Question: If I go to someone’s house and that person does not keep kosher, can I have a cup of tea there in a china cup which is presumably glazed on the outside, (as I think all cups are nowadays)?

Answer: If tea was poured into the cup, one would be permitted to drink it (unless one knows that the cup had been used for non-kosher, hot food in the last 24 hours—we do not assume that it was). Asking for a cup of tea, or pouring it yourself, would not be allowed.

Simply put, the reason for this is that you may not intentionally use a non-kosher utensil for hot food. In case it was done unintentionally, then the kosher status of the hot food or drink depends on the following: Is the taste of non-kosher food or drink (already absorbed in the utensil) capable of affecting the food or drink placed in the utensil? The conditions for the latter are complex, and beyond the scope of this correspondence. Please speak to a local kosher authority for more details. Suffice it to say that, in this case, the tea would be permissible, presuming you fulfill the conditions mentioned in the previous paragraph.

All the best!

Rabbi Azriel Schreiber