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 What causes cracksq
Author: leonardA 
Date:   2003-03-26 22:07

I've read a lot about wood instruments cracking. How does this usually happen? I could see that it might happen when you're putting the bell on the lower joint, if you press too hard. I could also see that with a sudden temperature change it could happen. Are there any other ways.

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 Re: What causes cracksq
Author: ctt489 
Date:   2003-03-26 22:17

Temperature changes - wood expands. Thats why keep your clarinet in a nice heavy protected case like the one I'm selling at [ Dammit. You're not that good. Don't try advertising here again. Mark C.]

oh I'm good.

But seriously you should not play a horn right from coming in from the cold. AND NEVER PLAY A WOOD HORN OUTSIDE - EVEN IN AZ,TX,CA or other.

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 Re: What causes cracksq
Author: Bradley 
Date:   2003-03-26 22:26

[ Please keep selling information between you two, not public. This is not an advertising forum.]

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 Re: What causes cracksq
Author: ctt489 
Date:   2003-03-26 22:31

[ Keep the chitchat to yourselves, please. Discussing items you're selling is not permitted.]

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 Re: What causes cracksq
Author: hans 
Date:   2003-03-27 01:24

Wood swells when it absorbs moisture and shrinks as it dries out and, like most materials, changes dimensions with temperature. If the changes are rapid and/or excessive, cracking is a likely result.
There is a comprehensive article about this at
and a search of this BB will no doubt provide many more.

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 Re: What causes cracksq
Author: Dee 
Date:   2003-03-27 01:32

If you look up the coefficient of thermal expansion of wood and calculate the stresses due solely to thermal expansion and contraction, the force is far too small to crack the wood. The changes in the dimensions are nearly indetectable. However hidden flaws in the wood could lead to cracking even with insignificant forces. If it has these flaws, even bumping it lightly could cause it to crack even if completely protected from temperature changes.

Humidity is an entirely different story. The fluctuation can cause major contraction and swelling of the wood to the point where the rings are loose enough to fall off. This degree of change could generate rather large stresses in the wood.

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 Re: What causes cracksq
Author: sfalexi 
Date:   2003-03-27 03:27

Just so you know, if you just bought a new wooden instrument or are planning (new, I don't think this applies to reconditioned), it's recommended to break in the instrument. Start out playing it only about fifteen minutes for the first few days, then a half hour, and work up gradually. I believe this is so the moisture from your breath isn't overwhelming the wood which has never delt with this moisture from the inside. It conditions the inside slowly, but surely. And if you want to take it even slower, that's all the better.

And I believe most wood is most susceptable to cracks within the first year or two. Hence the one or two year warranties you get. Of course it's possible to crack afterwards, but less likely.

And if you find a crack, you have to wait till it's big enough to pin shut. Just don't let it go all the way through the wood (keep it on the surface). I'm not sure whether this can be fixed or not, since I'm not a technician, but I'm sure that if it can, it's a much bigger pain than just a surface crack.


US Army Japan Band

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 Re: What causes cracksq
Author: Gordon (NZ) 
Date:   2003-03-27 10:37

"...you have to wait till it's big enough to pin shut."

IMHO: ......

Cracks are not pinned shut. Indeed, this would be setting the area up for cracking again in an even more highly-stressed location at the ends of the pins.

Pinning is done to STABILIZE the timber, so that a crack does not have a tendency to keep opening and shutting. Then , and only then, can the crack be reliably 'filled'.

This is particularly important if the crack goes through a tone hole, which is almost the norm. Otherwise, every time the crack opened up wider than the filling material the tone hole would leak.

If an unpinned crack were filled while it was in its most 'open' state, then when the timber dried and the timber shrank, there would be at least a strong theoretical possibility of the crack extending into the bore, greatly complicating the problems.

Even after pinning, the timber in the region of the crack can still move, affecting the width of the crack. This is because where the pins actually cross the crack they are quite deep within the timber, and do not have a complete effect in stabilizing the SURFACE of the timber.

Sometimes a crack is rather too narrow to be filled. It can be widened (to a shallow depth) with a minute circular saw (or other means) so that a filler has a chance of getting in, and so that the filler has sufficient width that there is more chance of it accommodating slight variations to the width of the crack. i.e. it is easier for a glue/filler to cope with a width change from 0.5 mm + or - 0.025 mm (10% change), a width change from 0.1 mm + or - 0.025 mm (50% change).

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 Re: What causes cracksq
Author: BobD 
Date:   2003-03-27 12:59

Dee wrote:
>If you look up the coefficient of thermal expansion of wood and calculate the stresses due solely to thermal expansion and contraction, the force is >far too small to crack the wood.

I believe your comments do have merit. I myself have never seen coefficients both longitudinal and transverse for the cured woods that are used for clarinets.
Thanks again,Gordon, for sharing your experience and expertise.

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 Re: What causes cracksq
Author: LBViola04 
Date:   2003-03-28 11:57

If you are worried about your instrument cracking, you can also buy something called a Dampit and put it in your case. It regulates moisture and helps the wood not to crack.

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