When it comes to clay firings, there are two main categories you need to be aware of: electric kiln firings and gas kiln firings. Though the two firing methods may initially appear quite similar, their processes are actually quite different and understanding the distinctions will help you determine which is the best option for your project. This article will provide a comprehensive overview of both types of clay firings, offering key advice and tips on how to get the best results out of your work.
Types of Clay Firings
Clay firings involve heating the clay pieces to high temperatures in either an electric kiln or a gas kiln. The main difference between electric and gas kilns lies in the source of heat used to fire the clay pieces. Electric kilns use an electrical source to generate heat, while gas kilns use burning gas. Both types of firing can achieve excellent results, however, their processes vary greatly in terms of time, cost, and complexity.
Electric Kiln Firing
Electric kiln firings are the most popular firing method for pottery, as they are relatively straightforward and require minimal set up. Electric kilns are typically heated to temperatures between 1000°C and 1400°C (1832°F-2552°F). The process starts when the kiln is switched on and pre-programmed with specific firing temperatures and times. Once the kiln is fired up and reaches the desired temperature, the clay pieces are placed in the kiln where they are rapidly heated until reaching their maximum temperature. The pieces are then slowly cooled down in a process known as annealing.
Gas Kiln Firing
Gas kiln firings require more knowledge and skill than electric firings, as the heat is generated from combustible gas. Gas kilns can reach significantly higher temperatures than electric kilns, typically ranging from 1600°C-1800°C (2912°F-3272°F); however, some of the newer models can reach temperatures upwards of 2000°C (3632°F). As a result, the process of firing clay pieces with a gas kiln requires caution and precision, as it is much easier to damage the pieces when using this type of firing. Also, it should be noted that there are special safety protocols that must be adhered to when using a gas kiln.
Raku Firing
Raku firing is a popular form of firing clay pieces that originated in Japan. As opposed to standard firing methods (such as electric or gas kilns), Raku firing involves quickly heating the clay pieces to temperatures below 1000°C (1832°F) and then rapidly cooling them by exposing them to air. This process results in unique and beautiful glazes, as well as textured surfaces that are unlike those achieved through other firing methods. Due to the unpredictability of Raku firing, it is recommended for experienced potters only.
High Temperature Firing
High temperature firings involve heating up the clay pieces to temperatures above 1600°C (2912°F). This type of firing is generally used to fire stoneware pieces or other items that require a very strong material with low porosity. The main advantage of high temperature firings is that they produce a much stronger product that can withstand greater stress. However, they can be difficult to perform correctly and require special equipment and materials.
Low Temperature Firing
Low temperature firings involve heating up the clay pieces to temperatures below 1100°C (2012°F). The advantage of low temperature firings is that they require less energy and less complicated equipment than high temperature firings. Low temperature fired pieces tend to be softer and more porous than those fired at higher temperatures, which may make them more suitable for some projects; however, they can be more susceptible to breakage or cracking.
Pit Firing
Pit firing is an ancient and traditional method of firing clay pieces in which the entire process takes place in a large pit that has been filled with combustible material. In this type of firing, a variety of natural materials such as wood, leaves, and sawdust can be used as fuel to generate heat. Pit firings can produce unique glazes and surface textures, however, they can be time consuming and require considerable preparation work such as digging the pit and gathering fuel.
Wood Firing
Wood firing uses wood as its main source of fuel to heat the clay pieces. Though it’s similar to pit firing in terms of setup and process, wood firings tend to fire up much faster than pit firings since they rely on more natural combustible materials. As with pit firings, wood firings also produce unique glazes and surface textures, however they do require more maintenance as they need to be refueled constantly.
Salt Firing
Salt firing is another type of clay firing that uses sodium chloride (table salt) as its main source of fuel. Salt fires generate very high temperatures (between 1100°C-1300°C or 2012°F-2372°F) and produce unique surface textures and coloration. Salt firing is a complex process that requires a good understanding of ceramic chemistry in order to produce desirable results.
Saggar Firing
Saggar firing is a specialized type of kiln firing technique in which the clay pieces are placed in an enclosed container called a saggar (or sagger) along with various combustible materials such as sawdust, leaves, cardboard, or newspaper. During the firing process, the combustible materials create both smoke and heat that form unique glazes and interesting patterns on the pieces.
Slab Rollers and Extruders
Slab rollers and extruders are essential tools for anyone who wants to create ceramic pieces from raw clay. Slab rollers are used to flatten out the clay into a desired thickness while extruders are used to force or “extrude” the clay through a die or shape into intricate designs. Both tools are invaluable when it comes to creating pottery and other ceramic pieces.
Preparing Clay for Firing
Before any clay piece can be fired, it must first be prepared by drying and adding texture or glaze to it. Thoroughly drying out your clay pieces is essential in order to achieve consistent results during the firing process. Adding texture or glaze can help enhance the look and feel of the piece while also providing protection from external elements. Once the clay piece is completely dry and finished with texture or glaze, it is ready for firing.
Caring for Fired Clay Pieces
Once your clay pieces have been fired properly, it’s important to ensure that you properly care for them in order to maintain their beauty and durability. The first step is to properly clean them with warm water and soap to remove any residue from the kiln or glazes used during the firing process. After cleaning, clay pieces can then be coated with a sealant such as wax or oil for additional protection. Additionally, storing your fired pieces in a cool, dry environment will help ensure their longevity.
Understanding how different types of clay firings work will help you in your pursuit of creating beautiful pottery or ceramic pieces. From electric kiln firings to pit firings and everything in between, there are numerous options available when it comes to firing clay pieces. Hopefully this article provided you with a comprehensive overview of both types of clay firings and offered key advice on how you can get the best results out of your work.
