I've recently aquired a de-humidifier in an attempt to stop my tools and
machines going rusty during the winter - what's a good relative humidity level
to aim for so I don't make the air too dry for all the wood in the workshop?
As Leon has so perspicaciously stated, it is not so much the relative
humidity as it is the relationship of the highs to the lows, and the
swiftness with which they occur.
What will really rust your tools is a cold front, precipitously
followed by a warm front (that happens to be carrying a lot of
moisture, as is their nature.)
Unfortunately, the reverse is also true.
If you simply allow your tools to live at the ambient air temperature,
and only bring them up to working temperature in a gentle way - you
will be fine.
Wood does not react as quickly to temperature/moisture changes as cast
iron, so they will be just fine ( and prolly achieve closer to the
ideal mc ) if left alone.
"People funny. Life a funny thing." Sonny Liston
Thomas J.Watson - Cabinetmaker (ret.)
tjwatson1ATcomcastDOTnet (real email)
In my shop, er, studio, the temp ranges from 60F to 75F and the RH
from 50 to 70.
Right now, the temp is 65 with a RH of 60. At the peak of summer, the
temp might reach 75 for a short while and if I didn't run the
dehumidifier it'd reach around 90, but I keep it at about 60.
Obviously right now the dehumidifier isn't running. My furnace is a
condensing type, that does a good job of further wringing out already
Check out "Understanding Wood" by Hoadley for a discussion on
temperature, relative humidity and grains of moisture in the air.
What this means is that if the water content of the air is unchanged,
the RH will rise and fall opposite the temperature. The temp rises,
the RH falls. The temp falls the RH rises. Of course if the temp is
unchanging, if the RH rises there's more moisture in the air, if it
falls, less. But that's obvious.
Probably more than you asked for.
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