Let's try it.
And if quartz doesn't work out of the box, let's try Prestidigitating it.
Keltham's got to remember to just cheat the shit out of everything, there's no point in not cheating when you've got magic.
Can somebody tell him about 'bound fire elementals'? If Keltham is right that they have max temperatures rather than max added heat, keeping the sulfuric acid process at the reference temperature (above water-melt by 450% of the difference between water-melt and water-boil &c) could be as simple as getting exactly the right quality of 'bound fire elemental'.