Question

A blue glass when heated will glow with:

Answer 1

I’ve been learning to blow glass and I noticed when I started to use colored glass, that when you heat it up in the furnaces, the often intense and vivid color of colored glass seems to disappear to be replaced with little but a dull orange glow. However opon cooling the color immediately reappears. Why ? It took me a while to find what I think is the answer. At first I thought it might be the dull glow simply drowning out the, say, cobalt blue but it didn’t make sense to be – the glow is not that intense and the color is often really intense when the glass is cold.