Similar in construction to frost upon a winter window, and known, probably as a firing fault, in ancient China, this glaze style was accidentally re discovered during the eighteenth century in the great European factories of Sevre and Meissen. This glaze also appealed to the studio potters of the Art Nouveau period and was progressed in nineteenth century America by Taxile Doat and Adelaide Robineau. The industrial kiln masters of the day soon discovered that although possible, the whole process was so technically challenging to mass production that they ceased to develop the method, and little or no crystal glazed work was produced between 1919 and the 1960's. Latterly only small scale industrial production has been attempted, and few modern studio potters have chosen to take up the challenge.

The effect created by these glazes is singular, and the loss rate high as the potter breaks all the conventional firing rules to produce this outcome. Sometimes kiln losses can be as great as 70% between the first and last firing stages especially when testing new recipes and clays, and the potter has to be phlegmatic and accepting of the outcome when the time comes to open the kiln lid.

A heavily fritted Glaze, containing large amounts of the crystal forming elements - Zinc Titanium or Rutile, plus colouring oxides is applied to the piece by brushing or spraying, and the work glued to a saucer made of matching clay, which fits the base of the piece as closely as possible, before firing to approximately 1270 degrees celcius in an oxidising atmosphere - a temperature well above the norm for the base ingredients. A saucer is required because it is necessary for the glaze be extremely molten at the top temperature to produce an environment suitable for crystals to grow. This high melt inevitably means that, if not prevented, the glaze runs straight off the pot on to the kiln shelf.

Once top temperature is reached, the firing is stopped abruptly to cause first, a very fast cool down to about 1100 c, after which the very slow, regulated cool down period required to develop the crystals, which form as zinc and silica bond together in the liquid glaze.

After the kiln has reached ambient temperature the work is removed, usually firmly attached to the catcher by the glaze run off. The pot must then be removed from the catcher, and the excess glaze run ground away, using a gas torch, glass cutter, or an angle grinder, and finally a diamond grinding disk to smooth the base. During the course of this process much work can be lost, as the tension between the glaze, the pot and the catcher causes severe stress to the piece.

However, the end results can be spectacular, always unique and a source of constant inspiration and joy to the potter.