What exactly does the phrase “stewing in its own juices” mean in relation to document preservation? That’s exactly what associate research professor Patricia McGuiggan and her colleagues set out to establish in their recently published paper “Stewing in Its Own Juices? The Permeability of PET by Water and Acetic Acid”. Through a series of experiments, the research team came to the conclusion that acetic acid didn’t diffuse through the polyethylene-terephthalate (PET) envelope, or diffused at a much slower rate due to the size of the acetic acid molecule than the water molecule. However, they acknowledge that further studies need to be conducted in order to truly actualize the permeability of specific gases with polymer films.

Figure 3: Mass loss through a PET film using a permeability cup (inset) with water as the liquid. The slope of the line divided by the area of the exposed film (25 cm2) gives the mass flux JM (eq. 2) of water vapor through the PET. The solid circles are the experimental measurements and the line is a linear regression fit to the data