Kashering glass plates

Question

We bought from eBay glass fish-shaped plates, manufactured by Arocroc (France) in 1970 or so. The listing had "unused" in the description but that is not certified. How does one kasher glass plates?

Answer 1

The Sephardic opinion is that glass never absorbs, so it never has kosher issues.

Ashkenazic opinions vary; a lenient (albeit very authoritative) one is that of Rabbi Moshe Heinemann of the Star-K:

ANTIQUES

Q: Can one purchase and utilize used or antique crystal bowls or glasses?

A: Yes.

MEAT / DAIRY MIX-UPS Q: If someone poured hot milk on a cold meat glass/pyrex utensil or hot meat on a cold dairy glass/pyrex utensil, what should be done? A: The dishes should be washed off and not used for 24 hours. The glass/pyrex utensil can then be used as it was originally designated.

Q: If someone poured hot milk on a hot meat glass/pyrex utensil or hot meat on a hot dairy glass/pyrex utensil, what should be done? A: Ask a Sheilah from your Rav.

But as always, ask your rabbi!