Of course, in the process of making the shell, it is advisable to cover up the end of the cup which was attached as a funnel for the bronze. If the cup gets filled with ceramic that defeats the purpose of having a wide opening to pour the bronze (try pouring maybe 50 pounds of bronze through an opening 1" square). This is usually done by putting the lid of the cup (which is simply a disposable paper cup) on the end before you begin dipping. Of course, then you get shell on the lid and in effect have sealed the cup shut.

So when the dipping is complete, you have to cut the end of the cup off. What you see lining the cup is the, well, the cup - in effect lining the ceramic cup with paper. If you peeled out the paper you would see the end of a wax sprue at the bottom. So when the wax (and paper) are burned out you end up with a nice hollow ceramic mold of the original model.

Cutting the end of the cup is done with an angle girder fitted with a diamond edged wheel specifically designed for cutting ceramic or masonry. A wheel for cutting metal will not suffice since - oddly enough to the novice - the ceramic is a much tougher material and a metal cutting wheel would get ground down in short order. However the proper diamond wheel cuts through the shell with ease although the metal part of the wheel produces flying bits of metal which manifest themselves as a myriad of hot sparks.

Hence the safety equipment. Not only do you wear a face shield and gloves (shown) but also a flame resistant long sleeve shirt and apron. CooperToons avows the necessity for the equipment. Once using the angle grinder the edge of the wheel broke and flew up, hitting the front of the face shield. Without the shield, the edge of the wheel would have broken, flown up, and hit the front of the face - period.