Rate of Wood Moisture Gain from Ambient Humidity

      How long will it take for furniture stored in an unconditioned warehouse to equilibrate with the ambient moisture conditions? April 18, 2010

We dry our lumber to 5.5% MC. We store our finished furniture in a warehouse in a town with an EMC of 14%. No climate control (no heat or cooling - just a roof, walls and a door). The furniture is finished with NC lacquer on all surfaces.

1) How many weeks can the furniture be stored before it is at 14% MC?
2) If the wood furniture is at 14% MC and we truck it to Las Vegas, Nevada and store it at 4% EMC, how fast does it move from 14% to 4%?

The construction allows for the movement associated with MC changes from 4% to 14% and back. However, the wood itself can crack even if unattached to anything else if it loses or gains moisture too fast. I have read all about MC and EMC and their relationship to RH and temperature. The big question is: how long?

The wood species is Nothofagus pumilio, specific gravity .49, Janka hardness of 990. Let's say the ambient temperature is 95 degrees Fahrenheit.

Forum Responses
(Sawing and Drying Forum)
From contributor C:
When the lumber is dry, do you close stack and wrap in plastic to keep the moisture out, or at least slow down the moisture gain?

From Professor Gene Wengert, forum technical advisor:
To achieve 14% EMC, you need about 73% RH average (most of the USA would be at 12% EMC - 65% RH - average in a covered but opened shed, even in the South and even in the summertime; a closed warehouse would be drier). However, dry wood will not achieve 14% MC due to the hysteresis effect and the long time required and the finishes applied. To achieve 12% would take months and months in most cases, and colder would take longer than warm. Similarly for wood going from 14% MC to 4% EMC. Having said that, any exposed, unfinished end grain will go faster (weeks) than the flat grain. Also, some drying and subsequent problems can begin to show up after a 2% MC change.

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