[Eeyore]

Timothy Daniels wrote:

"Eeyore" wrote:
Timothy Daniels wrote:

Yeah, the problem has always been that I don't have a variable
voltage power supply to "form" them

Just use a suitable series R to limit disastrous currents and bangs.

OK. I take it that "forming" doesn't have to be done
gradually, i.e. over a period of... 5 to 10 seconds, say.
What's a safe current?

5 to 10 seconds on a variac wouldn't be wise on caps that old anyway IMHO.
You might as well connect them straight.

Say allow 5W ? dissipation. At 100V that's 50mA. 2 k ohms. If the
voltage rises very slowly, there's a lot of re-forming going on.

Graham