It’s interesting to see how much the glazing, alchemy, and human life relate to each other. Bernard Leach, author of A Potter’s Book, helps us understand glazes by relating them to the body. He says most glazes have three main parts -- the blood, bone, and flesh. Here is how they work:

            1.) Fluxing agent  or “life blood of the glaze” – causes the glaze materials to melt and flow together in the kiln firing.

            2.) Refractory or “bone of the glaze” - resists heat and melting, providing structure and strength to the glaze body.

            3.) Glass Former or “flesh of the glaze” - creates complexity, depth and unique qualities.

      The early alchemists fused their chemical efforts with the body. Calling their experiments the Magnum Opus or “Great Work,” these men searched tirelessly for the right chemical concoctions that would enrich life or prevent death. In some ways, full-time potters do the same through glaze chemistry. They are constantly searching for that perfect potion that will immortalize a clay body and turn sand, water, and ash into gold.

     The earliest record of pottery dates back to the Late Paleolithic period in central and western Europe, where fired and unfired clay figurines were created as a form of artistic expression. As early as 30,000 years ago, at a site known as Dolni Vestonice in the Czech Republic, figurines made of clay mixed with crushed mammoth bone were found. Evidence of pottery has also been found at an archeological site known as Odai Yamamoto, in Japan, where fragments from one of the vessels have been dated to about 16,500-14,920 years ago.

     Open firing techniques were used to produce the earliest pottery. Through this method, temperatures could range from 600-900 degrees Celsius, which are relatively low temperatures. Firing pottery in a kiln produces much hotter temperature. Enclosing the pottery inside a chamber results in key advantages: the temperatures that can be achieved are higher, last longer, and the heat can be controlled more efficiently. The simplest forms of kilns are pit kilns, which is a pit fire installation where the fuel is placed at the bottom, followed by the pottery, and more fuel in the upper layer. Another type of kiln is an updraft kiln, which is usually a cylindrical construction divided into two compartments: the lower compartment is where the fuel is placed, while the pottery is placed in the upper compartment. This allows the heat to rise and the pottery is fired at a temperature level normally ranging from 1,000 to 1,200 degrees Celsius. In ancient China, firing techniques allowed temperatures of about 1300-1400 degrees Celsius and even higher in some cases.

     At these temperatures, the mineral components of clay melt, resulting in a thin, translucent, white vitrified type of ceramic that is known as porcelain. By analysing the chemical composition of pottery fragments, it is possible to determine at what temperature the pottery was exposed, and therefore we can understand the level of technological sophistication of a society, at least in terms of their firing capabilities.         - http://ancient.eu