About 15 years ago, I developed a highly effective technique for successfully working glass on copper tubing. I had been looking for a way to add glass to my bed frame, and wondered if I could somehow put glass on metal. Since the coefficient of expansion of copper is 80% higher than that of glass, it appeared unlikely that it would be possible to fit glass and copper tubing. Through beginners naïveté, I was able to solve the problem (see Figure 2). I have been using this technique extensively, and to the satisfaction of many clients, since that time.
In retrospect, the reason blowing glass on copper tubing works has little to do with the coefficient of expansion and fitting the copper to the glass and much more to do with the elastic limit, where Youngs Modulus breaks down and the copper deforms. After copper has been brought to a red-hot temperature, it is very deformable and will move to where the neighboring glass wants to move.