Refining gold from ore or concentrates is done during the smelting process. During this process, flux is used to dissolve contaminates such as metal oxides from the gold. The flux is added to a crucible with the gold that is then melted in a furnace. You can make flux for gold refining by first obtaining all of the ingredients and then mixing them together in the proper portions.
Measure and weigh 5 oz. of anhydrous borax using the digital scale.
Measure and weigh 40 oz. of silica sand #70.
Measure and weigh 10 oz. of sodium carbonate or soda ash. This will be the oxidizer for the flux.
Mix the ingredients together in a plastic container. Place the lid on the plastic container and make sure it is completely sealed.