I bought an assortment of objects to try as top loads on my small, tabletop
coils. One is a oblate doorknob. It looks like brushed stainless steel, but
it might be brushed aluminum. The knob does not stick to a magnet. It seems
to have a heavy coat of clear coat. typical for a closet door knob.
In place, it emits the usual sort of long, tendril-like streamers. So far,
so good. Then I noticed small sparkles popping up on the knob surface while
the coil operates. These are little, bright white pinpoints of light that
pop up, sparkle a very short time, then vanish. They reappear all over the
surface of the doorknob. They're quite different from the streamers, which
are long, lavender or purplish, and moving. I thought the sparkles might be
where a streamer was trying to get through the clear coat and failing, but
examining the knob with a magnifying glass I can't find any perforations in
the clear coat that match where the sparkles appear.
What could these be? I am using a spark gap type coil, powered by a 7.5 KV
NST, my own design dry Leyden jars (2 nF), with the lower end of the
secondary joined to the lower end of a helical primary, etc.