Ash glaze ceramics: what the process involves

Ash glaze is made from wood ash, water and sometimes a small amount of feldspar or clay. It is one of the oldest glaze types in ceramic history, and it is still used by a small number of studio potters because the results are genuinely unpredictable in ways that other glazes are not.

How the glaze is made and applied ¶

The ceramicist who makes the mugs in the current Silver Raindrop collection works from a studio in County Cork using local stoneware clay. The ash glaze is made from hardwood ash that has been sieved, mixed with water to a specific consistency, and applied to the bisque-fired piece by dipping. The thickness of the application affects the final colour, and because dipping is never perfectly uniform, each piece comes out slightly differently.

The glaze is fired at 1280 degrees, which is at the high end of the stoneware range. At that temperature the ash melts and flows slightly, which is why the glaze tends to be thicker at the bottom of a piece and thinner near the rim.

Why the colour varies ¶

Ash glaze colour depends on the type of wood the ash came from, the atmosphere inside the kiln during firing, and where in the kiln the piece was sitting. A piece near the top of the kiln will have a different surface from one near the bottom, even if they were glazed from the same batch.

The mugs in the current collection range from a pale grey-green to a warmer brown-grey. Some have a slight sheen; others are more matte. None of this is inconsistency in the making. It is the nature of the process, and it is why customers tend to spend time choosing the specific mug they want rather than picking one at random.

Using and caring for ash-glazed stoneware ¶

Ash-glazed stoneware is food-safe and dishwasher-safe, though hand washing will preserve the surface for longer. The glaze is durable but not indestructible; dropping a stoneware mug on a hard floor will chip it, as it would any ceramic.

The mug will look slightly different after the first few uses as the glaze settles. This is normal and not a defect. Tea and coffee will leave a faint stain inside the mug over time, which most people consider part of the character of a well-used piece.

Each mug in the current collection is sold individually and priced at £38. Stock is limited to the current firing run; when they are gone, the next batch will come from the next kiln opening, which is not yet scheduled.