Just picked up enough red oak to make a couple small tables. I have
5/4 & 6/4 planks (the 6/4 is quartersawn for the table top), and a
chunk of 12/4 for the legs. This wood came from a local hardwood
supplier that stores their wood stacked but unstickered in a metal
shed (unheated, it seems). My garage is at 43% RH tonight. When I
put my hygrometer inbetween the now stickered boards, it reads 50% RH.
Question: is it safe to assume that I can use this wood when the RH
right up snug against the wood is the same as the garage? I'll
probably do the weigh and bake moisture test tomorrow, but I am
curious about the RH idea ....
On 23 Jan 2004 20:05:08 -0800, email@example.com (Scott) wrote:
When it is safe to use the wood involves a reciprocity between the
moisture content of the wood and the stability of the environment that
it will live in.
The moisture content of the wood is best measured by a meter that is
designed for such use and it is generally agreed that the moisture
content should be about 6%.
The reason that it is called out at 6% is that this is the moisture
content that will best survive in a controlled environment that is
about 68 to 72 degrees and has a relative humidity of about fifty
There are places in both England and the US that might not have
central heating or summer air conditioning and this would make the 6%
measurement almost worthless.
The real game is about the equilibrium moisture content for the piece
in relationship to the environment that it will live in.
If you make a piece with stuff that's living at the 6% level and put
it in a home in Florida that does not use air conditioning, that would
be a bad thing.
Find out what the general conditions of the space is that the piece
will live in and then build your piece with stock that is tempered
Thomas J. Watson-Cabinetmaker (ret)
Real Email is: tjwatson1ATcomcastDOTnet
What Tom means to say is consult the tables, where 50% RH equates to an EMC
of 8-9%, which is the standard to which wood is kilned where I live and
where I've been.
Once the wood leaves the storage area (we used 45%RH at school) it adjusts
to the ambient conditions. Knowing this, a woodworker allows for movement
in his projects. That's why panels are framed and floated, and tabletops
merely held down, not fixed. Finishes slow the effects of rapid RH change
by slowing uptake and release of moisture in the wood, which is why we apply
finishes to both sides.
Build tight in high humidity, loose in low, but smart in all. Look to your
design, and try a book like Hoadley's _Understanding Wood_ for the proper
Neat stuff here, too
Funny how many guys will buy a classical guitar made insome coastal
village in Spain, and have it shipped to the desert West . . . and
watch that expensive Brazilian Rosewood form nice cracks . . .
The mean annual RH in my home one year was 42 percent; this is now the
RH I maintain when I glue a guitar together. The wood I use for
guitars has been stored locally for years, and is thus ready to work
with. The oak I picked up yesterday ... I don't know it's history. I
think I'll call the supplier today, and learn more about their stash,
and perhaps see if they can give me a moisture content reading (since
I lack a meter of myown at this time). Also, I see Hoadley has a nice
map showing ideal moisture contents for the USA; for Idaho it looks
like your 6% figure is right on.
Called the hardwood retailer to ask about MC: he said they bring the
wood into the shop at 6-8% MC, where it sits and equilibrates to the
local climate until someone buys it. Since I live in the local
environment, he said that I should feel free to begin building.
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