Museum Monday: Hygrothermographs for the Layman

What is that box with all the dials sitting in the corner of the gallery?

A hygrothermograph. Photo: Oakton.

Chances are, it’s a hygrothermograph. It’s a device that tracks temperature and relative humidity over time. Museum staff use it to understand the environment in a space, and how it is affecting the objects being displayed. So, you ask, why does this matter?

Many objects are sensitive to changes in relative humidity. Think of doors that stick in their jambs in the summer. Drawers that fit tighter when it’s humid out. Think about your hair. And that’s how hygrothermographs work. A lock of hair is attached to gauges within the device. When there is more humidity in the air, the hair becomes longer, and this relays to the pens tracking the relative humidity on the graph.

Let’s throw another word into the mix: hygroscopic. This term is applied to materials that absorb and hold water, usually resulting in some sort of physical change. Wood, ivory, textiles, and paper are examples of hygroscopic materials. Stone, ceramic, and metal are not (though I will point out that damp environments are not good for storage of metals, as this can accelerate corrosion).

Hobo datalogger. Photo: Onset.

So using hygrothermographs to determine conditions in a space, and how museum staff will display and store objects based on whether they are hygroscopic or not is a big part of preventive conservation practice. Many museums are shifting now toward the use of dataloggers to track relative humidity and temperature, so that digital graphs that may be more easily analyzed. Still, a lot of conservators like hygrothermographs for their instant visual information and ease of calibration.

About Becky Fifield

Becky Fifield is a cultural heritage professional with 25 years experience in institutions large and small. She is currently Head of Collection Management for the Special Collections of the New York Public Library. An advocate for preventive conservation, Ms. Fifield is a Professional Associate of the American Institute for Conservation, Chair of the AIC Collection Care Network, and former Chair of Alliance for Response NYC. She is also a scholar of 18th century female unfree labor and dress. There's a bit of pun in the title The Still Room, delineating a quiet space brimming with the ingredients of memory, where consideration, analysis, and wordcraft can take place. Ms. Fifield’s interests include museum practice, dress history, historic preservation, transit, social and women’s history, food, current events, geneaology, roadtrips, and considerations on general sense of place. Becky and her husband, Dr. V, live in the Hudson Valley.