It's looking like " Plan B " time!   

You could use a disk made from 5 mm Plexiglas https://en.wikipedia.org/wiki/Poly(methyl_methacrylate).


- On both sides of the Plexiglas disk you put a metal plate with wires to your HV-power supply.

- The HV-power supply stays outside the baking oven, but the Plexiglas disk with the metal plates is put inside the backing oven. (Because of the wires leading out from the backing oven the door of the backing oven might be open a few millimeters. But that does not matter.)

- Heat the backing oven to 150° C (300° F) and let the Plexiglas disk remain under HV tension for at least 2 hours. (The metal plates and the Plexiglas disk in between should be placed in the oven horizontally and insulated with e.g. a ceramic plate from the metal of the oven. Also check that the insulation of the wires supports 150° C.)

- Then remove the Plexiglas disk in between the metal plates from the oven and let cool under HV-tension (this is important to "freeze" the charges in position).


The melting point of Plexiglas is 160° C (320° F) and it should be kind of soft at 150° C, but should not melt. In the soft Plexiglas the charges can wander to opposite sides of the disk near the opposite poles.

That also works with other plastic materials, but you have to know the melting point. A lower melting point is more practical, therefore I suggest Plexiglas.

I have the impression that you overestimate the charge in an electret. The charge is rather small. Rubbing the surface of Plexiglas with real fur gives you a much higher charge. But this charge will only hold a few hours. In dry air it holds longer. Once you have put a charge on the surface of a Plexiglas disk by rubbing with real fur, do not rub it with anything, only make contact straight down and break contact straight up.

Also, the charge in an electret is first lost at its outer surface, and most easily by rubbing it with something. The charge of an electret near its surface is lost by mechanical action. The charge inside an electret is less useful than its charge near or at its surface (because its strength diminishes by the square of the distance).


All products that contain an electret have the problem that the charge is lost over time and always in a shorter time as advertised. This is the reason why electrets have never been widely used.


Greetings, Conrad

Actually electrets are practically ubiquitous and when made properly do not lose their charge. All of us probably have several electrets in use in our own homes and laboratories right now.

I make electrets with caramel, aluminum or anodized iron and carbon blackened copper, they give me between 0.5 and 0.7 volts, but they do not need to be powered during cooling