Heating wood in oil?

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Re: Heating wood in oil?

Postby ericgoodson » Fri Aug 09, 2013 11:20 am

see below...
Last edited by ericgoodson on Fri Aug 09, 2013 11:31 am, edited 2 times in total.
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Re: Heating wood in oil?

Postby ericgoodson » Fri Aug 09, 2013 11:30 am

GREAT questions, TonyH! The seasonal movement and drying distortion questions are really interesting. I can say that one of the blanks that I fired was dead green, straight from a freshly cut sapling. It did not crack, was fully penetrated by oil, and did not come out green. Some of the bubbles that rose to the top of the oil during firing were decidedly green in color! We will see how that piece behaves in the coming weeks.
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Re: Heating wood in oil?

Postby DavidFisher » Fri Aug 09, 2013 1:18 pm

This has been very enlightening, Eric. I appreciate you sharing your experiment. I have noticed that heat and soaking definitely aid in penetration and protection of spoons and bowls, although I have never tried the crock pot method. For bowls too large for a crock pot, the sun can be a great heater. A bowl slathered with oil will heat up quite hot on a sunny day, and more oil can be applied as it is absorbed. In the winter, a light bulb kiln or a wood stove does a good job too (I don't put the bowl IN the wood stove!)

What is most intriguing to me is the idea of the oil driving out the moisture from green wood. In the case of your turned bowls, this would seem to eliminate the opportunity for them to crack while drying. I wonder if there would be any differences in appearance, protection, etc. between two otherwise similar items if one were given this treatment after drying and the other green?
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Re: Heating wood in oil?

Postby gavin » Sat Aug 10, 2013 9:38 am

ericgoodson wrote:Is there a place on this site where people who are geographically close can get in contact?

You declare via User Control Panel where in the world you are. Then any person near you can get in touch with you. Also consider identifying any local group near you - there are many in UK. If you are in N America or Baluchistan - well, I don't know of any - but you should start one. Especially you should start one if you doubt your skills are good enough and you can be honest with folk that your skill level is whatever it is - for your skills soon will improve.

About 8 years ago I started Shed Therapy - a monthly drop-in woodworking session. Some weeks no one came. Now I turn them away once I get to 10 persons booking by e mail. It used to be free ,but now I seek a donation for use of material, and of my tools. My counsel is : Create a local group - if you have not got one. Appear with your bowl or spindle pole lathe at local public shows & events and put out publicity you are going to next meet next at Y place at X date and Z time and ask people to bring hand-powered tools. See what happens - trust me , good things will follow.

Do take action on this now. The summer will be gone soon - if you are in Northern Hemisphere and with it your chance to recruit like-minded persons. Which show in the next 2 weeks is it feasible you take your bowl lathe to?

You have demonstrated you can make a bowl. Seeing another made in a public place will fascinate some folk. They will have no interest in the quality of yours - they'll have VAST interest that it is clearly feasible, and they'll know they could do the same. They'll get you have only turned a few, but some of them will be dead interested.

Go forth and multiply!! And please report back, for your experience will empower others to do likewise. :D
Trust me, there is more fun than you can poke a stick at here. Community is built, social relationships created and strengthened, knowledge and culture transmitted over generations. And for some, ware will be sold and a sense of self-worth added to. It does need you Eric to take first step.
Gavin Phillips


- teacher, demonstrator & supporter of greenwoodworking & human-powered turning
- Supplier of Fun & Confidence

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Re: Heating wood in oil?

Postby ericgoodson » Sun Aug 11, 2013 12:24 pm

More (and more dramatic) results to report:
My eldest daughter was turning eight yesterday, and had been asking for her own special bowl like what Mommy and her sister have. So on Friday night I set about turning her a little kuksa out of relatively green maple. The wood cut wonderfully and even spun moisture out the ends during turning. Definitely green wood.
Emboldened by my recent experiments, on Saturday I put that new bowl into a mixture of linseed and beeswax, along with an older bowl that had already air dried. I cooked them both for eight hours and they reached a max temp of about 270F.
The results:
As you can see, cracks emerged in the end grain and the edge distorted pretty significantly in the green bowl. Live and learn. I will probably try to repair with epoxy.
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Re: Heating wood in oil?

Postby ericgoodson » Sun Aug 11, 2013 12:48 pm

Besides cracking the green wood, the oil/wax cooking also had an interesting impact on the dry bowl. Below is a shot of two bowls made from the same spalted birch. The one on the right has been simply soaked in oil for a few days. The one on the left was cooked in the oil/wax bath. It turned much darker than the other bowl, and did seem to warp more along the rim than the other.
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Re: Heating wood in oil?

Postby DavidFisher » Tue Aug 13, 2013 2:39 pm

Hmmm. Thanks for sharing the unfortunate results on your daughter's bowl, Eric. It would seem that, whether in oil or in air, fast drying may not be the best thing for a bowl. However, as you mentioned, Dan Dustin uses this method quite successfully for spoons. Maybe the key difference is that a spoon is thinner and more able to move as it dries than a bowl?
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Re: Heating wood in oil?

Postby ToneWood » Sun Aug 18, 2013 6:08 am

Interesting thread. Personally, I wouldn't use epoxy on anything somebody might eat from.
ericgoodson wrote:... If drying oil polymerizes and bonds chemically with the wood through oxidation, you are not just protecting the wood, you are changing it into a different substance, the result being stronger and more rigid (and noticeably heavier) than normal wood. I have soaked some spoons and kuksa's in oil for a few weeks, and after curing they do behave differently than wood that has been more quickly treated. They repel water better and seem stronger...

You raise several interesting points above:
a. Will oil that has soaked into the wood polymerize, like oil on the surface? As it is not exposed to air, perhaps not or perhaps differently.
b. Does polymerized oil bond chemically with the wood? I had previously assumed not but, upon reflection, it certainly might do.
c. "seem stronger" - in what way? Is it just the increased weight that gives this impression?

I recently came across at least 2 references to old objects (1930s toy figurines in one case and a fancy case/box in the other) being moulded using sawdust & linseed oil (+ other ingredients that I don't recall) in what appears to be precursor to modern plastics. It did make me wonder if the linseed oil might have been used as a crude/cheap, early polymer (i.e. plastic)/adhesive. [The early synthetic plastic Bakelite had already been invented/discovered back in 1907.] Interestingly, despite their humble ingredients, both objects are now valuable.
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Re: Heating wood in oil?

Postby ericgoodson » Tue Oct 29, 2013 3:45 pm

Hi ToneWood,
Sorry I did not reply earlier.
I think you might be right about my "feels stronger" statement. It is probably all about the weight of the wood.
I like your point about whether oil in the center of the wood will polymerize, especially since it is not exposed to air. I wonder if it is just sitting in there, in suspended animation... I could always "fire" a bit of wood, let it sit for a few months, and then cut it open to see if the interior is still oily... Maybe an experiment for another day.
My understanding is that the oil does indeed bond chemically with the wood. I looked it up in a few places and it seems to be true.
Thanks again,
Eric
"Use it up, wear it out, make it do, or do without."
--New England proverb
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Re: Heating wood in oil?

Postby ericgoodson » Tue Oct 29, 2013 3:51 pm

Hey David,
Given the size of your bowls, a crock pot might not work. But how about a turkey frier? They can get pretty big, and have precise temp controls!

I am definitely finding that the wood darkens pretty significantly in this process, which I am not liking. For my latest I just dipped the bowl in 140degree walnut oil/beeswax for five minutes. The air bubbles coming out of the bowl indicated the oil was penetrating. The wood did not discolor. It is no where near as heavy either.

Oh, and for those of you out there who use milk paints, the firing does not seem to cook the paint off. However, if you are layering one paint color over another, the firing process seems to sort of merge the colors together, with the bottom color tainting the top color.
"Use it up, wear it out, make it do, or do without."
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