(some time later)
...and that's about all the experimentation he's got in him for today! Keltham finds today's results very encouraging! There were a lot of bizarre phenomena that nobody understood! But not a steady stream of YES or NO either! With that amount of variation, there's going to be all kinds of handles they can use to find hypotheses that compress these mysterious details!
Also they actually did manage to make materials that would burn a different color! This is very encouraging and strongly suggests that Prestidigitation chemistry can in fact be a thing!
The first target remains large-scale high-purity sulfuric acid synthesis, which would all by itself noticeably contribute to bringing down spellsilver costs and can be considered as a prerequisite step to trying to refine spellsilver out of less costly ores.
Keltham has left behind some descriptions of common chemical reactions made with identifiable materials. He suspects he may end up taking a slower day tomorrow, and has other things to do today. People could, only if they genuinely actually have the spare time and energy and don't need a day off more, try to experiment with measuring the reaction rates of known reactions. And, if they can measure those rates precisely enough to make it worth it, check to see if they can make particular reaction pathways happen faster, slower, more reliably, that sort of thing. It'll probably be easier to make flames that burn cooler rather than hotter but that's only an informed conjecture...
Oh yeah, temperature. Keltham is still trying to figure out how to build a thermometer. The last attempt exploded and was sort of a stupid idea anyways. That part's actually sorta important. They'll be doing a lot of temperature-measuring. More precise measurements mean consuming less material inputs to generate effects large enough to notice. There doesn't happen to be a Measure Temperature spell, does there?