Here is another type of high voltage capacitors - a Salt Water Leyden Jar!
Don't know what a leyden jar is? No worries! Read here on Wikipedia!
The water leyden jar is easier to make than a normal leyden jar because putting foil tape perfectly on the inside of the container can be very difficult. If the foil tape job is messy, it can cause a lot of corona discharge, therefor draining its charge very quickly. So instead of having a hard time of perfectly putting foil tape on the inside of the container, just simply pour salted water in!Disclaimer:
The leyden jar is a high voltage capacitor, high voltage capacitors are one of the most dangerous things you could ever use in electronics. A large charged leyden jar is potentially lethal if you touch its live terminals, and a small charged leyden jar can cause injury and it still be lethal in some ways. So, I am not responsible what ever you do with this information and leyden jars.