Properties of Clay

There are 7 stages of clay drying and each has different properties

Stage 1) Raw Clay (Earthenware) -This first stage of clay is basically a muddy like powder, it comes in different colours such as black, grey, red and purple. This clay however still contains all the dirt and impurities.

Stage 2) Slip - This is Clay that has enough water in it to make it smooth and runny. Slip is normally used to patch up any holes in ceramic pieces or to join clay together.

Stage 3) Plastic - This is the stage of clay that is the most usable. In this stage it is smooth and soft enough to shape and mold but strong enough not to fall apart.

Stage 4) Leather Hard - This is the stage of clay where ceramics are half way dried, this stage is the best for adding fine detail, holes and handles as the clay will not crumble or split under light pressure.

Stage 5) Bone Dry
This is the stage where all of the water has evaporated out of the clay leaving it very fragile. This is when the clay is most easily damaged because even a slight knock or bump could destroy the whole thing. The clay is then very carefully lifted into the bisque kiln.

Stage 6) Bisque - Bisqued clay is clay that has been fired in a kiln, after this any glaze or decoration can be added to the clay before its final firing.

Stage 7) Fired - After the pottery has been Bisqued, it needs to be fired again. There are lots of different types of final firing, here are 3 of the most common:

• High Fire - This is mainly for functional pottery, like dishes and bowls, and is fired at approximately 2300 degrees to make the glaze harden to a hard glass coating. The entire heating and cooling process of High Fire takes about 3 days. 

• Raku - This process is done in a small outdoor kiln, and the pot is heated until it glows red hot (approximately 1800 degrees) and then immediately taken out of the kiln with tongs and either burning horsehair onto it, or placing it into an enclosed area like a garbage can filled with newspaper, pine needles, sawdust, or any other type of combustible material. This process only takes an hour or so.

• Pit Fire - This process involves digging a hole in the ground, placing your pots in it with wood and sawdust, and lighting it on fire. It takes about 5 or so hours to let the pots get hot enough to turn rock hard.  These pots always come out different, and sometimes need to be fired a couple of times to achieve the type of coloration you desire.