I'm smelting iron oxide heavy, gold bearing material using Chapman flux with some fluorspar added as flux thinner. I'm using silver as a collector metal to pull out gold during smelting process. After smelting, I end up with a silver/gold amalgam. Using specific gravity as a measure, i estimate that the resulting metal is about 20% gold on average.
Here's the problem. At times, I end up with less metal by weight than I started with. I must be leaving some silver and probably gold in the slag and I don't know why. I could use some help to develop a better understanding why such a problem might arise. What are the smelting process variables that I should be examining/tweaking?
Some more details describing my current approach.
1. Time: After material is molten, I hold at for 30 mins.
2. Temp: Max temp is 2700 to 2800 degrees Fahrenheit.
3. Flux to concentrate ratio: 1.5 to 1.
4. Fuel: forced air, propane.
5. Crucible: clay bonded graphite.
Here's the problem. At times, I end up with less metal by weight than I started with. I must be leaving some silver and probably gold in the slag and I don't know why. I could use some help to develop a better understanding why such a problem might arise. What are the smelting process variables that I should be examining/tweaking?
Some more details describing my current approach.
1. Time: After material is molten, I hold at for 30 mins.
2. Temp: Max temp is 2700 to 2800 degrees Fahrenheit.
3. Flux to concentrate ratio: 1.5 to 1.
4. Fuel: forced air, propane.
5. Crucible: clay bonded graphite.