They are cheap, colorful and when filled with gelatine, they break apart in spectacular patterns.
This is a fairly large 9cm diameter bulb, filled with clear gelatin with a small brandy snifter balanced on top.
The bulb had a hidden firecracker inside. I like the intricate patterns of the breaking bulb and the cracks just starting on the glass.
Cracks move fast in glass, about 6000 feet per second, so catching cracks just forming is pretty lucky.