If you have never worked with clay before please take the time to read the information below.

STORING CLAY

  • You don’t need to store clay anywhere special, room temperature is fine, just keep it wrapped up or in a plastic box and away from direct sunlight.

 

WASTE CLAY

  • If you re-use clay you need to be very very careful not to trap air or it will explode in the kiln.

  • Alternatively you can return to us to recycle, please dry it out first.

 

CLEANING; HEALTH & SAFETY

 

  • Clay-dust is very bad for you, so make sure you clean your work station thoroughly with water.

  • Don’t wash clay down the sink, you’ll eventually block your pipes. Wash everything into a tub and then throw into a flower bed or flush down the toilet.

  • Oxides and glazes are toxic to marine life, so wash these in a jar and when it's settled out after 3days you can pour off the water and scoop the sludge into the bin.

Pottery Terms​

 

Shrinkage

 

Clay contains 20-30% water, so as it dries and goes through a firing, it shrinks by up to 30%. Shrinkage is the main thing you need to control in pottery, ensuring that pieces joined together dry and shrink at the same rate, otherwise you'll get cracks.

 

To achieve this it helps to ensure work is roughly the same thickness all over (if this isn't possible you can wrap thinner areas in plastic as the piece dries, to even out drying) and that when you join parts together they have been drying for the same length of time, so have the same water content.

 

 If you are worried about any of this ensure your work drys slowly by wrapping it loosely in plastic.

 

Clay Firing Temperatures

 

Earthenware: Low-fired ware (under 1050) usually still porous after firing—must be sealed with a glaze to be functional.

 

Stoneware: Vitreous ware fired at 1050 to 1326 degrees celsius, literally as hard and durable as stone. We fire to 1240.

 

Vitreous: transformed into a solid state (a non-crystalline amorphous solid to be exact) where it is impermeable by water (our clay is stoneware so is vitreous after firing).

 

Porcelain: High-fired vitreous clay containing kaolin, silica, fluxes, and often ball clay to increase plasticity, with total clay component not more than 50%. Usually pure white in color; some porcelains may fire translucent where thin.

 

Grog: is added to clay to reduce shrinkage and give structure for throwing or handbuilding. Our standard clays standard contains 10% fine grog.

 

The building, decorating and firing process

 

Pottery goes through at least two firings. Bisque firing is the first low-temperature firing, during which clay becomes solid without vitrifying, so it is still porous and can take glaze. The second firing (where glaze is usualyy applied) takes the clay to full maturation temperature, which in our case is 1240 celcius.

 

Coloured slips are made from clay, pigments and water and are added before bisque firing, when the clay is still damp. 

Underglazes can be applied either to greenware (unfired) or bisque fired ware.

 

Glaze is applied to bisque fired ware and you can either purchase painting glazes fro us to apply yourself or pay for work to be dipped. Glazes have a high proportion of melting ingredients (fluxs and silica) so they behave more like glass than clay.

Clay in different states

 

Green: clay in any state before bisque firing. As a general rule slips can only be applied to green ware, glazes can only be applied to bisque fired ware (these rules like any can be broken, but only if you understand the results).

 

Slip: clay in a liquid state (used for decorating when colour has been added)

 

Plastic: wet and pliable (straight out of the bag)

 

Leather hard: when the clay has lost much of it's moisture and is, well, leather hard :-) like a hard cheese and the ideal stage for adding decorating slips.

 

Bone dry: when the clay has lost all of it's moisture, it is at this stage it can be bisque fired and it's too late to add decorating slips.