The Weather Challenge

We love showing off our original materials, and several original maps are on display in Mapping Indiana: Five Centuries of Treasures from the Indiana Historical Society until April 2. But it is, of course, important to carefully care for these original works. Our conservation staff uses methods to provide the conditions necessary for fragile paper and media like those in the Mapping Indiana exhibit. One such condition is the need for original documents to be kept at certain relative humidity – or RH – levels.

The temperature in the Rosemary McKee Lanham Gallery on our fourth floor can be unpredictable in the winter months because of the open space to Eli Lilly Hall below. The large round openings, which we lovingly call “the occuli,” act as chimneys and bring additional heat to the area and lower humidity.

	1. Artsorb is a moisture-sensitive material that incorporates silica gel to help keep a sealed area at the same humidity level. For this exhibit, we cut Artsorb sheets to the same size of the mount boar used inside the frame package and sprayed them with distilled water.
	2. We placed the sheets inside a humidification chamber.
	3. We used a data logger to measure the RH inside the chamber and checked the levels every 10 minutes to reach 60 percent.
	4. To prepare a frame package, we assembled all the parts – the frame, the mount board with the original and attached window mat, and the backing board.
	5. We positioned the conditioned Artsorb beneath the mount board. Barriers beneath the original and the glazing in front maintain the humidity inside the sealed package.
	6. We monitor the RH levels with humidity indicator strips which are in the sealed package. A window was cut into the backing board to allow us to easily monitor the conditions.

While on display, we check the RH levels inside the packages weekly. If – over the course of the winter – we see the humidity lowering, we can make adjustments to provide a stable environment for originals so you can continue to enjoy them.

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