When needed, one can Kasher utensils that are not Kosher. E.g. if one puts a Milky spoon in a hot bowl of meat it cannot be used until it is Kashered.
One cannot Kasher a utensil that has been used in the past 24 hours with hot Chametz.
Before Pessach one can Kasher certain Chametz utensils to make them Kosher for Pessach.
Kashering must be done under the supervision of somebody who has learned all the intricate laws of Kashering, when possible.
When utensils are Kashered, they become Kosher and Parev; neither milky nor meaty.
The custom is to refrain from Kashering Milky utensils to use them subsequently for Meaty, or Meaty utensils to use them for Milky.
Source: Kitzur Shulchan Aruch 46:15, 116:16, 18
נוֹהֲגִין שֶׁלֹּא לְהַגְעִיל כְּלִי חָלָב לְהִשְׁתַּמֵּשׁ בּוֹ בְּבָשָׂר אוֹ אִפְּכָא.
אִם אֶפְשָׁר יֵשׁ לְהַגְעִיל בִּפְנֵי בַּעַל תּוֹרָה הַבָּקִי בְּדִינֵי הַגְעָלָה
אֵין לְהַגְעִיל אֶלָּא כְּלִי שֶׁאֵינוֹ בֶּן יוֹמוֹ, דְּהַיְנוּ שֶׁכְּבָר עָבַר מֵעֵת לְעֵת, מִשָּׁעָה שֶׁבִּשְׁלוּ בּוֹ חָמֵץ. וְכֵן הַיּוֹרָה שֶׁמַּגְעִילִין בָּהּ לֹא תְהֵא בַּת יוֹמָהּ.
- Danny Schoemann
Tuesday, 23 Adar-2 5784
Please daven for the full recovery of the seriously wounded soldier
מֹשֶׁה אַהֲרֹן בֶּן לֵאָה בֵּיילָא
לרפואה שלמה
