Nice. When I had a go at casting brass, under close supervision from my mentor, we used powdered glass as a flux which melted and sat on the surface of the molten brass protecting it from atmospheric oxygen. We had to be cautious because the laboratory we were doing this "experiment" in had a smoke sensor linked directly to the site fire station and there was always the risk of an eager fireman crashing through the door, axe in hand.
Thanks for the video, your simple but effective set up is very encouraging.
Rod