STONE TECHNOLOGY, SPECIFICS

The usual way to make round object to a high precision is to use a lathe. While the object is rotated quickly by the lathe, a stationary chisel is used to cut away the material, automatically giving a round surface, like a potter does using a turning wheel and his hands. However, this technique depends to a large extend on the material being flexible. The materials used in lathes are mostly metals, that may seem very much harder than the clay of the potter, but in fact pure metals are quite flexible, their seemingly hardness stemming only from the fact that it takes a big force to stretch them, but if you apply such a force, they stretch considerably. One can also make harder, brittle, metals like cast iron, by mixing them with other materials. But a material like cast iron is notoriously difficult to work on with a lathe, if at all.

The point is that stone is even more brittle than cast iron. This makes the forces necessary to cut it much higher, and the possibility of breakage even more. It would be hard to imagine how one could use a lathe to achieve the outside surface of the vase in the picture, it is really inconceivable how this could be done for the inside surface, while having to work around a corner.