Alternative Filaments

Just trying to think outside the spool. There are Bismuth/Tin pewters that melt at 200 C, also other lead containing alloys.They would probably be flexible enough to pass through the extruder if extruded to 1.75 mm. There is even mention of low temperature glass not much above 200 C.At a lower temperature one might think of investment casting wax. I cannot think that these thoughts are anything new.