Spark gap not firing

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Matus-at-snet-dot-net by way of Terry Fritz <twftesla-at-uswest-dot-net>" <matus-at-snet-dot-net>

Hello all, I am attempting to build my first coil on my own.  I have a 15kv
neon sign transformer at 30 milliamps.  I tested the transformer on a
rudimentary jacobs ladder to make sure it works (and cause it looks cool to my
friends), I now have it wired in series with the primary coil, which is made
from 1/4" refrigerator tubing and consits of 6 turns at 1/2" spacing with a 6"
inner diameter.  I have a calculated inductance of 10 - 11 microhenries I
believe (dont recall the exact number) It is also wired in series with the
capacitor.  The transformer was calculated (by wintesla) to need .0053 uf.  I
built a foil stack capacitor composed of five aluminum flashing plates that
were 5" x 7"  sandwiched in between them was a rubberized adhesive coating
which I do not know the exact K value for.  The rubber adhesive was four inches
across and covered the length of the aluminum plate, giving a capacitor area of
4" x 7". The rubber layers is about 1/64" of an inch across. My Handbook of
chemistry and physics has the K values for some rubber materials between 3.0
and 3.8, I dont know exactly what kind of rubber this is.  Anyway, without the
capacitor, the spark gap fires at up to 1/5" or so once the air is given a few
seconds to ionize.  With the capacitor I can not get the spark gap to fire at
all, even when it is shortened up to about 1 mm or less.  I know the capacitor
is storing a charge because I have to disharge and hear a spark.  So why is the
spark gap not firing?  My rough estimates of the thickness of the layer and the
K value will throw off my capacitor total capacitance, which I tried to get
close to .0053.  So whats going on here?  Do I need more plates?  Is the
voltage of the capacitor not high enough?
 
Any help would be appreciated
 
Thanks!
 
Michael