My tractor shed lights ???

[moored4]

This has nothing to do with my tractor but in my tractor shed I have acquired some 70+year old porcelain or granite ware barn lights. I plane on mounting them down the center alleyway of my shed, so I have 2 questions.

First is does anyone know how to refinish the chipped glass finish?

Second is, At the top where the wiring is they used a "pot" metal similar to aluminum but not. The internal piece and outer piece made of the same materials have grown together over time. Any suggestion on how to get these 2 parts apart? I have been putting airkoal (sp) on them for two weeks and nothing. Will post pic latter tonight! Thanks for all the help that I know I'll get!