Minerals have always been an important material used in the firing process by potters. A potters goal is to control the thermal behavior of their materials to create pieces with specific characteristics. Clay and glaze are composed of various raw mineral materials, and the firing process has to be adjusted to these ingredients to achieve desired results.
The first step of firing minerals is to prepare the mineral raw material. This includes crushing, grinding, and tempering. Depending on the desired result, the temperature and setting can vary. This can range from cooling and breaking down a high temperature-resistant material to heating it to soften and make a more flexible material. After the material has been prepared, it is time to begin the firing process.
The firing process begins with preheating and continues through the cycle beyond the point of maturation. Preheating is important as it reduces the moisture in the material, which will have a bearing on the end result. The temperature of the preheat can range from room temperature to 500°F depending on the mineral being fired. The heat cycle of the firing is carefully adjusted to bring out the best qualities of the mineral material.
During the firing process, minerals create reactions and penetrate each other to create a chemical reaction. These reactions change the chemical makeup of the materials and can give the piece specific attributes and characteristics. The type and rate of reaction can be adjusted through adjusting the temperature, humidity, air flow, and atmosphere during firing.
The firing cycle is complete when the temperature is reduced to room temperature. The firing process has two stages: oxidation and reduction. Oxidation is when oxygen is added to the firing atmosphere. This chemical reaction helps to drive out carbon dioxide. Reduction is when a reducing atmosphere is created by introducing chemical elements, such as coke, which absorb oxygen for a more stable chemical reaction.
Firing minerals requires knowledge and expertise along with an understanding of the process and material. A good firing can enhance the texture and color of the piece, while a bad firing can have a negative effect. For the best outcome, it is important to have the right equipment, use the right techniques, and understand the raw material. With the right preparation and knowledge, firing minerals can be rewarding and enjoyable.
