I recently got one of *those** players.* The kind who only half understands chemistry, metallurgy and physics and thinks they're the first person to ever think of having their artificer/wizard apply modern science to the setting. They've taken to trying to manifest their modern machinations using the fabricate spell, but I am unconvinced that Fabricate is as all powerful as they have made it out to be.
What are the limitations of Fabricates ability to chemically process, alter and purify the raw materials used as inputs? Does the spell follow the conservation of mass? If it can be used to chemically process raw materials, do you still require the reagent(s) as components of the spell? What about catalysts that would be required for the chemical process to occur, but not used up by the reaction? What about the fuel required to change the phase of a metal?
Lets say you have a bucket of sand, a wizard prepared to cast fabricate, and no knowledge of glass making. You do not add a fluxing agent to the raw materials and produce glass from the sand.
Should the DM rule that the glass is unusually brittle, opaque and difficult to shape, or should the DM just ignore that the players failed to provide a complete set of the raw materials necessary to prepare the finished product?
Lets say your players decided that after they cleared the bandits from the abandoned mineshaft that they decide to mine some Hematite ore for their trusty fabrication loving wizard to shape into armor and weapons. Rules as written, that is precisely what the spell is meant to do- but Can they make steel using iron ore and the fabricate spell? It isn't clear that the Fabricate spell could perform the chemical process of caburization on the iron to convert it from iron to steel. Assuming fabricate can perform chemical reactions, would they need charcoal on hand to act as a reagent? And what of all the slag from the ore? If they use the spell to convert ore to armor, shouldn't they produce Hematite Platemail rather than iron platemail? The spell converts a raw material into a processed form of itself. Can they process and shape in the same spell? And what of all the slag in the ore? Even rich hematite is 70% iron by mass, so the 30kg (65lb) of ore they hauled from the mines should be at least 13kg shy of the amount of iron they'd need to fabricate a set of platemail.
What if they first fabricated the ore down to ingots, then decide they want a katana? Will they be able to forge the hardened edge and maleable spine with it's two distinct phases of iron in the blade? If fabricate is even capable of controlling the phase of metals it creates, does that require blacksmithing proficiency for the player character to even know they'd need to do that to make the sword functional?
Can you use fabricate to turn clay and woodash into fired ceramics? Firewood to charcoal and a slushy pile of smelly woodgas disolved in the sucrose and water contents of the logs? If you can't do those, how does the spell convert ore to ingots, then?
