Miscellaneous

Apart from the aforementioned special parts (caps, resistors, rectifiers), many everyday things prove useful.

To suppress corona (spraying) from high voltage terminals etc, all kinds of sufficiently large and round conducting objects are suitable: spherical door knobs, old hot-water warm bottles (flea market), ball-bearing balls etc. Flexible aluminum duct is very well suited for nice toroids, not only for tesla coils. In general, the lower the surface curvature of an electrode, the higher the voltage where corona starts.

Good insulators are plastic tubes (for drainage or electrical installations), those plexiglass rods used to open or shut curtains, empty felt pen cases etc.

For glueing, potting and filling of small volumes, epoxy resin is very useful. It is also a good dielectric. Silicon compound is also useful but cures very slowly. Polyester resin can be used to fill larger volumes. Be careful not to use too much hardener, otherwise the mixture might harden before air bubbles are out. Also, it might become surprisingly hot, enough to melt plastic. Paraffin insulates well, but contracts significantly when solidifying, leaving cracks or bubbles.

Graphite spray (used to repair CRTs, available from electronics stores) can be used to make surfaces conducting. Apply thinly and polish with soft cloth or paper to obtain less fragile films. Grapite layers are not suitable for large currents, which are present e.g. in spark discharges. Aluminum duct tape or aluminum foil and adhesive spray can also be used to make surfaces conducting. Rub with paper or spoon to smooth the surface.

High voltage cable can be made by reinforcing normal cable with soft PVC tube. Alternatively, just put a wire (for good conduction) through the tube and fill with water or oil (to prevent corona). Oil stops corona due to its increased breakdown file strength compared to air, water does the same by reducing the field strength on it´s surface. For non-insulated high voltage leads, copper tubing is suitable.

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