The Laws of Pesach vol.4, no.11
Hag’olah Hag’olah is the commonly accepted method for kashering many types of vessels to be used for Pesach. This process may be used for uncoated metal utensils which have been used for cooking, serving, or eating chometz.
Proper "hag'olah" procedure is as follows: The utensil should be cleaned thoroughly - even removing rust - and left unused for twenty-four hours. If there exist any cracks, crevices, etc., in which dirt may remain, the hag'olah process will not suffice.
The utensil should be submerged in a pot of boiling water. (In theory, even a non-kosher-for Pesach pot may be used for this purpose provided that it too has been thoroughly cleaned and not been used for twenty-four hours. However, it is customary to only use a pot that is itself already kosher for Pesach for such kashering.)
As the immersion will momentarily lower the water temperature, the utensil should not be removed from the pot until the water has returned to a boil.
When kashering more than one utensil, care should to be taken to see that they are not touching each other during the immersion. Several utensils may be loosely strung together, with a few inches of string separating each of them, and then immersed slowly into the boiling water.
If the utensil is being held by tongs or the like, it is critical to change the place where it is being gripped, making certain that all parts of the utensil come into contact with the boiling water. This may be done through a second immersion, if necessary. Similarly, if the utensil cannot be completely submerged into a pot, it may be kashered in sections provided that eventually all parts come into contact with the boiling water.
If the utensil is itself a very large pot, it should be filled to the very top with water and heated to a rolling boil. At that point, a previously heated stone or heavy kosher for Pesach metal object should be tossed into the pot, causing the boiling water to flow over the rim and walls of the pot.
After the hag'olah process, it is customary to immediately rinse the utensil with cold water. If this was not done, the kashering process is valid nonetheless.
