Aether 2 is our reactive encasing glass, designed for superb work-ability in the flame. It is engineered to be resistant to boiling and free from excessive seed bubbles. Each pound is wrapped in white paper to keep it free from dust and fingerprints. Aether 2 has solved the production issues of original Aether and has an improved viscosity curve. It will react with silver glasses but does a better job of holding the luster under encasement. If you prefer a non-reactive clear, try Zephyr.