>>, try the clear oven, baking bags. They are very strong and also food grade. <<<br><br>Thanks- I’ve read this suggestion a couple of different places, but yesterday I finally got around to purchasing some. I opted for the smaller (not turkey size) "Reynolds Oven Bags", 5 to a box.<br><br>I need to experiment some more, but preliminary results look very good. I’ve folded and re-folded one of these bags tightly several times, and there’s no sign of fatigue failure at the corners of creases. The stuff does seem to be very strong for it’s weight, MUCH more so than polyethelene, and the size (10” x 16” with the opening on a 10” edge) is about ideal. It seems this would likely be both more durable and much easier to fill and reuse than a condom or balloon, and it folds very flat and thin, or, when folded and then rolled tightly, is not really much larger than a condom. You do have to take care not to trap air in it. <br><br>If my water-holding and resealing tests go well, I think this is the solution I’ve been looking for even for the smallest “Altoids tin” kits.<br><br>I think one of the things that kept me from trying it until now is just the box they come in- these could have been packed in something a tenth that size, and the box gives the impression that they must take up much more space than they really do. <br><br>I wonder what sort of polymer this is? Could it be Mylar? I don’t think I’ve ever seen Mylar without a metallic coating of some sort…<br><br><br>