Date: Fri, 21 Oct 2005 00:38:16 -0400
To: WSFA members <WSFAlist at WSFA.org>, WSFA members <WSFAlist at WSFA.org>
From: "Mike B." <omni at omniphile.com>
Subject: [WSFA] Re: Book shelves and cases
Reply-To: WSFA members <WSFAlist at WSFA.org>

At 12:03 AM 10/21/2005 -0400, dicconf wrote:
>
>Just be sure that the wood is kept in the same temperature and moisture
>conditions as the room it will be in.  Terry Pratchett learned what
>happens when a bookcase with shelves in routed slots, carefully built
>in a cold garage, is brought into a warm room.  Around 3 A.M. the
>fully-loaded shelves finished shrinking a little bit more than was
>allowed for.

I noted that one of the "how-to" articles pointed out here lately suggests
bringing the wood home and whacking it together as quickly as possible so
it doesn't warp first.  For using cheap shelving material to build simple
bookcases where aesthetics and long life are not factors this might work
well enough, but the wood is going to change anyway, and only the nails or
screws are going to be stopping it.  This will result in stresses within
the bookcase.  Over time this might result in the fasteners pulling out,
the wood cracking, or the whole thing going out of square.

This is more a problem with today's wood than it was 60 or more years ago.
Modern wood is grown rapidly on tree farms much of the time, and the grain
is much wider than the wood from trees that grew in natural forests over a
longer period of time in the past.  Wider grain tends to result in more
movement with water content changes.  The stuff you find at the home center
is mostly kiln dried, which means the moisture content is likely to be
under 15%.  If your house is pretty close to the same, the wood will
probably be stable enough.  If your house is drier or wetter, the wood will
change over time.  Paint and varnish (particularly the new plastic
varnishes) will limit this a lot.

Recommended practice when building fine furniture, or other things that use
nice wood and fancy craftsmanship, is to put the wood in the place where
the item will be used, and leave it there for a couple of weeks or longer.
This lets the wood "acclimate" to the environment.  Yes, it may warp,
twist, cup or even split, but better it do that in board form than after
it's been made into something nice.  In board form you can do things to fix
the problems before you cut out the parts (planing, careful layout of
parts, etc.).

Note that wood shrinks and expands across the grain a lot, and along the
length of the grain very little or not at all.  Proper design will take
this into account (one reason you don't fasten a table top solidly to the
apron...).

If anyone wants to talk about this more sometime, I'm happy to do so.  I'm
not a professional, but woodworking has been a hobby for a while now.

-- Mike B.
--
Maybe if we made a giant badger....