Dry heat vs. Heat gun using oil ?

[bentstick54]

On Osage in particular I have used dry heat,(heat gun) to make very minor corrections a few times. I have read that some use cooking oil along with a heat gun to help carry the heat into the wood more readily. Does using oil effect the wood in any negative way after correction is made. What happens to any oil staying inside the wood after the wood cools down. Will it soften the bending tendency of the wood itself in the long term? Say you heat 1 limb with only dry heat, and the other using oil, will the 2 limbs tiller out the same? Or will the limb with the added oil have a tendency to be “softer”?

[Badger]

The oil does not penetrate very deep into the wood, it stays right on the surface. Wood is only porous on the ends of a growth ring.

[Pat B]

I've used cooking oil with a heat gun for bending and correcting osage and other woods for many years without problems except trying too much of a bend. In those cases steam or boiling works best.

[PatM]

The oil does not penetrate very deep into the wood, it stays right on the surface. Wood is only porous on the ends of a growth ring.

 False.  Wood has structures for transporting from center to periphery.

[Badger]

The oil does not penetrate very deep into the wood, it stays right on the surface. Wood is only porous on the ends of a growth ring.

 False.  Wood has structures for transporting from center to periphery.

  What keeps wind barrels from leaking? I know they are all cut flat sawn with one ring running the length. I seriously doubt if it would go very deep.

[Badger]

 I was just reading that wood can transport through the sides but not the face of one growth ring, so it could absorb very small amounts into the sides but that would also be infinitesimal.

[Flyonline]

  What keeps wind barrels from leaking? I know they are all cut flat sawn with one ring running the length. I seriously doubt if it would go very deep.

Not quite true - french/european oak is split, american oak is sawn. I believe it has to do with the pore sizes, but first hand I know that american oak barrels leak a heck of a lot more through the wood than french. There is also significant transfer of moisture through the wood, I believe we work on 5% loss per year per barrel in ambient RH. I can go further, but it's outside this discussion on oil.

Back to the oil, I've wondered if it can inhibit finish application/longevity later on or does a final sand remove pretty well all of it?

[Dances with squirrels]

I have never, not once used oil to make heat corrections with a heat gun and have done it hundreds of times on a variety of bow woods. I try to use dry heat on dry wood, and steam or boiling on green wood... but haven't adhered to it 100%. Maybe I'm missing something. Why do some think oil is needed? What problem does it solve and how?

[hoosierf]

It helps with scorching. That’s the only reason I do it.

[PatM]

https://en.wikipedia.org/wiki/Medullary_ray_(botany)

  Oak is used for barrels because it has tyloses that relatively seal it.

[Pat B]

With proper prep, I've never had problems adding finish to a bow I've used oil and heat on, not just a finish, not rawhide and other soft backings and not sinew backing.

[Selfbowman]

I to don’t use oil in dry heat process. If you keep the heat gun moving enough it won’t scorch either.
Don’t know what’s right or wrong but that’s how I do it without problems. Now if you said it would prevent set I would be all over it. Arvin

[bassman]

For deep heat treat I used to use oil, but not any more. With a Mighty Mite heat gun I can get an even heat treat with out scorching the wood with no oil. I have heat treated Birch, Walnut,and Elm to the point were  the bow's back was hot to the touch, and repeat the process 2 or 3 times before the bow was finished. The backs have held up fine. Birch,and Walnut are low mass woods. Elm is pretty dense, so I can get the Birch, and Walnut limbs heat treated in shorter order. The bows I made this way were 35 to 45 lb bows with 25.5 inch draw length tillered to 26 inches. May be why the backs are holding up just fine, and it sure feels like the heat is penetrating from front to back, but I will let you guys decide that. I know I am building better bows because of it.

[bentstick54]

Thanks for all your thoughts. It sounds like both schools of thought work, but whether or not there is a real advantage to using oil as part of the process is questionable. It sounds like it won’t hurt anything, but maybe there is no great benefit.

[paulsemp]

I like using oil. I personally believe it helps the heat dig deeper before you scorch. I think you get a deeper temper out of it.