I've known some people to do water scrying using their cauldron. I just use mine though for burning charcoal incense and so do several other pagans I know.
So not to ruin the cauldron, fill it at least a quarter full of sand first. Place your charcoal in the middle and then add your resin, crushed herb or powdered incense on top. And when I say charcoal, I am not referring to the type used for outdoor cooking with a grill. There are special made charcoals used for incense. Health food stores and new age shops normally have them.