This time of year I’ve been been seeing daily fluctuations in humidity in our reading room, usually in the mid 20s during the day and up to mid 30s at night. The lowest during the day has been 21%.
I’m wondering if this daily fluctuation is safe for objects hanging in the reading room, mostly wood framed paintings. The temperature reaches low to mid 70s during the day and mid 60s at night if that helps.
It would be helpful to know what city/state you are located in, but the general answer is that RH in the 20%s is not ideal. Most assuredly the RH will fall much more when you reach the lower temperatures in the winter. I would imagine it even could fall into the single digits if you are in the northern tier and probably into the teens if you are in the middle tier. The colder the outside air, the lower it will fall.
You have not said if the paintings are on canvass or on wooden panels, but it really does not matter that much. Both will not do so well at lower RH levels, but the ones on canvas will respond to changes of RH much faster, with some potential for more damage.
The imperfect solution is to keep the temperatures during the day lower. That would cause the RH to rise. You can see this already when you lower the nighttime temperature. Just have people wear sweaters. Again, dependent upon where you are located, this may not be good enough in the colder weather, so you will have to decide if the elevated risk of damage to the paintings is worth displaying them in the room. The more perfect solution probably is too expensive and may risk damage to your building, so imperfect or another location with better conditions probably are your best alternatives.
Thanks Marc. I’m in Wilmington, Delaware, so I assume the RH would fall at least into the teens, and most of the paintings are oil on canvas. I appreciate the range of options you provided – because it is a relatively older building (1930), either lowering the temperature or removing the painting are probably the best options.
Thank you for contacting C2C with your RH question. It would be optimal if the humidity in your reading room did not differ 10 percent between day and night. That said, it is also not uncommon; especially in older buildings. Whether or not you are able to control this depends on your resources and your team. Is there someone there who is responsible for controlling your HVAC system? Are you able to ask for some response on their part in managing your RH? Hopefully, you have some recourse when you are able to document that there is a problem. If not, do you have support from your administration in requesting a work order?
Thanks Tammy. The building was constructed in 1930, and we do have a pretty reliable HVAC system for that part of the building, so bringing down the temp a bit should be possible. Hopefully it won’t take too much convincing as far as human comfort goes.
ALso check out our last webinar: Storage Environments: The Big Picture, https://www.connectingtocollections.org/storage-environments/
That should be helpful.
Thanks Susan, I’ll be sure check that out!
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