The patterns you see in the glaze of these pieces are real zinc/silicate crystalline formations that grow randomly in the glaze during the firing process. Every piece is unique and has it's own color, character, and crystal formations. More information available on the page.
Few potters in the entire history of the process could lay claim to being a Master, which I certainly do not. Macro-Crystalline glazes are one of the most difficult pottery process' to produce. The glaze is incredibly fickle and often just does not behave as expected. There are many steps between a raw ball of clay and the finished product, any of which could spell disaster. However, when it all comes together, the results are nothing short of spectacular.