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.
It was the 70s… we chewed on lead blinds for fun, threw sharp lawn darts at each other.
Today kids are stuffing their balls with plastics.