I'm new to smelting. I've come across some black sand that I want to assay and decided to build a smelting furnace. My problem is that it's not quite getting hot enough to melt the sulphides. The flux melts but the material just gets gooey and orange. I'm using a lead collector metal and Chapman flux. Here are some photos of my home made furnace. Maybe someone can suggest any improvements to get a few hundred more degrees out of it...