No that's just wet, 100% humidity just means a sample of air cannot hold any more water vapour, a hot body of wood can still dry in 100% humidity air if the water is boiled off.
AJH
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17 years ago
Cupped Floorboards
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17 years ago
No, that's 100% *relative* humidity.
a hot body of wood can still dry in 100%
Only by raising the air temprature so the local relative humidity is LESS than 100%.
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17 years ago
Yes, I should have specified RH but the fact it's given as a percentage rather than grammes/m3 or grammes/kg implies that it's relative rather than absolute.
As long at the temperature is above the local boiling point then water will leave it as vapour. This will occur at all humidity ratios of the surrounding atmosphere. AJH
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17 years ago
The fact that the temperature is above the dew point means that the RH IS LESS THAN 100%!!!
Boiling point has nowt to do with it.
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17 years ago
I cannot see the point you are trying to make.
I see drying wood as a two stage process, one to empty the cell contents to the stage it won't support microbes which will rot it and two to get it so it's reasonably dimensionally stable for the environment it will be used in.
Original replies to the original poster had adequately covered the interesting difficulties in accommodating relative changes in dimension across axial, radial and tangential faces, which lead to cupping, among other things, if a house dries out.
Stuart posted that wood could still dry in a 100% humidity atmosphere, I replied that it would only do so if boiled off. I think boiling is defined as the temperature at which the vapour pressure of a liquid exceeds atmospheric pressure.
You picked up on the point that this referred to relative humidity, rather than absolute. 100% absolute humidity would be a steam atmosphere. In both cases water would only leave the wood as vapour if its temperature went above the local boiling point, e.g. it could happen in below atmospheric pressure conditions.
I cannot see what dew point has to do with this. If other posters wish to give some input I'm happy to discuss but let's not extend this if it's just going to be a standard bipartisan argument.
AJH