If I recall correctly, electrolytic capacitors have to get "burned in" during manufacturing to make them work.

A current is passed through the capacitor and a thin film of oxide is built up in one of the terminals, according to the polarity. This is why electrolytic caps have polarity, if you use them with their polarity inverted, you flake off that oxide layer and thus short them out.

A free running current in that electrolyte boils it off, and you get an exploding cap