The Firing Process

The firing process is the process in which high temperatures are used to turn raw clay into ceramic. Firing is an expansive universe full of different techniques and methods. I’ll be speaking about my process and what’s work for me.

Following a fresh throw, I’ll leave the piece out to dry, carefully monitoring it to track its moisture content. At this point, I consider the piece greenware. Greenware is clay that hasn’t been fired yet but is in the process of air drying. This stage has subcategories describing how much moisture is still in the piece; this includes leather-hard clay and bone-dry clay. Leather-hard refers to when a piece is, well, leathery in feel. It can be handled without putting its main form in jeopardy but can still be slightly altered. This is a great time for a trim! When finished altering a piece, I leave the piece to air dry as much as possible – sometimes for as long as a week depending on the weather. Once as dry as possible, the piece is now bone-dry and ready for it’s first firing.

The first fire is called the bisque fire. During this fire, bone-dry pieces are relieved of all chemically bonded moisture. For stoneware clay, this is typically accomplished when the kiln reaches a temperature of about 1830F/1000C. Once complete, the pieces are now a bit stronger, cannot be altered, and are extremely porous – perfect for sucking up glazes!

Once bisque has been meticulously decorated with glazes, (glaze: a mixture of water and a complex blend of minerals that gives finished pottery it’s glassy coating), it’s time for the final fire. During the glaze fire, glaze ingredients melt and permanently adhere to the piece’s now vitrified body. Stoneware typically reaches this stage after being exposed to an astounding 2200F/1200C! Once cooled, the finished pieces can be held, used, and adored. As a potter, the anticipation of opening a glaze kiln is much like a five-year-old’s anticipation for Christmas morning!