Why do you fire pottery

And loosely cover the whole piece with a bag, to stop draughts from drying out one area faster than another. Once your clay feels dry, you can put it in the kiln on a low heat for a while. This is called candling. Even though your pottery might feel bone dry, it may have moisture nestled in the deeper layers of clay. Some potters will put their pots in the kiln overnight at a low temperature. A low temperature at this stage is anything below boiling point. If you are candling overnight, the kiln is often set to around at a very low temperature, such as F 50C.

During the candling process, the lid of the kiln is propped open an inch or so with a kiln brick. This allows any moisture to evaporate out of the kiln.

For the same reason, the peepholes, also known as spyholes, on the side of the kiln are left open. Pre-heating your kiln involves setting the kiln at a low temperature for a few hours. For example, you might set your kiln to heat up to or F C for a couple of hours.

These temperatures are below boiling point, but they are hot enough to ensure that your pottery is completely dry. If the walls of your pottery are thick or uneven, it might be a good idea to pre-heat for longer. For example, pottery teachers in school will often pre-heat the kiln for about 4 hours. This is because student pottery is often a bit chunkier and needs more time to dry completely. Once the pottery is bone dry, it is normally fired two times.

The first firing in the kiln is called the bisque fire. This is sometimes called biscuit firing. When a kiln is firing, the temperature in the internal chamber rises. Typically, a bisque firing will reach around F C. I will say more about bisque firing temperatures later. Exactly how the kiln heats up depends upon the type of kiln you are using.

The majority of kilns are electric and are heated by electrical elements that sit in grooves along the wall of the kiln. But there are other types of kiln too, like gas kilns or wood-fired kilns. As the temperature in the kiln goes up, the clay undergoes a lot of significant chemical and physical changes.

Here are some of the changes that occur at different points in the bisque firing process:. So, at the end of the bisque fire, a piece of pottery will have undergone some significant changes. Once clay has been bisque fired, it has become ceramic. Because of the changes, it undergoes during firing, bisque pottery is hard but porous. During bisque firing, clay starts a process of becoming mature.

Clay is said to be mature when it is as dense and as hard as it can be. Some types of clay are able to become much denser and harder than others. The three most common types of clay that potters use are earthenware, stoneware, and porcelain. Stoneware clay and porcelain are capable of becoming harder and denser than earthenware. By contrast, stoneware and porcelain will continue to harden and densify in later firings. So, earthenware is more or less mature after a bisque fire. Whereas stoneware and porcelain are semi-mature and still have a way to go before they are mature.

However, regardless of the type of clay you are using, bisque pottery has some things in common. Usually, potters will bisque fire their clay to a target temperature in the range of F C. Pottery is normally bisque fired in this temperature range regardless of what type of clay is being used. By adjusting the bisque firing temperature a bit, potters can change the properties of the bisque pottery a little.

Pottery glaze is made up of ceramic materials suspended in water to form a liquid. You apply liquid glaze to bisque ware and then it goes into a glaze firing. Glaze firing is the last of the stages of firing clay. There are two main purposes of glazing pottery. The first is decorative. Glazing can give potter a range of colors, textures, and finishes.

Ceramic Glazing Techniques. Wheel Throwing Techniques. Search the Daily. In This Section. Firing clay is necessary to create durable wares and the more you know about the ceramic firing process, the more control and success you will have with your pots. Linda explains the physical changes that happen when firing clay and all of the key points in the ceramic firing process that could impact your results, such as quartz inversion and dehydroxylation.

If those words are new to you, or if you need a refresher course, read on! Firing Clay Explained Clay goes through several physical changes when fired. Topics: Electric Kiln Firing. Related Content. Would you prefer to share this page with others by linking to it? Click on the HTML link code below. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.

First Name optional. I am at least 16 years of age. I have read and accept the privacy policy. I understand that you will use my information to send me a newsletter. Lovely messages sent from visitors like you: Oh my goodness!

Thank you so much.