My father and I have recently made bread. The dough consists of 1/2 tbsp of yeast, 2 cups of water, 1 1/2 tbsp of salt, and 4 cups of flour. We let the dough sit overnight in a bowl covered in tin foil to let it rise but when we get up in the morning there are little pinprick holes in the Aluminum foil. The yeast does give off CO2 so I'm assuming that this is the result of gas escaping but the holes are kind of blackish around the outside... I'm wondering of this is a chemical change. I can't think of any chemical equation that would have Al+3 reacting with CO2. The only thing I can think is Al(HCO3)3...but even then I hope I'm not putting that in my bread. What do you think?