What are ceramics?
To start with some basic definitions in order to fully understand this small article. This is just a very short explanation about ceramics, if you want more detailed information I would suggest to take a course, read books and learn.
Ceramics: pots and other articles made from clay hardened by heat.
Kiln: Special oven for firing ceramics
Pottery: pots, dishes, and other articles made of fired clay. All pots are ceramics, but not all ceramics are pots.
Clay: a natural material created by weathered rock. It is soft, malleable and will permanently harden if baked at high temperatures
Greenware: Unfired ceramics/pottery
Glaze: a thin layer of liquid which is put on a piece of pottery and becomes hard and shiny when the pottery is heated in a very hot oven
Types of clay: Earthenware, porcelain and stoneware
One of the differences between the three main types of clay are the temperatures at which they are fired: Earthenware is fired to a temperature around 1100°C whereas and porcelain and stoneware are fired to temperatures around 1250°C. Personally, I chose to work with stoneware.
The journey of clay into ceramics
First I model my clay into the shape I want it to be, for example a pot. I have to keep in mind that when the clay dries, it shrinks.
When my object is fully dry, it is called greenware and is ready to be baked a first time in my ceramics kiln at about 950°C. This first firing is called a bisque fire. This will transform my clay from greenware into an intermediate stage where I can glaze my product before the final glaze firing. After it has been fired a first time, there is no possibility to transform my object back into clay. The clay has permanently changed.
I patiently wait for my kiln to cool down.
When the objects, pots, ceramics come out of the kiln, they are all ready to take a little bath. Every piece is carefully wet sanded and washed to make sure it is dust free before glazing.
Then they are ready for some coats of glaze. I use commercial glazes, that are all foodsafe, without lead or toxic components that might end up in your food by transfer. This is very important! Safety and health come first!
After carefully glazing all the pieces, they are ready for their glaze firing. The pots will get hot! When they do, the glaze (made out of glass, chemical powders etc) will melt giving the pot a shiny or matte finish. A glaze firing typically takes up to 9h. When the kiln is finished, it will slowly cool down. Again, this is a great test for your patience. It is not recommended to open a kiln over 100°C, otherwise your glaze might crack.
After a good 15 hours cooling time, it's finally time to see the final product!
This last opening is always special. There are good surprises and sometimes bad ones. Clay is a material that "lives" and the outcome is sometimes different from the expectation.
Please note glaze is optional. It is totally possible to fire your clay/greenware directly at maximum heat and obtain a non glazed ceramic objet.
I hope you enjoyed this short explanation about ceramics! See you soon!