From wet clay to finished project ….
Wet Clay –
comes out of the mixer. We use it to create almost all projects by hand or on the wheel. It is very ‘plastic’ and flexible. We make the project in wet clay when done molding it and no longer need it to bend or flex let it dry just a little in an open bag or between paper in an almost closed bag for one day now it is -
Leather soft –
now it is soft, but not bendable, still quite wet. This is the stage for attaching other clay pieces like handles or exterior decoration. It is a good stage to carve deeply. When working on the wheel this is when we foot. A wheel project can reach this stage if it is left in a locker or cupboard for one night with the door shut. In a firm slam project this is the stage when we join the slabs.
Leather Hard -
A project that is let to dry a little more – in a more open bag – is still dark gray but not at all soft or bendable. It is between dry and wet. This is a good time for carving or etching the clay. This is when we ‘finish’ the project. It is the last chance to foot a project or join another piece of clay. When joining clay to a leather hard project take care to keep the entire project in a bag afterwards and even add some wet clay to the bag to provide extra moisture.
Bone dry or Greenware
At this point the clay is dry – most all the water is evaporated out and it is not ‘cold’ to the touch. It has gone through the last of the physical changes and is ready for the bisque kiln. If you put it back in the water it would dissolve back into wet clay.
It is too dry to modify in anyway. It is very brittle. Beware clay that is part bone dry and part leather hard. This is a dangerous stage for cracking and breaking. Never foot it at this stage. (If the project is only partly dry sometimes you can bring it back to leather hard by putting it in a ziplock with wet clay – but this is a trick that does not always work….)
The first firing takes out all the water both physically and chemically bonded in the molecules of clay. IT is a chemical change. The first day the clay slowly heats up – this day is the ‘drying out’ day. The second day the temperature ‘ramps’ up to cone 04 close to 1,900degrees F. At this point the clay is ‘bisque ware’. It has gone through a chemical change. It appears light pink or white and it rings if hit with a pen. It will not change back to clay if put in a bucket of water. It has become like a brick.
The final step is putting on a liquid mix of powdered materials that make a glaze. These materials include silica, clay, alumina, a small amount of metal oxides for color and flux to make it melt at the temperature we are using. We fire at cone 5 which is over 2,000 degrees. The project that comes out is now ‘vitrified’ the clay turned to stone and covered with a glass glaze that is bonded to the surface of the project.
Your project is water proof - and if well made – without pits in the glaze and or other flaws that might trap food particles – can be used in the kitchen. They are microwave and dishwasher safe. There is no lead in the glazes.