One aspect of clay work that is both a blessing and a curse is that the clay worker needs to contend with a lot of messy reality. To get particular glaze colors and effects, a host of natural (and hence variable) materials need to be tested, and each result under different firing circumstances and on different underlying clay bodies. Except for the fact that this process is fascinating to some, it seems improbably that any pottery would ever get made!
Here is some information about kiln, firing protocols, and the prospected materials I’ve found useful and interesting.