The process of firing clay
Firing is probably the most important part of pottery: it transforms clay from its soft and humble shape into something strong and mature, which is what we call ceramic. Vases, pots and other pieces of pottery made it through thousands of years simply because clay met fire.
What is firing?
Firing is the process of taking clay to very high temperatures to make it strong and, what we call "durable", which is when they have reached their optimal level of melting. The temperature needed to make this transformation is very high: your kitchen oven will not be enough to fire your pottery, as it does not get as high as 1000 C that you need for firing clay.
The melt happens on molecular level and the whole process is divided into two types of firing: bisque firing and glaze firing.
This is probably the least creative side of pottery, but I'm afraid it can't be avoided! With bisque firing, we refer to the process of shaped dry clay, or the so-called greenware, going into the kiln at high temperatures. This process vitrifies the pottery (meaning it gives it a glass-like look and feel), and this is the moment you can proceed to glaze your piece.
A couple of important things you have to be aware of: your pottery must be bone-dry in order to be bisque fired, and most importantly it is very delicate, so it needs to be handled very carefully and loaded in the kiln with the most care.
Another key factor is that low rise temperature is very important, this is because the bisque firing process takes out the last water in the pottery and if the temperature rises too quickly, the water will become steam and will make your pottery burst.
By the time the kiln has reached the desired temperature, the pottery will be completely dehydrated and changed forever: it will now be less fragile and much easier to handle. The kiln will have to cool off slowly, in order to avoid the pottery to crack due to thermal shock.
After you have decorated and glazed your pottery, it's now time to fire it again. Glazes make pottery even stronger and durable, besides colorful and beautiful!
Glaze is nothing more than a coating or layer applied to bisqueware to color and decorate it, but most importantly make it waterproof. Usually, two or three layers of glaze will be needed, but it really is up to you and what kind of look you want to give to your piece of pottery.
When you are bisque firing your pottery, you can stack them in the kiln, but not with glazed pottery: this is because the glaze will melt and if it touches another surface, by the time the kiln has cooled down, it will stick to it! (you do not want that to happen!).
The process of firing for the kiln is the same as per bisque firing: it will slowly reach its highest temperature and then it will slowly cool down. Glaze firing will remarkably change the glaze and clay, and will give the final touch to your pottery.