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It seems to me that there are some interesting things which are done in virtually every kosher Jewish home that may have no basis in halachah. I think that having separate glasses for meat and dairy are unnecessary.

Is there a halachic requirement to have separate glasses?

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Ok then. Really, the better way to do that would have been to edit the question yourself, rather than wait for others to do it, but that's no big deal. -1 removed. – Shokhet Jul 17 '14 at 18:14
I read somewhere that the reason that glass was historically not an issue was because it broke if it was exposed to high enough temperatures, so they couldn't make it hot enough to 'transfer'. Now that glass can withstand higher temperatures, the status quo is called in to question. – Baby Seal Jul 17 '14 at 18:35
@Shokhet - Chiddushei Torah was probably busy creating other "Chiddushei Torah". Sorry but it's a GREAT user ID! Anyway, I liked the question, so I decided to edit someone else's chiddush. Got all that? &-* – DanF Jul 17 '14 at 20:35
@Baby Seal I've personally heard taboo Belsky say that. The only example he was able to think of where a glass cup is used as a kli rishon was maybe when people leave tea bags in a cup to have tea sense on shabbos. Problem is it's not bassar or chalav. Also, its not a given that people leave it where is really yad soledes bah. But said we should still be machmir. – user6591 Feb 2 '15 at 19:26
up vote 2 down vote accepted

There is a reason for it.

The Mechaber in OC 451:26Says:

כו. כלי זכוכית אפילו מכניסן לקיום ואפילו משתמש בהן בחמין אין צריכים שום הכשר שאינם בולעים ובשטיפה בעלמא סגי להו. הגה: ויש מחמירין ואומרים דכלי זכוכית אפילו הגעלה לא מהני להו וכן המנהג באשכנז ובמדינות אלו

My loose translation:

Glass vessels even if one stores in them and even if they were used for hot things do not require any hechsher, because they do not absorb, any rinsing is sufficient for them. The Rema says: and some are stringent that even Hagala does not work for them, and this is the custom in Germany and these regions.

See MB there that this applies lichatchilah even to glassware which is usually used with cold.

The above only refers to Pesach, where the psak generally follows a more strict opinion. (There is a discussion in the Acharonim about what the Ashkenazi minhag is by regular kashrut).

By regular kashrut there is certainly room to be lenient in some situations, but one would imagine it preferable for one to follow all opinions in his own home when there is no major financial cost in doing so.

As always ask your LOR for practical advice.

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This would be true if drinking hot chocolate and chicken soup in the same glass. What about apple juice? – Double AA Jul 18 '14 at 0:29

I heard from a Rabbi, a popular Halachah teacher in Bais Yaakov high schools, that while essentially one would be permitted to use the same glasses for milk and meat, nowadays it is not the custom for two reasons:

1) Glasses may be used for actual hot milk and meat. Or, they are often exposed to hot milk and meat in the dishwasher.

2) There is a concern that the glasses may not be washed properly, and there may be grease on the rim of the glass.

3) Glasses nowadays are cheap, and it is easy to have two sets.

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