How can I tell if an antique cranberry red blown glass bottle is flashed or red all the way through?

Question

Obviously, I don't want to SCRATCH at the surface to see if that would reveal clear glass underneath. The pontil is polished, and I would think the polishing would reveal clear glass if it were flashed. However, there is nothing but red. Please tell me if there is a definitive way WITHOUT harming the glass.

Answer 1

No there is no way without damaging the glass

If you look at the top lip and bottom and turn on sire with bright light behind it you may see a strip of clear then it would be flashed-

but if all you are seeing is red thru and thru then i would have to suspect its not flashed-

is there a reason why you want to find out? either way cranberry glass is pretty valuable (pure gold used in getting the cranberry color)

Answer 2

If the bottom is polished and still red, then either the color is on the inside or it is all the way through. If it is on the inside then observation across the edge of the glass in the thicker parts will show a halo of clear beyond the inside color (which carries through on direct viewing.) No halo, then it is solid. The amount of gold in the glass is trivial, what makes the red valuable is the difficulting in making a good red that does not turn a muddy brown while working the glass.