Re: "Condensation" in plastic

["Mary W. Ballard" <BallardM@xxxxxxxxxxxx>]

The issue of condensation in plastic involves the moisture transition rates through the particular plastic--the ability of some plastics to stop water molecules from getting in or out; the difference between "absolute humidity" and "relative humidity;" and most especially the big difference between the rates for the adsorption of moisture by textiles and for the desorption. There is also the difficulty that many plastics have phthalate plasticizers and other volatile additives, so that most commercial plastic bags are not suitable for longterm storage of food or textiles. Moisture barriers have become quite an issue in North America where there are several types of climates; the protocols for building homes in Canada are not suitable for Florida--and vice versa--with regard to moisture barriers. Bread in a plastic bag warming in the sun is not, however, an analogy that seems probable to the chemists and mechanical engineers here working on relative humidity and temperature iss!
ues in museums. At higher temperature (inside the bag) there would be less likelihood of condensation, rather than more, unless the bread itself was at a much higher temperature initially--when bagged--and contained excess moisture, which condensated on the bag as the bread cooled. So it would be a phenomenon of cooling not heating, even on a warm day? You might talk to a home economics/nutritionist. Best wishes, Mary