Peter,
After you told me to post a question on PMQ Think Tank about dough/proofer pans, I did get an answer from Tom Lehmann as you told me. Then you had shown me your experiments and I was still wondering about expansion inside the plastic bags, so I posted a question about expansion on the same thread. Here is what Tom Lehmann told me. Maybe other member of this forum would be interested in reading the two answers Tom had replied to about using plastic bags for proofing. I got the bags and will try some of my dough this coming week proofing in the bags to see if there is a difference.
These are the two answers I received.
Norma;
Not to worry. Because the bag doesn't create an insulating layer, there is no need to leave the bag open to help cool the dough ball(s) down. It won't sweat either because the bag will be in direct contact with the dough, and sweating only takes place when there is an air space around the dough ball such as is the case when cans or boxes are used. Pretty nifty, eh?
Tom Lehmann/The Dough Doctor
Norma;
Ahhh, that is why it is important to twist the bag closed and tuck the pony tail under the bag. This allows for some additional expansion of the bag, in addition to the normal stretching as the dough ball expands in size. If you were to close the bag with a knot, the bag would have a high probability of rupturing as the gas pressure increased, the twist and tuck method of closure allows for some escape of gas, plus a little additional expansion. In all my years, using this method, I've never had a bag burst.
Tom Lehmann/The Dough Doctor
Norma