Thanks Al for taking trouble on all those calcs. I shall try various light bulbs but I do seem to recall that when I first used 60w bulbs they reached max brightness well before my variac was up to 240v, so switched to higher wattage.
I was nervous about what might happen to my GU81s if the 60w blew.
BTW, I am getting an ozone mask...…
….all coilers should wear one when sparking Bach.
What with EHT, RF and ozone dangers it's safer and better audio quality just to listen to a CD!