Hints & Tips

The following hints and tips are concerned with building, and or renovating high voltage equipment.

• When varnishing coils, use standard polyurethane varnish. Give it a rub down between coats using the finest wet and dry paper, but use it dry. Before applying a second or subsequent coat, give it a wipe with a lint-free cloth moistened in white spirit. Work in a dustfree, dry atmosphere. Dust particles can cause focal points for discharges from unwanted points. Use at least five coats of varnish. A coat of clear furniture polish will help keep the surface dust and moisture free, once the varnish has hardened well. You can't overdo the preparation, take your time, you will get a better finish and better results in the long run. And finally don't drink coffee or tea when varnishing, because dipping your brush in the wrong liquid spoils the finish, and the beverage won't taste too good either (it happened to me the other day).

• If you want to be really traditional over getting a good finish on wooden items, or when varnishing a coil, then you can either make your own shellac varnish by dissolving shellac in alcohol and then filtering it (a long and tedious business) or you can get it ready prepared as french polish from any good DIY store (I personally prefer Rustins).

• If you plan to wind a coil of any size, then either build a winding rig or use a lathe. Keep the speed slow and the tension on the wire constant. Don't let the wire feed from off the end of the coil, as this introduces kinks. Many otherwise good coils are spoilt by poor winding techniques. Turns need to be side by side, don't allow one turn to pass over a previous turn, likewise don't allow kinks to form. Both of these latter points cause places where you are likely to get unwanted discharges. Smoothness of tension and spacing are important for any coil. In the case of multilayer coils, a thinf layer of waxed or varnished paper between layers will improve the insulation and the smoothness of the next layer. Be aware that in the case of multilayer high voltage coils that the layers should not go to the end of the former, but that the layers of insulation should.

• Many constructors reccomend the use of silicone sealants for a variety of purposes. My advice is don't. As the sealant cures it releases acetic acid at quite high concentration. Acetic acid is very corrosive, in particular where there are contacts between different metals (e.g. soldered joints), and in the case of highly reactive metals like aluminium. Personally I prefer the use of hot glue.

• If you want to keep a high polish on metal parts, a touch of clear nail varnish or hair spray works well (make sure you don't get it on contact surfaces obviously).

• Avoid sharp edges, rough surfaces and points on all high voltage components, they all increase coronal discharge and may cause the production of unwanted arcs. The larger the radius of curvature of components the better.