On Fri, 13 Mar 2015 15:57:07 -0000, "gareth"
wrote:

Me and a friend made up a capacitor (really a condenser seeing as
the use to which it was put) by rolling up aluminium foil in between
sheets of polythene for his Tesla coil, but the capacitor failed because
of breakdown in the inevitable air spaces in the tightly-wound wad,
the sparking then causing the polythene to burn and thus result
in a shorting out.

Finally did it with aluminium foil laid between sheets of glass and
we got sparks several feet long from it, using an 11kV pole pig
in reverse as the drive.

OK I'll bite.. for what purpose?