Because of if gold lost heat, gold will adhere with the crucible. If you use electric crucible or ceramic crucible, when gold was melt pour into the block. Scrap gold 5 grams can be gold 2.7 grams. A high percentage of gold is round and glossy. This pure of gold is 98.4%. If you want gold cleaner, you can boil with nitric acid about 10-20 minutes.