So a few years ago I traded a small anvil for an old coal forge. This thing's a beast, but it is solid and came with an electric blower that is variable speed and still works.
Looking down into the forge area, it used to have a lot of white-yellow stuff around the fire-pot that I assumed was some sort of castable refractory. It got wet (several times) and the stuff has pretty much dissolved, so I'm not really sure what it was.
The question is this: Should I replace that stuff? If so, what should I use?