Macro-crystalline glazes have flower-like surface crystals that seemingly bloom over a background of a different colour. Small variations of each individual component oxides can cause a dramatic change in appearance after firing, hence warranting the need for numerous tests to finetune colour and crystal distribution. The firing cycle – a very fast rise to top temperature and a very fast drop to crystal growing temperature – is extreme in terms of pottery production. This places a huge strain on the kiln and the materials, resulting in high failure rate and equipment wear and tear. (Photo source: Crate and Barrel)