Re-hydrating a Very Dry Bow Stave?

toxophileken
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toxophileken
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July 10th, 2018, 11:11 pm #1

I know this has been discussed before, but I thought I'd reintroduce the topic.

I have a very dried out, but otherwise high quality yew stave that was given to me by a friend.  It feels super light compared to what it should for its ring count.  It has been stored in a very dry place (garage in the desert, not mine) for years.

Any thoughts on, first, is it possible to successfully rehydrate a stave like this; and, second, best method.

Not any sort of emergency, but I'm hoping Tim Baker or Steve Gardener (among others) will chime in.

I've been contemplating tying some weights to it and sinking it in the pool for a couple days or a week, then storing it in my controlled humidity wood shed to re-stabilize it at a more reasonable moisture content.

My guess is that chance of bacterial decay is slight, due to the nature of yew and how dry it was where it was stored.  I believe I have heard Tim talk about wood cells being collapsed and so damaged as to be unrecoverable as bow wood, but I could be remembering incorrectly...

Ken
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George Tsoukalas
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July 19th, 2018, 12:47 pm #2

Ken, how do you know it is dry? Did you test with a moisture meter?
My meter just tests the outside of the wood so I keep testing as I work the wood.
Jawge
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Nomad1
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July 20th, 2018, 5:14 am #3

I have a 5 foot limb of mtn ash thats been drying for the last 7 years I keep saying I will get to it but its still sitting their waiting I know it will make a great bow I see that bow every time I look at that bit of ash sitting in my shed...
http://nomadsurvival.tk/forum/
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French Crow
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July 23rd, 2018, 7:47 am #4

I don't think that the "super light feeling" is related to the water content: it makes a difference of only maybe 7%, right?
Maybe the wood cells have been damaged. Anyway the wood will be back to an equilibrium. A small section sample will rehydrate quickly and could be tested.
Bruno
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toxophileken
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July 25th, 2018, 3:02 am #5

George, stave has been stored in an extremely dry, hot place for years - long enough to have reached equilibrium with the environment.

Bruno, what, you don't think I can tell a 7% difference by feel?  I'm wounded!  Ha ha.  Just kidding...

Ken
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George Tsoukalas
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July 26th, 2018, 1:27 pm #6

Ken, if it has reached equilibrium so will the bow you make even if you rehydrate. Jawge
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toxophileken
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July 26th, 2018, 10:45 pm #7

George, if I understand what you are saying, if I rehydrate, I won't store it under the conditions it was stored in before it was gifted to me, so that isn't an issue.

The question is, will rehydrating it work, as far as getting it be be a bow.  I thought it would be an interesting discussion.  Of course, the easiest way for me to find out is to experiment...

Ken
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George Tsoukalas
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July 27th, 2018, 1:21 am #8

Oh I see, Ken. I've never tried to rehydrate a stave. I've always tried to keep moisture away.
Jawge
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toxophileken
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July 28th, 2018, 11:30 pm #9

Thanks, George.

I think what I will do is cut wedges off of both limbs, from the belly, going towards getting the limbs shaped correctly, thickness-wise.

Then, I will cut them in half, giving me four samples.  One sample I will submerge in our swimming pool, tied to a weight.  Another sample, I will put in my wood storage shed, where I run a swamp cooler to control the humidity and temperature.  The first sample will join the second after a week or so in the pool.  A third sample will be the control sample, which will be tested as is.  

Any suggestions for the fourth sample (or an other part of the test)?

Once the samples are at a more reasonable MC, I will try and figure out how to do a controlled test, probably making mini bows out of them.

Ken
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Brian T
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July 31st, 2018, 2:29 am #10

Water in wood is in two places : free water in the hollow volumes of the cells.
Bound water which is H-bonded to the cell wall materials of the wood structure.

Outdoors, under cover and not cooked in a shed, the equilibrium moisture content should run in the neighborhood of 12 - 14%
However, you have wood which has been kept super dry for years.  
That implies that some of the bound water has probably been lost as well.
No amount of soaking can put water molecules back in the exact places from which they were lost.

I'll suggest that wet steam will move the water faster than any passive treatment.
I don't know to what standard you can use to measure changes (improvements?) 
in the Modulus of Elasticity as your process continues.
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toxophileken
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July 31st, 2018, 3:13 am #11

Very good info.  I'm glad I reposted this old question!

On the samples, I will probably just make mini bows, and assess any breakages.  Of course, a mini bow will be under far less stress than a normal bow.  I guess I can make them more heavy than I normally make mini bows...

No hurry on this stave.  It can rehydrate for years as far as I'm concerned.  Right now I am having trouble with numb hands, so very little bow making going on.

This is making me want to accelerate my plans to acquire a microscope.  I already planned on getting one for examining grain structure in steel I heat treat.

Ken
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Brian T
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July 31st, 2018, 11:06 pm #12

Local paleo bow remnants from my mid western childhood locations were mostly green ash (Fraxinus pennsylvanica var subintegerrima.)
Ring porous, the staves were split out of a log to function much as a multiple leaf spring.
They must have worked quickly as that stuff goes from cheese to bone as it dries.
Maybe those were mechanical advantages that they discovered.

Microscopes.  From time to time, educational institutions have to replace one to several biology laboratories of compound microscopes.
The stage drives and the focus gear train drives just wear down and get sloppy.
You might find a surplus disposal sale with 10 - 60 microscopes for sale.

I have a whole career interest in wood anatomy and a collection of microscope slides of more than 300 species,
most of which are of commercial (and sometimes legal) importance.
I can manage very well with 100X or 400X maximum to see all I need for ID, etc.
Can't imagine the mag you'd need for steel.  Etched surfaces?
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toxophileken
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July 31st, 2018, 11:17 pm #13

Thanks for the additional info!

Probably etched, I'd imagine.  I have some feelers out for info about what I'd need for steel.  Steel examination would be the first priority, with wood examination being secondary.

Ken
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