Indoor Conditions for Museums with Wood Furniture

Maintaining constant, correct humidity is the paramount concern. February 15, 2009

A local museum has asked for my opinion on the temperature and humidity level in the building during the off season (winter) when they are closed. They need to cut the budget and lower expenses. The main content of the museum is large, solid hardwood clocks handmade in the early 1900's by local craftsman. One of which Henry Ford himself offered $1,000,000 for. These craftsman were farmers at the time and carved in the winter months to pass time. They were simple good people and turned the money down to keep the collection together. They donated the clocks to the city.

Forum Responses
(Furniture Making Forum)
From contributor Y:
Im not sure enough to answer your question directly, but a suggestion may be that they could move the items into a smaller room that they could keep more better environmental controls on, instead of having to keep the entire building heated.

From contributor D:
Check with one of the U.S. decorative arts restoration/museum studies programs. I believe that the U of NY at Syracuse and U of Pennsylvania at Philadelphia both have programs.

From the original questioner:
Moving the clocks is not an option. They are huge, up to 9' tall and 5' wide.

From contributor G:
Is this the Spillville collection done by the Billy brothers? If I remember it correctly, out in Iowa?

From the original questioner:
Yes it is. Have you seem them? They are amazing. I had to pleasure of doing some minor repair on the clocks a few years back. I had to glue small pieces back on that were broke off during dusting. In doing so I was able to really see the clocks up close.

From contributor J:
Humidity is more critical than temperature. The Smithsonian recommends 50% and that should be maintained all year. Temp could be lowered to perhaps 50 degrees, but should be done slowly over a period of weeks.

From contributor G:
It just goes to show you what two brothers can get done snowed in during a northern Iowa winter. Yes, I saw the collection and it was wonderful. I have a soft spot for small town museums and this one is the best I have seen, although I fear it was probably 35 years ago. You might let them know that their web site doesn't display correctly, and about half the links are broken.

Contributor J is certainly correct. Temperature stability is good, but humidity changes are much more damaging. The worst is winter heating, which if no additional moisture is added, can leave indoor humidity close to zero. Alternating with summer days which can approach 100 % and you get a lot of movement, which means dehumidifiers, or air conditioning in summer. My remembrance was that that was a big building, a bit drafty and minimally insulated, if at all (basically plaster on several layers of brick). Heating and cooling must be a real cost concern, so perhaps they would be best to devote what they can on humidity control.

I envy you your ability to work with the clocks. By the way are any measured drawings available for the clocks? Is there a good color picture book of the collection?

From the original questioner:
I informed them humidity control was very important and lowering the temp should be done slowly with continued humidity monitoring. Heating costs are, of course becoming very expensive for the museum and money is very tight. With higher gas prices they are concerned tourism will continue to drop off. With that, income also suffers but expenses march on. I did not know what the minimum safe temperature should be.

The museum staff is also checking other sources to make sure the info is correct. Thank you and I am still open for suggestions. There is another very interesting book available from the museum. It is basically the Bily brothers' mother's diary. It tells what the brothers were working on and about their life. It also tells how they were scared for their lives during Orson Wells' "War of the Worlds". Life was simpler then.

From contributor P:
At the Getty museum where I work, the gallery HVAC is set to 50% humidity, and 75 degrees. All the storerooms and workshops run at the same settings. As others have written, the humidity is the most important. Remember that as temperature drops, humidity will often increase, unless acted upon by a de-humidifier.

From contributor W:
Suggest that they get a copy of "Exhibit Conservation Guidelines". It's a CD-ROM put out by the National Parks Service's Harper's Ferry Conservation Center. It's the resource for exhibits conservation and deals with storage as well.

From Gene Wengert, forum technical advisor:
I will repeat the previous posting. From a wood standpoint, only the RH is critical. Temperature does not affect wood except that water moves more slowly; however, changes in temperature can affect the RH, so monitor the RH at all times. If you were to raise the temperature quickly and yet have 50% RH, the wood would still be cool and at the surface, the RH would be much lower. So, change the temperature at a rate not to exceed 2 degrees F per hour (to be conservative).

The air must be moved or circulated to maintain the desired RH throughout. Be careful near cold walls or floors, etc.