Ideal Humidity and Temprature for Collection?

derek · 8th July 2005, 09:39 PM

I was hoping some of the museum-affiliated members could comment on ideal temprature and humidity for weapons on display. My house stays kind of dry, around 40% humidity, and I was wondering if there were any issues I should be aware of. I know that dryness is hard on ivory and eventually leather. What are the pros and cons, general rules, etc?

thanks in advance.

-d

Ian · 8th July 2005, 10:49 PM

That sounds too dry for most woods also, especially the tropical varieties which split very readily in low humidity. A museum colleague said that climate control is somewhat controversial for preserving many items of art. He recommended 70 degrees F and 70 percent humidity, but quickly added that he has no direct experience of edged weapons.

Ian.

Rich · 8th July 2005, 11:17 PM

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

Ian · 9th July 2005, 12:52 AM

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.

Quote:

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

Marc · 9th July 2005, 08:28 PM

The problem is with the different materials that compose the weapons. Can’t talk about wood, as I don’t know enough about it. Ian’s numbers, for the material he describes, make sense to me, for what is worth. However, this level of humidity is far too high for metals. In fact, anything higher than 50% RH is definitely risky for things like bronze, brass and steel. And I'm stretching it. I would feel more comfortable recommending indeed 30-40%, but this would be too dry for many woods and organics (leather, textiles...). I think 40-50% is a good compromise. If this can't be reached or it's still too dry for some materials, remember that physical barriers help a lot in isolating the metal from the environment. Thin mineral oil, nitrocellulose lacquer or, even better, microcrystalline wax may work wonders with your blades and fittings.
Another thing: dust is bad. It increases the chance of the humidity actually condensing in the surface of the metal, so if you can't encase the weapons at least keep them as dust-free as possible.

derek · 10th July 2005, 12:39 AM

Excellent info guys, thanks.

I recently had an AC breakdown and the humidity shot up from 40% to about 65% in a very short time. All is working now and it's back down to 40%, but it got me thinking.

I'll keep reading, but based on what I'm hearing - and seeing with my own stuff - it's probably a good idea to keep an eye on the leather and wood, horn and ivory. Mineral oil is one of the best tools in my preservation arsenal, I use it on metal, horn and ivory. It's cheap too. I don't think it will harm wood or leather (after all, isn't japanese clove oil mostly mineral oil w/ a hint of clove for scent?), but is there something better to fight the dry air?

BTW, I had an apartment in the UAE that had humidity levels at 80% at one point and I can tell you that NOTHING was comfortable with that. Our clothes got a faint hint of mildew and the leather on my sword scabbards got moldy

. On the other hand, 40% does in fact get pretty dry in the winter and it affects our skin. I'm sure it dries leather and wood as well. My blades like it, though.

8th July 2005, 09:39 PM	#1
derek Member Join Date: Dec 2004 Posts: 215	Ideal Humidity and Temprature for Collection? I was hoping some of the museum-affiliated members could comment on ideal temprature and humidity for weapons on display. My house stays kind of dry, around 40% humidity, and I was wondering if there were any issues I should be aware of. I know that dryness is hard on ivory and eventually leather. What are the pros and cons, general rules, etc? thanks in advance. -d

8th July 2005, 10:49 PM	#2
Ian Vikingsword Staff Join Date: Dec 2004 Location: The Aussie Bush Posts: 4,207	That sounds too dry for most woods also, especially the tropical varieties which split very readily in low humidity. A museum colleague said that climate control is somewhat controversial for preserving many items of art. He recommended 70 degrees F and 70 percent humidity, but quickly added that he has no direct experience of edged weapons. Ian.

8th July 2005, 11:17 PM	#3
Rich Member Join Date: Dec 2004 Location: comfortably at home, USA Posts: 432	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

9th July 2005, 08:28 PM	#5
Marc Member Join Date: Dec 2004 Location: Madrid / Barcelona Posts: 256	The problem is with the different materials that compose the weapons. Can’t talk about wood, as I don’t know enough about it. Ian’s numbers, for the material he describes, make sense to me, for what is worth. However, this level of humidity is far too high for metals. In fact, anything higher than 50% RH is definitely risky for things like bronze, brass and steel. And I'm stretching it. I would feel more comfortable recommending indeed 30-40%, but this would be too dry for many woods and organics (leather, textiles...). I think 40-50% is a good compromise. If this can't be reached or it's still too dry for some materials, remember that physical barriers help a lot in isolating the metal from the environment. Thin mineral oil, nitrocellulose lacquer or, even better, microcrystalline wax may work wonders with your blades and fittings. Another thing: dust is bad. It increases the chance of the humidity actually condensing in the surface of the metal, so if you can't encase the weapons at least keep them as dust-free as possible.

10th July 2005, 12:39 AM	#6
derek Member Join Date: Dec 2004 Posts: 215	Excellent info guys, thanks. I recently had an AC breakdown and the humidity shot up from 40% to about 65% in a very short time. All is working now and it's back down to 40%, but it got me thinking. I'll keep reading, but based on what I'm hearing - and seeing with my own stuff - it's probably a good idea to keep an eye on the leather and wood, horn and ivory. Mineral oil is one of the best tools in my preservation arsenal, I use it on metal, horn and ivory. It's cheap too. I don't think it will harm wood or leather (after all, isn't japanese clove oil mostly mineral oil w/ a hint of clove for scent?), but is there something better to fight the dry air? BTW, I had an apartment in the UAE that had humidity levels at 80% at one point and I can tell you that NOTHING was comfortable with that. Our clothes got a faint hint of mildew and the leather on my sword scabbards got moldy . On the other hand, 40% does in fact get pretty dry in the winter and it affects our skin. I'm sure it dries leather and wood as well. My blades like it, though.