Re: [TCML] party cup capacitors

[<mrapol@xxxxxxxxxxxx>]

Leyden jars were my introduction to the high voltage hobby. I built a lot of 
them, made of different found objects, foil, metal tape, etc. My ultimate 
design (so far) is based on soda cans and drink mix canisters:

http://www.instructables.com/id/Leyden-Jar-Battery-for-Tesla-Coils/

The canisters are polypropylene. With proper preparation, you can insert an 
aluminum soda can, coat the outside with foil tape, and make a pretty good 
capacitor. The first ones I made were before I started coiling. I charged 
them from a Wimshurst machine, and they were pretty scary. They hissed 
menacingly from corona loss; in the earliest version I did not insulate the 
top of the can with a thick layer of wax. When they arced over they emitted 
thick, loud, hot sparks which were more intimidating than the arcs produced 
by my other HV equipment. Spark coils and later Tesla coils make bright, 
continuous discharges which can be pretty and fascinating to watch. The soda 
can Leyden jar was like a poisonous creature ready to bite. I never took a 
direct jolt from them, but I have been stung by residual charges.

Anyway, the soda can design works pretty well. It's cheap, though bulkier 
than this party cup design. No oil, no liquid makes it light too. My small 
tabletop coils are modular so that I can swap out components for comparison, 
and I definitely see a difference in performance between my jars and 
commercial caps. (I use Soviet made ceramic doorknob caps made for HV radio. 
They work very well). I would estimate the doorknobs are 30 to 50% more 
efficient. On the other hand, I have never burned out any of my Leyden jars, 
and I have destroyed a small bucket full of commercial caps. None of the 
Soviet doorknobs--they're tough.

Paul 

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