You wrote: Message: 17 Date: Tue, 7 May 2019 13:27:44 +0100 From: Helen Smith <[email protected]> Subject: [Consdistlist] Experience with climate controlled showcases for temperature as well as relative humidity:
I am working with a client who wishes to display original, historic photographs in a room which experiences high and fluctuating temperatures and uncontrolled humidity throughout the year. Installation of HVAC (Heating Ventilation and Air Control, ie air conditioning) to the room is not possible. Does anyone have any experience commissioning and/or using showcases built with active temperature controls? We?re looking to hold a stable temperature in the 16-18*C range and 40-50 % RH, while the room can easily reach above 30*C on hot days. Many thanks Helen Smith ACR, Preventive Conservator, UK We have a humidity and oxygen controlled display case for an Egyptian mummy in our galleries. The size of the plinth hides all the machinery inside it. Most of this is due to oxygen control in it, which is not relevant to you. We had the case locally designed by a local engineering firm. If you are not wanting a large plinth with your photograph, then you would require ducting of some form to take the air in the frame out to where it would get air conditioned and humidity adjusted, then pumped back in. This can be through an ordinary air conditioner, humidifier, de-humidifier or full HVAC in another area (so long as the run of ducting is not too long), possiblyy with silica gel in the frame for final rH adjustment. If the volume of the frame is small, the volume of it will be rapidly heated in the room, so a relatively high air exchange would be required. A tight seal may not be required in this circumstance, just a positive pressure of the desired rH and T of air. You might even be able to dispense with “air out” ducting, just pump in conditioned air at positive pressure and let it leak out of the case, provided the leak rate is high enough to maintain the temperature. Our mummy case obviously has a very tight seal to maintain the zero oxygen environment, but still works on a positive pressure principle. If there is a leak, it is conditioned air leaking out, not unconditioned air leaking in. This all ends up being relatively expensive, and you almost might as well install the air conditioner for the whole room. You don’t need to strictly control the room to +/-2˚C, just make sure the T doesn’t exceed 25 ˚C, drop below freezing, or change rapidly (more than 5˚C/day). Humidity alone is relatively easily controlled with silica gel inside the frame. Pumping a coolant through the frame would have the risk of a leak. You could also run into problems with condensation on the outside of the frame/case. Having a cooled glass surface exposed to a hot, humid room could result in humidity condensing on the glass. What are the light levels like? Those are my thoughts, although I have never personally constructed a microclimate display case. Hope that helps. Val Valerie Tomlinson | Conservator | Auckland War Memorial Museum | Tāmaki Paenga Hira | The Domain, Private Bag 92018, Victoria Street West, Auckland 1142, New Zealand | M | P +64 9 306 7070 ext7304 | E [email protected] [https://www.aucklandmuseum.com/]<https://www.aucklandmuseum.com/service-pages/signature-am> Auckland Museum Trust Board ("Auckland Museum") accepts no liability for any opinion contained in this email. The material in this email is confidential to the recipient named above. If you are not the intended recipient: please do not copy, use or disclose this communication; please notify us immediately by email or by telephone (64 9 309 0443) and then delete this email. Where this is a communication unrelated to the business of Auckland Museum, Auckland Museum does not accept any responsibility for its contents. ##################################################################################### This e-mail message has been scanned for Viruses and Content and cleared by MailMarshal ##################################################################################### ****** Unsubscribe by sending a message to [email protected] Searchable archives: http://cool.conservation-us.org/byform/mailing-lists/cdl/
