Rub-a-dub-dub

[rgilbert]

Elbow grease (or a good Dremel with a wire brush) might be your best bet. Buffing compounds on a buffing wheel might work, but I haven’t tried that approach. Be careful about using a pickle on the firescale — it could etch the glass.

Have you considered using stainless steel wire? It usually takes a uniform dark color inside and outside of the piece and seems to be as hard as when it went in.