Northstar Onyx boro glass is the smoothest most saturated black in the Norsthar palette. It is well suited for stringer applications and blown work. It is a green based black and in certain lights it has a slight green tint. Onyx can be worked hot and long without boiling issues and it is not sensitive to reduction. For best results keep it in a neutral flame. It looks great as a backing for NS-013 Amber/Purple and by itself. It is great for backing dichroic, gold, and silver fume.