How to make DIY high voltage capacitors. I start by showing a few different high voltage capacitors I’ve made over the years followed by an explanation of how denser electric field causes breakdown of the capacitor dielectric/insulator. I then show what the voltage rating on commercial capacitors means. I next show how to find breakdown voltage, also known at dielectric strength, online and use it in calculations for how thick your dielectric should be. That’s followed by a breakdown voltage test with a homemade high voltage power supply, an analog volt meter and an ammeter. I then show how the shape of capacitor plates influences breakdown voltage, as well as the effect thin plates has on ionizing air. That leads to using corona dope, resin or wax to insulate the capacitor plates. In the final breakdown voltage demonstrations I show the use of current limiting resistors and lastly how standard breakdown voltage tests are done.