Back to top
GENERAL GUIDELINES (Chart Below)
If a utensil is used with hot food that is non-kosher, chametz, milchig/dairy, or fleishig/meat, that negatively affects the utensil’s status, and before it can be used for kosher, Pesach, or pareve (respectively), it must undergo a process known as kashering (or hechsher keilim). Two common forms of kashering are hag’alah (for flatware) and irui kli rishon (for counters and sinks), as follows:
Specialized forms of kashering (known as libun kal) are used for ovens and stovetops. Another form of kashering, known as libun gamur, is not practical for most consumers.
Some reasons why kashering might not be allowed for a specific item are:  it contains ceramic or glass material for which hag’alah is not allowed;  there is a concern the item might break during kashering (and, in turn, this might lead the person not to perform the kashering properly);  it has small holes or crevices where food might get trapped;  the item requires libun gamur or some other method of kashering which is not realistically possible to perform.
The cRc listings for specific items incorporate these guidelines and list appropriate methods of kashering where possible.