[Woodcarver] Why is birch stable?

[Merrilee Johnson]

Well, now I know the whole reason my pine cupboard doors stick out in the 
winter and fit fine in the summer! With what you said then, there really 
isn't anything you can do to stop the movement but just compensate for it. I 
kept thinking if I sealed them again then  it wouldn't do all that moving! 
Now I'm glad I procrastinate things!   Thanks for the explaination.
Merrilee


>From: "Joe Dillett" <jdillett at thecarvingshop.com>
>Reply-To: "[Woodcarver]" <woodcarver at six.pairlist.net>
>To: "Joe Dillett (List)" <woodcarver at six.pairlist.net>
>Subject: [Woodcarver] Why is birch stable?
>Date: Sat, 6 Mar 2004 08:28:24 -0600
>
>To make a DONATION to the List using PayPal OR regular mail, click this 
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>Hopefully this won't be asked and answered in the following emails from
>earlier this week but... what do you mean ... "how stable is it (the
>wood)... ? Thanks for explaining
>Merrilee
>
>****************
>
>Hi Merrilee,
>
>Here in the Midwest U.S.A. a piece of wood that is sealed, like your 
>cabinet
>doors, will change +/- 3.5% moisture from summer to winter. This moisture
>change causes the physical size of the wood to change in width and 
>thickness
>but not in length. That why some of your doors stick in the summer and work
>fine in the winter. Different orientation of the grain also has an effect 
>on
>how much the size of the wood will change from season to season. Birch, 
>like
>most hard woods, changes more than softwoods. A 12-inch wide birch board
>that is quarter sawn will change .22 of an inch from summer to winter. That
>mean if you cut a dry birch board to exactly 12-inches wide in the winter
>that in the summer it will be about ¼ of an inch larger in width. This is
>because the fibers take on moisture and enlarge so just the width and
>thickness of the board change, not the length.
>
>What makes birch so different is that its size change is about the same
>percentage from length to width, where most wood changes about twice the
>rate in the flat grain (plain sawn) as it does in the perpendicular grain
>(quarter sawn) direction. This means less cupping problems with birch than
>with a wood like oak.
>
>For that +/-3.5% moisture change, a 12-inch wide board will change:
>
>Birch quarter sawn (Radial expansion) is .22-inch and plain sawn 
>(tangential
>expansion is .28-inch.
>
>Oak quarter sawn is .15-inch and plain sawn is .31-inch
>
>Basswood quarter sawn is .19-inch and .28-inch plain sawn. (also fairly
>stable)
>
>Butternut quarter sawn is .10-inch and plain sawn .19-inch. (lower change
>but more cupping problems.)
>
>These numbers come from a chart that Tom Liebl, who designs furniture and
>boats in Madison Wisconsin, had published in the Fine Woodworking book on
>Wood and How to Dry it (available at most good woodworking stores).
>
>
>Joe Dillett
>The Carving Shop
>645 E. LaSalle St. Suite 3
>Somonauk, IL. 60552
>(815) 498-9290 phone
>(815) 498-9249 fax
>http://www.thecarvingshop.com
>jdillett at thecarvingshop.com
>http://www.carvingmagazine.com Carving Magazine web site and Readers Forum
>**************************************************
>
>
>
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