Shrinkage problem

Sean Cochran

Sean Cochran

Well-Known Member
No its not from jumping in cold water.:)
I noticed the last two knives Ive dont with wood scales after I brought them in from the shop the scales shrank just a little. It is enough for the tang to be just a little proud of the scales.
Both of these were with non stab wood (one was purpleheart the other was ebony). Both were oil finished (several coats) and hand rubbed with 0000 steel wool.
My first thought was the humidity difference from the shop to house, but the air is very dry outside right now so I would think the wood would swell some in the more humid house. Im at a loss.:confused: Any ideas?

Sean
 
Sean, I have gas heat and it's drier than a popcorn f@#T in here. I think it may be more humid in your shop.
 
I had the same problem. I finally figured out that the moisture left in the wood out in the shop was freezing and expanding during the winter. When I'd bring them into the house, they'd thaw and shrink a little bit. I noticed that if I finished them in the late spring, summer, or early fall, I didn't have this problem.

Jamie
 
Wood, Ivory and Stag can and will shrink.
I have put wood on a knife that had been slabed for 10 years and after a week you could feel the tang sticking up.
That's knifemaking.
 
polarbearforge said:
I had the same problem. I finally figured out that the moisture left in the wood out in the shop was freezing and expanding during the winter. When I'd bring them into the house, they'd thaw and shrink a little bit. I noticed that if I finished them in the late spring, summer, or early fall, I didn't have this problem.

Jamie
Click to expand...

I hadnt thought about that, my shop is only heated when Im in it. I dont have the problem any other time of the year, so Im am convinced it has something to due with the humidity, the wood is not just moving, it is uniformly shrinking. The tang is proud of the wood by the same amount all around the handle.

Sean
 
I had that happen with stabilized wood the other day. I'm pretty sure it's a moisture thing, but I don't know what to do about it.
 
Sean,
I can't help you with that knife, but I can help with future projects.
Call me tomorrow.
Del
 
I've even seen it happen a little with stabilized wood and even Micarta a very little. Our Kentucky weather changes so drastic. Makes great Bourbon though2thumbs

I wont use hardly any kind of wood that hasn't been stabilized anymore. Even if I have the wood very dry and build the knife in an air conditioned shop. Next thing you know I might have to ship the knife from 98% humidity and 90 degree Kentucky summer, or like right now 14 degrees and 68% humidity to Colarodo or Arizona where its certain to be hot and dry at some point.
 
I dont know if this will be a solution to your problem, but in my shop I keep all my handle material in a "dry box".

I made mine out of 2x2's and 1/4" plywood scrap.

The box is 4' tall x 3' wide x 2' deep. with a hinged lid on one side (think Army foot locker standing on end)

I put shelves of grating material about every 10" or so with vents in the top to allow air flow.

I put a light fixture with a Christmas light timer in line. Then installed a 100 watt bulb. I have the timer set to run 5 hours at a time, I run it full time if its really damp outside.

I lined the inside of mine with sheet foam insulation with the foil facing inside the box, dont know it this makes much of a difference, but I had it handy.

I store all but my stabilized handle material in this box. Ive been using it now for about 2 years and have had no problem with shrinkage or warpage. Plus it keeps the mice out of my antler!

Thanks and God Bless
Mike
 
Hey Sean,

I'll jump in on this one just because of 15 plus years as a working, licensed hardwood lumber inspector.

First, the ambient moisture content is lower in the winter than any other time of the year. It sounds wrong, but it's so. Usually between 2 and 4 % lower than in summer.

The reason I point this out is that the material you are using may have been dried, but not Kiln Dried. Especially common with the exotic materials from third world countries you mention. That's why they usually have wax covering it when you receive them. That means that it is always only going to be as dry as the moisture in the air around it. And I don't care if it's been air drying for 100 years. As it takes on moisture...it will swell. as it dries out...it will shrink. UNTIL...it's sealed throughly!

So that's why stabilizing is so good for reclaimed and none commercial natural products like old deer antler or that stump of walnut you dug out of the back yard and cut up to get the root burl.

The kiln drying process mechanically forces the moisture out of wood down to 5-7%. This collapses the cellular structure in wood and stabilizes it by reducing it's ability to absorb moisture without prolonged exposure. Kind of like a raisin. No matter how much moisture you add back to it...it's never going to be a grape again. ;~)

What's probably happening in your case is when you cut out your dimensional pieces, you expose more of a thinner cross section of the wood. It can then leach out more trapped moisture. You work the piece, mount it and the whole time it is shrinking. You bring it in during the winter and the moisture content is down already and the heating system is drying the air even further. As it dries, it continues to shrink further.

The simple fix is...cut your pieces long before you need um. Wax the end grain very well so they don't crack and then let them set for a while. Within a week or two you'll be able to actually measure a couple of hundredths of shrinkage. Then you can shape the pieces, soak um in you're favorite oil for 24 hours (I like natural danish oil) and finish um. Shouldn't shrink much further.

Or you can stick the pieces in a microwave on defrost for a few minutes. If you're crazy enough and have a very understanding wife. LOL

But be careful if you try to nuke um. Besides the stank in the house and risk of catastrophic fire, there is a good chance of cracking the wood if you go to far to fast. None of which are outcomes I want to risk devoice over. LOL

Good luck man. It's a pain when it happens. And it happens to most of us from time to time.
 
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