George E. Cawthon wrote:
snip
Lye acting on the aluminum creates heat and bubbles, increasing the
possibility of moving mass obstructions.

Lye plus aluminum plus water creates hydrogen.

When I was a curious lad, I used to place a tablespoon of Drano brand
lye in an old soda pop bottle along with some water and then stick in
strips of aluminum foil and place a balloon over the mouth of the bottle
and the balloon would fill up with hydrogen. If you add too much lye,
it will generate enough heat to crack the bottle, so be very careful and
start with small amounts.