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Wednesday, April 20, 2016

Brooklyn Museum
Brooklyn Museum wrote:
Egyptian works currently on display in our Egyptian galleries...

Egyptian works currently on display in our Egyptian galleries date from ca. 3500 B.C.E. through 395 C.E. and are composed of various materials including papyrus, wood, ivory, stone, metal, and terracotta. Many of these materials are reactive to their environment however; the climate in some of our Egyptian galleries is not yet controlled. Depending on outdoor weather conditions, the temperature and relative humidity in the galleries may reach levels that are not necessarily ideal for certain collection materials.

Relative humidity is a measure of the amount of moisture in the air relative to the amount the air is capable of holding, expressed as a percentage. Low relative humidity levels can cause desiccation, shrinkage, and cracking of organic objects including papyrus, wood, and ivory. High relative humidity can cause swelling of organic materials, induce corrosion on metal objects, and promote microbial growth. Dramatic fluctuations in relative humidity can cause rapid dimensional changes in organic materials, which can be particularly detrimental. To ensure the safety of objects exhibited in non-climate controlled areas of the museum, the Conservation Department works closely with the Design Department to design cases that function as micro-environments.

In general, a consistent relative humidity between 45% and 55% is preferred for most works. Some metal objects require levels of 40% or lower to prevent corrosion. To create an ideal environment, we typically employ silica gel, a chemically inert, porous, and hygroscopic material capable of absorbing moisture in humid environments or releasing moisture in dry environments. We can condition silica gel to the desired moisture level by drying it in an oven or humidifying it in a closed, damp environment. We then place the preconditioned silica gel in compartments within a sealed display case where it will maintain the desired humidity for about one year. We regularly monitor relative humidity within these micro-climates using hygrometers; you may have noticed these small devices in some of our exhibition cases.

Be sure to visit our Egyptian galleries during your next visit to the museum!

Posted by Elyse Driscoll 

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