To use a vessel on Pesah that was used during the year for Hames, it must first undergo koshering through Hag'ala, which literally means to extract or purge the Hames that has been absorbed in the vessel. The method of extraction depends on how the vessel was used. The famous rule of the Gemara is "K'bol'o Kach Polto"- the way the vessel absorbed Hames is the way it extracts. That is, if the vessel was used only with fire without water, it must be made Kosher with fire. If it was used with boiling water, then it must be extracted through boiling water.
The type of extraction is based on "Rov Tashmisho"-the majority type of use. For example, it is possible that a fork was used directly with Hames in the fire, but the majority of times the fork was used to stir liquid in a pot. Therefore, it is sufficient to Kosher the fork with boiling water.
The question is how can the lesser form of extraction, boiling, work, if even one time it was used directly in the fire? The Rama MiPano (R. Menachem Azaria, 1548-1620, Italy) says in his Responsa (97) that he was asked this question by his students. One answer he brings from the scholars in the Yeshiva is that this rule is limited to cases in which there is only a possibility that it was used directly in the fire, but if there was even one certain instance, it would require extraction via fire. The Rama MiPano brings proof that this rule of the majority applies even to cases in which it was certainly used with fire. Therefore, he offers a new answer to the question and says that the rule applies only to cases in which the vessel hasn't been used in the last 24 hours, i.e. it is not "Ben Yomo, and therefore by Torah law any Hames absorbed in the vessel is already "Pagum"-lost its effectiveness. Since it only needs koshering by Rabbinic law, "Hem Amru V'Hem Amru"-they instituted the problem and they determined the solution, whereby the extraction follows the majority use of the vessel. This approach is also taken by the Peri Hadash ((Rav Hizkiya Da Silva, 1656-1695)
It follows that if the vessel had been used for Hames in the last 24 hours, then it would be koshered according to the strictest use done with it, even if only one time. In short, by waiting 24 hours since the vessel was used with Hames, the vessel may be koshered with the method based on its majority use.
