Why did this wood crack?

Hengelo_77

Hengelo_77

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Mar 2, 2006
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I've had the handle block with the tang hole cut laying in my workshop for at least two years.
The temperature goes with the seasons.
Last week I epoxied the tang in the block. I filled it up all the way, insered the tang, clamped as in the picture and put it on top of a radiator in the house to let the epoxy harden warm.
I estemate my shop to be 40F and inside the house 75F.
The wood was sold to me as Rosewood and looks simular to Bahia Rosewood I have.

First I thought it might have been the epoxy expanding while hardening, but it looks like the crack goes from the back towards the middle.

What happened?

(lemons/lemonade, I'm thinking of roughly finishing the knife and testing the blade to destruction)

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I would say the heat from the radiator is what caused it. I've got an old hand carved hard wood table that was my fathers my wife put an electric heater on top and it warped the top pretty bad. The table is over 42 years old the top is about 16" diameter and 1.5" thick.
 
I agree with heat being the likely cause of the crack.

I would try repairing the handle with thin cyanoacrylate before destroying the knife. Wick the crack full of adhesive and lightly clamp until dry.

Chuck
 
Thnx for the replies.
Assuming it was the heat, would it have cracked if the knife was finished and taken from the cold outside in to a warm livingroom?
 
Hengelo_77 said:
Thnx for the replies.
Assuming it was the heat, would it have cracked if the knife was finished and taken from the cold outside in to a warm livingroom?
Click to expand...

I don't think so. It wasn't the temperature change that cracked it, it was the temperature difference from one side to the other. Whichever side that was down to the radiator wanted to expand, and the side that was up didn't want to expand as much.

Just coming in from outside, the entire block warms up at a similar rate, and rather slowly at that.
 
I would guess the uneven heating (like kuraki mentions) and the quick extreme change in heat were the culprits. Your radiator that you set it on is also much hotter than 75 degrees. It has to be to heat the air in the room to 75. I sit in front of the fan on our gas fireplace and the air coming out if it has to be over 100 degrees f. I bet your radiator is that or more.

I think you should try filling the cracks with CA like chuck mentions. Also, it is only wood, You could cut the handle off and put another on if it doesn't work.
 
What they said^^^ the epoxy may have expanded as well. But an uneven heat, and a DRY heat from a radiator is most likely why it cracked!.. Most epoxies will cure fine at 70 and up
 
Alpha Knife Supply said:
I agree with heat being the likely cause of the crack.

I would try repairing the handle with thin cyanoacrylate before destroying the knife. Wick the crack full of adhesive and lightly clamp until dry.

Chuck
Click to expand...

This has worked for me too, but lately I’ve had good results with the gorilla polyurethane expanding glue for this type of repair. I just re-attached a headstock on a guitar this way, with the expanding glue.
 
You had a war going on in that wood. The epoxy can generate one temperature, you have the temperature of the wood and then the radiator heat attacking the wood.

That is a lot going on to that wood.
 
So too much direct heat?
Having the knife in that room during the epoxy stage but 2 or 3 feet away from the radiator would have been fine?
 
I had a sad experience with a piece of furniture from Hong Kong then shipped to NYC ! Apparently drier winter air in NYC ! Saved some pieces of mahogany the rest went to the wood stove.
Try to understand the history of the wood .What you never see may have a devastating effect on the wood . There was a serious problem with woodwinds like clarinets .In the making of the instruments the wood shattered on the lathe. They found that underbrush was burned near the trees that induced stresses that tore apart the wood when worked. Stock makers sometimes bring a piece of walnut to a kiln and the kiln operator throws the 2" thick walnut in with 1" wood .With a 2" The saved piece given a 1" schedule the 2" will warp and crack. Think of the wood as a live thing , temperature , time , humidity all play a part. The sight of 1/4" cracks in a fine piece of furniture was a very sad experience ! The saved mahogany was mixed with some hard maple and made a fine table
You might let your wood sit in a area that has stable conditions for some time then try the epoxy procedure.
 
I don’t apply direct (or close to it) heat to my handles when I’m epoxying it all together. I set up a temporary work space inside the house, get everything where it needs to go and then just leave the knife and handle on the counter overnight. Inside temps at my house are just fine. If you’re concerned that the temp won’t give the epoxy what it needs, try this: Leave the left over epoxy in whatever little mixing cup and set it by the knife. If it isn’t set up the next day like it should be, you’re pretty well guaranteed the knife handle isn’t going to be epoxied on very well... If it set up nicely, chances are the stuff inside the handle did just fine. Like the others have said, changes in temperature to wood can be a bad thing, particularly if it’s quick. Garage to radiator would qualify as quick, I’d imagine. Give those cracks a try with some thin super glue and see where you get. Hope it all turns out well-good looking knife you’ve got there.

Jeremy
 
heat combined with the nature of that piece.

That is brazilian tulipwood, a true rosewood, The heartwood is dense and very oily, it is slow to expand or contract and must be dryed very slowly.

The sapwood is much more like maple or mango, its softer, low in oil and thus expands and contracts much more rapidly. That would make a much greater stressed area on that piece.
 
Ambient temperature has far less effect on the moisture content of wood than relative humidity does. How humid is it in the shop? Merely having the wood around for 2 years is no guarantee that it is dry. That's why a moisture meter can be a good investment. Bringing a wood block of unknown moisture content into a dry house and putting it on a radiator, it would have been a miracle if it didn't check. It would have been a risk even if the block was dry. The crack is properly called a check, it is on a radius line to the center of the tree as most checks are, and is a result of the wood losing moisture too rapidly, unevenly, or otherwise being over-stressed while drying. It is possible that the block shrank a bit around the unyielding tang and epoxy and split as a result, but more likely that the heat caused rapid uneven drying
 
Mahoney said:
Ambient temperature has far less effect on the moisture content of wood than relative humidity does. How humid is it in the shop? Merely having the wood around for 2 years is no guarantee that it is dry. That's why a moisture meter can be a good investment.
Click to expand...

I thought moisture meters weren't very accurate on smaller pieces of wood and below about 10% moisture content? Not disagreeing about your advice at all, just curious.
 
Just an opinion from a novice.

It’s wood, wood has flaws, flaws add character. Unless it’s a commissioned piece, show piece piece or the flaw is highly susceptible, stabilize as best you can and finish it out. You might be surprised what you end up with.

Mike
 
Pinless meters can read moisture in small pieces and offer better accuracy at low moisture levels. $300-400 will buy a top of the line moisture meter. $200 will get you one that will do the job, and if you can live with pin marks and a bit less accuracy you can get one for $100. A meter is an investment, but depending on what you are paying for the handle blocks it can eventually pay for itself if it keeps you from buying or using wet wood
 
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