Hi Rich:
Actually a relative humidity of 70% at 70 F is quite comfortable for most people. It does not lead to a lot of moisture problems. Remember that we are talking about
relative humidity, and that lower temperatures sustain less total water content than higher temperatures.
The guidelines published by the American Society for Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) recommend that indoor climates be maintained at temperatures between 73-78 deg F and a relative humidity of 30-60% in summer and 68-74 deg F with 30-60% relative humidity in winter. A substantial fraction of people find 30-40% RH to be very drying for the skin and mucous membranes of the eyes and throat, and quite irritating. Above 60% RH there is an increasing likelihood of mold problems in cooler areas of the house (basement, laundry, bathroom).
My colleague who recommended 70 deg F and 70% RH was responding to my concerns about certain tropical woods that had split on hilts from the Philippines and Indonesia. This was happening at stable RH levels of about 40%. He pointed out that these woods typically come from tropical climates that remain close to 100% RH and temperatures seldom fall below 75 deg F. That was why he suggested the 70% RH for storage -- not too high to cause mold problems in a well ventilated space, but high enough to prevent excessive drying out of the woods.
Derek, you've probably heard both ends of the spectrum here. Choosing somewhere in between may be a good compromise. Certainly the mid-point of the ASHRAE guidelines might be a starting point, and see where you go from there.
Ian.
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Originally Posted by Rich
I've been collecting and studying antique knives and
swords of all types for about 50+ years. I keep mine
in the 68-78 F and 30-40% humidity year round. Never
had any trouble with rust or leather rot, wood splits,
etc. It's more drastic changes in temp and humidity
that cause problems. IMHO 70% humidity is "dripping"
wet - way, way too humid.
Rich S
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