Since most of us building furniture live in modern homes with central air and heat and (some) use polyurethane coating, is the seasonal movement of a finished piece really that much? I’ve made a number of pieces (boxes, tables, desks with drawers etc)7+ years ago without knowing much about wood movement and yet to see a crack, split or anything. It would seem to me the temperature in a modern home wouldn’t fluctuate more than 15-20 deg. over the course of a year. And humidity is well within check. I understand the reason behind the time tested methods to prevent movement (page 38-39 of Building Furniture–dovetails, also bread board ends etc) but our fore fathers didn’t have climate controlled homes or urethane coatings. (not to mention Gorilla Glue)Has anyone finished a piece and seen cracks or splits years down the road?
Edited 8/18/2007 3:43 pm ET by NKYwoodworker
Replies
NKY,
It is long-term swings in humidity, not temperature, that cause wood to move. So that, along with air-conditioning's de-humidifying effect in the summer, it is helpful to humidify, along with heating, in the winter to stabilize the environment of solid wood furniture.
The reason that period furniture makers could get away with violation of the rules about seasonal movement, is that their homes had no central heat, and no air conditioning. The relative humidity of their homes was relatively (heh) constant (but high). Cold outside air in the winter can hold only so much moisture. When air at 60% relative humidity at 20 degrees is heated to 70 degrees in our centrally heated homes, its relative humidity drops way down. It is drier than even air conditioned summer air. And so wood shrinks in this environment- even wood finished with miracle polyurethane-- even if it is glued with Orangutan, or Mighty Joe Young glue--- and if the wood is restrained from moving, cracks develop.
Incidentally, the best time-tested methods have more to do with allowing for movement, than restraining it. Things like solidly glued breadboard ends, and drawer bearers glued and nailed across solid ends are what cause cracks to show up in desk lids, case ends and table tops. Sliding dovetails, and floating panels, not so.
Then there is the effect of geographical changes. Some places have higher humidity than others, some places experience greater seasonal changes in humidity than others. If you build in one climate, (London, Seattle) and move to another (Arizona) how well your furniture holds up to the move will depend on how it was put together. I recently worked on a desk that had been built in England in the mid 1800's and shipped to equatorial South America. When its owner moved to Washington, DC, his family heirloom fell to pieces the first winter. He couldn't understand how an antique could be fine for the first 150 years of its existance, then suddenly self-destruct. Can you?
Ray
Ray,
Much appreciated. And now you mention it, the joinery is to "allow" movement. The more projects I complete (for others) the more I'm concerned about movement. Learn something new on every project... not to mention message boards. Thans again..........NKY
The 19th. century cabinet makers didn't have urethane coatings, they had something better when it comes to blocking transfer of water vapor. They had shellac, which is the superior product in that regard.
Constructing furniture to allow for seasonal movement isn't much of a hardship, anyway. And, besides who knows when conditions won't remain so ideal. Power fails--sometimes for weeks. A pipe bursts while you are on vacation. Your boss moves you from Florida to Arizona.
Edited 8/18/2007 11:56 pm ET by SteveSchoene
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