Freezing History

Today's post comes from guest blogger Lauren Jaeger, who joined the staff of the Bureau of Historic Sites and Museums in 2014 as part of the PHMC's Collections Advancement Project. Lauren and her colleague Rachel Yerger have been working on various site inventory projects, collections research, and object care and preparation for the Pennsylvania Lumber Museum's new core exhibits, set to open later this year. Thanks, Lauren, for the text and photos.

“It’s time to take the clothing out of the freezer.” Not something you hear every day, right? But lately two of our curators have been talking about freezing all kinds of objects.

It all started with some bugs - carpet beetles, to be exact. We found evidence of these pests in the textile collections at the Pennsylvania Lumber Museum. Carpet beetles feed on wool, fur, silk, and a variety of other materials found in museums. Not wanting to introduce these insects to our recently renovated Visitors Center, we decided to freeze the objects.

You are probably wondering why curators would put important museum objects in a place meant to hold ice cream. Well, freezers also happen to be the preferred location for stopping infestations. Cooling an object to minus 20°C for one week typically kills most insects without freezing or causing damage to the actual object. However, please don’t try this at home before doing your own research. Certain objects, such as paintings, can be seriously harmed when cooled. We consulted with a conservator to confirm that our objects could withstand the cold. And don’t worry. We would never put our objects in a freezer with other food items. Several PHMC sites have special freezers exclusively for objects and have been practicing this recognized approach to infestations for years.

As you might expect, we have quite a few Woolrich jackets in our collections at the Lumber Museum. We froze this one along with over 140 other objects ranging from patches to long underwear. (Mom, if you are reading this, I’d really like a buffalo plaid shirt for my birthday).

Packing the objects for their arctic adventure took several days. We bundled them up in clear polyethylene bags, removed as much air as possible from the bags, and then sealed the bags with tape. Following the advice of the conservator, we gave extra attention to certain objects to ensure protection from the cold temperatures. For example, we covered fragile coat buttons with acid free tissue to provide additional support and prevent condensation. Once bagged, the items were placed in a giant freezer at Landis Valley Village and Farm Museum. Then we waited.

Objects defrosting on the drive back to Harrisburg from Landis Valley’s freezer.

A few weeks later, we returned to Landis Valley to retrieve our cool objects (literally cool…we had to wear gloves to protect our hands from frostbite). After allowing the bagged objects to warm to room temperature, it was cleaning time. Now, most people wash their dirty clothes. Museum people do it a bit differently: meticulously vacuuming clothing and other textiles through a nylon screen to gently remove dust, insect remains, and other small particles.

I imagine that the original owner of this Pennsylvania State Forestry Officer’s jacket would be quite amused to see us vacuuming his uniform.

As we finish vacuuming each object, we carefully pack it for the return trip to the Lumber Museum where it will find a bug-free home in the new core exhibit or climate-controlled collections storage room.

For more information about freezing objects, check out this Conserve O Gram from the National Park Service and this article from the Canadian Conservation Institute.