As I understand it the wood will over a period of time come to the same
moisture content as its environment.
So if your normal humidity is 14-16% the wood will absorb moisture
until it is also 14-16%.
Obviously wood in direct contact with water will absorb more so timber
in exterior jobs should be kept from direct ground contact.
On 6 Oct 2005 07:09:09 -0700, [email protected] wrote:
>how fast does wood absorb moisture? relative humidity where i am is at
>14 to 16%. My wood was dried to 8%; specie is meranti. weather is
>sometimes rainy.
>
>what factors affect wood to absorb and not to absorb moisture?
well woods are different some do it fast some are slow.
but if your humidity is so low the wood is not going to change. it
may shrink a bit at best. once wood is fully dry it does not absorb
much moisture. I don't think I see much of an increase maybe 1% over
the year or so.
Knight-Toolworks
http://www.knight-toolworks.com
affordable handmade wooden planes
<[email protected]> wrote in message
news:[email protected]...
> how fast does wood absorb moisture? relative humidity where i am is at
> 14 to 16%. My wood was dried to 8%; specie is meranti. weather is
> sometimes rainy.
>
> what factors affect wood to absorb and not to absorb moisture?
>
Wood will reach an Equilibrium Moisture Content (EMC) based on the relative
humidity (RH) of the air surrounding it. Tables for same and lots of
reliable information at
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm
Chapter three is where, though a search for "air drying" or "storage of
lumber" at http://www.fpl.fs.fed.us will also turn some good papers.
For your information, at 100% RH, the EMC is around 30% moisture by weight
for nearly all woods. It's called the Fiber Saturation Point (FSP). After
that, it's called waterlogging, and requires liquid.
"Australopithecus scobis" <[email protected]> wrote in message
news:[email protected]...
> Ground contact, though, I gotta chime in. Ground contact often means dirt
> out in the rain. I made raised garden beds out of plain old 2x. They
> rotted out at the bottom. They got alternately wet and dry, wet and dry,
> and away they went. OTOH, your typical viking craft sunk in a lake
> somewhere, or some prehistoric Australian pine tree sunk in a
> bog, will become saturated with water, but won't rot. So, yes, wood
> immersed in liquid water will come into equilibrium, become saturated. No,
> that's not why we keep wood off the ground. One situation,
> equilibrium moisture content, is sorta kinda static. The other, ground
> contact, has to do with change. Rotting could happen in either case;
> greater than 25% moisture or alternating wet/dry.
>
Oxygen is the determinant. The bacteria and fungi that do the deed are
aerobic. Bottoms of bogs (sorry, blokes, I know what a bog is to you) and
lakes are poorly oxygenated. Also often very acid and thus highly
mineralized, another thing the decay bacteria don't like.
There are a bunch of logs that sank in the big lake north of here waiting to
come to market after a hundred years. Trouble is, they make big holes when
they're lifted.
In article <[email protected]>, [email protected] wrote:
>As I understand it the wood will over a period of time come to the same
>moisture content as its environment.
You understand it incorrectly. Over time, the moisture content in wood will
reach an equilibrium with its environment; that is, the wood no longer absorbs
moisture from the environment, nor does the environment absorb moisture from
the wood. This is NOT the same as the moisture content being the same in each.
>
>So if your normal humidity is 14-16% the wood will absorb moisture
>until it is also 14-16%.
Not correct. Not even *close* to correct. If your normal humidity is 14-16%,
then you live in the Atacama Desert -- and wood will have a moisture content
close to zero. Conversely, at room temperature, wood will have a moisture
content of 14-16% at humidity of approximately 75 to 80%.
Google < "moisture content" wood equilibrium > to learn about this.
>
>Obviously wood in direct contact with water will absorb more so timber
>in exterior jobs should be kept from direct ground contact.
"Direct contact with water" and "direct ground contact" are not the same.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
<[email protected]> wrote in message
news:[email protected]...
> As I understand it the wood will over a period of time come to the same
> moisture content as its environment.
NOT.. Many places have a humidity level of 90+%. The wood in the fences,
homes do no have 90% moisture content.
> So if your normal humidity is 14-16% the wood will absorb moisture
> until it is also 14-16%.
NOT
>
> Obviously wood in direct contact with water will absorb more so timber
> in exterior jobs should be kept from direct ground contact.
Close, but what does ground contact have to do with direct contact with
water?
>
<[email protected]> wrote in message
news:[email protected]...
> how fast does wood absorb moisture? relative humidity where i am is at
> 14 to 16%. My wood was dried to 8%; specie is meranti. weather is
> sometimes rainy.
If the wood has a constant source of condensed moisture, read that as
setting into apuddle of water it will eventually become water logged.
Humidity has little effect by compairison. I live in Houston and the
humidity level is consistantly above 80%. No lumber supplier in Houston
that I know of stores their lumber in a low humidity environment. Over time
the humidity level will cause some dimentional changes however the moisture
content of the wood is not going to go back up to 80% here in Houston if
kept out of the rain.
As an example, when using new cedar pickets they are often still wet when I
nail them up on a fence. A week to 10 days later the pickets shrink and dry
out in this humid environment.
> what factors affect wood to absorb and not to absorb moisture?
>
> thanks,
>
> NORY
>
On Thu, 06 Oct 2005 17:45:40 +0000, Doug Miller wrote:
> "Direct contact with water" and "direct ground contact" are not the same.
I found the comments about equilibrium enlightening; thanks to the posters
who described the situation so clearly.
Ground contact, though, I gotta chime in. Ground contact often means dirt
out in the rain. I made raised garden beds out of plain old 2x. They
rotted out at the bottom. They got alternately wet and dry, wet and dry,
and away they went. OTOH, your typical viking craft sunk in a lake
somewhere, or some prehistoric Australian pine tree sunk in a
bog, will become saturated with water, but won't rot. So, yes, wood
immersed in liquid water will come into equilibrium, become saturated. No,
that's not why we keep wood off the ground. One situation,
equilibrium moisture content, is sorta kinda static. The other, ground
contact, has to do with change. Rotting could happen in either case;
greater than 25% moisture or alternating wet/dry.
And I don't know any of this stuff myself; I just got "Encyclopedia of
Furniture Making" from interlibrary loan.
--
"Keep your ass behind you"
vladimir a t mad {dot} scientist {dot} com