Primitive Technology 2.5 m Natural draft furnace experiment

There are many types and mixtures of clay.
There are the high alumina clays - to make clay crucibles from (got some of these clays) and there are clay mixtures for fine china, there are also clays with high melting points "fire clay" - and then there are dirty surface clays that have mixtures of a whole heap of things in them - which generally work to lower the overall fusion and melting points - which I have turned dirt into glass...

This experiment shows, as the clay gets hot enough, it starts to melt and fuse and liquify and peel off internally into a dirty glass.....

You learn by doing.

This is part and parcel of learning about materials and combinations of materials that have high melting points, and physical properties.....