Crucibles are used in a laboratory to hold chemical compounds that are heated to extreme temps. Recently, we had replaced our crucible. The crucible keeps the glass from leaking into the furnace. Furnace crucibles come in different sizes and can be made out of different material such as clay graphite and silicon carbide, etc. Whenever the crucible is broken is it is best to replace it before too much glass or metal gets into the furnace. Its best for the crucibles to be change at least annually or semi-annually. Heres a couple of images from our recent crucible change.