding of what Rob described, I don't believe that there are long molecular chains nor do I see a mechanism that would cause the "entanglement" you envision to occur even if such molecular chains existed.