Crucible. You will need to replace the crucible periodically. Depending on the quality of the crucible, its lifespan varies greatly. The life of the crucible may be used a dozen times, or it may be close to 100 times. You can also make a crucible out of a suitable refractory material, which costs less.

In short, you should check the crucible every time you are done using it. If you see damage and breakage in it, replace it promptly.