So true, sir. But I think the point that has been missed is we are not talking about heat, but about how hard it is for magic to do something. If it were all about the science, it would be a easy thing to creoterram carbon dust and then regoterram that dust into diamond, which is after all, just carbon. But magic treats precious gems different then carbon dust, and has a much higher level requirement. That's not an error, that's magic. So the idea that magic has a "harder" time making lead melt then it does making other things "glow red hot" is not out of line.

The smith could "measure" heat in terms of the amount of fuel that he needs. Of course, precisely the amount of fuel etc is probably dependent on his technique, the fuel source, the design of his forge, etc, so it might not be possible to directly translate a "hotness" measure from one smith to another. But certainly for his own work a smith should be able to say: "this process is hotter than that one", even if he can't give a number to it.

The smith also probably knows it is a bad idea to try to melt iron in a lead pot, for example.

Anyway, a magus can always use InIg to determine how hot something is. (or possibly InTe would work too, temperature is a property of the material).

I think the biggest point is the following:

The line creator has openly admitted that this is in ERROR. There should not need to be any more debate on it.

In addition though, Any smith of skill would know the differences in his fire heats and how they affect metals. Does he need to heat the forge hotter or cool it off because all metals have different temperatures that are best for working them.

Oh i know that. Thats not a problem.
The problem in this case was an obvious contradiction.
Nothing saying that magic creates light the same way its created normally just as one very simple explanation.

I think it probably should be errated though(or at least taken note of so that its fixed if there is a 6th edition, and if not officially errated, at least noted with the errata so its easily known(and known that "you"/AG knows about it(i did check the errata for it before posting))), with the two swapped it works fine, you could than roughly say that you have the levels producing 100,350 and 750C with possibly adding a next level for "white-hot"(1200+C) and another for "melts any metal" or something, giving a rough but somewhat coherent scale.

The other variant would be to change "melts lead" to "melts metal", but as noted, this would make for some very nasty damage spells so might not be as good of an idea.

Thanks for the reply anyway.

Its completely idiotic. Because otherwise i just magic a bit of steel red-hot and then put the lead on it, and then i suddenly get lead melting very very fast. Making the higher level spell not just useless but utterly impotent. And far more problematic, how would you describe heating something one level higher still?
Doesnt make even a shred of sense, not now and not in the year 1200.

Leave it mate. Trot past the Black Knights with your coconuts shells going clipperty clop.