Kitty litter is not used for fluxing. It is a heat barrier and it keeps the metal from oxidizing and forming a scum that many guys skim off, thereby losing tin. A wooden stick is used for fluxing. I use a piece of cedar house siding about the size of a pencil. One of the guys here said that fluxing can be done with anything that will form carbon. The stick does that. In my Lee 10 lb. pot I use 4 teaspoons full of kitty litter.