It made bubbles of, per wikipedia,
polyvinyl acetate dissolved in acetone, with ethyl acetate plastic fortifiers added. The acetone evaporated upon bubble inflation, leaving behind a solidified plastic film.
Which looked like,
↓↓ VOLUME WARNING! LOUD DISTORTED AUDIO!! ↓↓
And here’s a 1970’s commercial. Especially headphone users, would recommend starting low and easing into it.
My bad. I just looked it up and copied the Wiki address on my phone. Didn’t realize Google would add an extra step in the middle.
Though, I’m not surprised by it either.