Homebrew PCBs

>
> It can cause problems, as toner generally contains carbon black which
> is conductive. In most circuits this may not cause a problem, but in
> high impedance and RF circuits it can very well cause problems.
>

You can repair potentiometers with toner.
I thought it is the iron powder acting as "developer"
(transfers toner to photo drum)

I didn't know that is carbon black?

ST