I just find it funny that the only way to get Potash(ium) is the (semi) industrialized way, and more-so odd that the traditional method of burning wood and leaching the ash and then boiling off the water is not an option.
It could easily be locked behind copper by way of requiring barrels to leach the ash. Alternatively, ash could just be used in place of the ground sylvite in the current recipe, but then it could be done with just clay.
As for the ash, I could see it being gained by intentionally leaving open a charcoal pit and then collecting the resulting piles of ash instead of charcoal.
Any of these ways the yield would be small, requiring something like:
10 ash : 1L of water —> 1 potash
(roughly the 10% by weight that wood ash is)
Thoughts?