Random high-school memories

I posted this in a YouTube comment -- "That Chemist" is collecting firsthand stories of chem-lab disasters and near-disasters and narrating them -- and I thought some of my readers here might also enjoy the reminiscence. This doesn't involve any disasters (except for one experimentally-invalid lab design in a college lab class), but other commenters had mentioned cases where a "fill up a balloon with acetylene and ignite it" demonstration was rather more exciting than expected.

( Chemistry behind this solvent-proof cut-tag blast shield )