I have a similar rig but I made the "hat" from ceramic insulation mat and a stainless kitchen bowl. My burner is simple iron pipe and two T-joints, one for propane inlet and another on top of it for a fan connected by a hose from a vacuum cleaner. The fan is a real money saver as it keeps me going for far longer on a single propane tank. It's mounted on the wall on a hinge system allowing me to lift the whole "hat" to fit material in.
It wasn't too bad chemically. It was probably the cold and abrasion that made them go red. I did wear thin nitrile gloves the next time I was playing with refractory, but the abrasion very quickly tore them off.
