Kiln firing is an art that takes time and skills attained over the years to achieve perfection. If you are a beginner, kiln firing might not be suited for your pottery projects. You might end up doing more damage in the process. So, what can you do to complete your project? Well, the best replacement for pottery kiln firing is oven firing.
However, as easy as oven firing might sound, the truth is far from it. Even oven baking your pottery item would require you to follow different rules and regulations from start to end. When starting your journey as a pottery artist, you obviously wouldn’t want to spend a lot on something as massive and complicated as a kiln.
So, before we get to the mistakes that one can make during a process as complicated as pottery firing, let us learn why you should fire it at all!
Why should you fire your pottery pieces?
Any potter wants permanency for their masterpieces. No one would want the artwork to get ruined after hours of hard work. So, what is the best way out? It is to fire your pottery pieces. Whether you fire it with the help of a powerful kiln or through your regular home use oven, the result is mostly the same for both.
However, the process for firing in the kiln and firing in the oven is pretty different. So, let us take a glance at some of the benefits brought in by pottery pieces that have been fired perfectly.
- Post firing, your clay pottery tends to become sturdy and hard. Make sure you fire the clay only after you have completed shaping the project. Else, once the piece hardens, you cannot go back and make changes. Doing this also ensures that the clay doesn’t melt away once it is exposed to moisture. In simple words, your clay would turn waterproof post-firing. However, keep in mind that this isn’t to say that it becomes completely waterproof. A small amount of moisture would surely seep in with time. In short, one can say that it becomes resistant to water.
- Firing makes the clay hard & durable. This means it won’t go back to its original shape and maintain the texture and design that you have added. Plus, even if you touch it or hold it tight, the pottery piece won’t change in design or mush together.
- Firing, especially when done after glazing the surface, gives it a beautiful texture so that there is no moisture or rough feeling. Plus, you can always sand it down to ensure that the surface feels smooth without having to ruin the overall design.
- When you fire your piece after glazing, it helps flux & fuses all the chemicals that might be present in your pottery glaze. This makes your pottery piece food safe. It can be used to store food or use as utensils for daily use.
- Firing after the glazing process ensures that your glaze sticks to the surface of the pottery pieces properly. Regardless of how it is being used, the glaze won’t come off or chip.
- Lastly, firing in the right way ensures that the mud pottery piece is converted into the ceramic form for longevity.
Now, you might ask why there is a need to ensure safety and careful processing while you fire your pottery piece. You must be careful because firing your pottery with the wrong processes in place might induce issues such as breaking, cracking, & even explosion of the pottery work. This isn’t simply disappointing but a risky thing as well.
This is why it is important to understand the factors that you have to understand before firing your pottery piece in an oven.
Here are the mistakes you might commit when firing the pottery in an oven.
1-Failing to Understand the Clay Type:
When you fire the clay, you must understand the type you are using to make a project. If your clay body isn’t compatible with the oven firing temperature, it could lead to malfunctioning. If your temperature range fails to match with your clay type, this could lead to problems such as sagging, shrinking, cracking, or warping of your pottery piece.
This is why you need to have a proper grasp over the clay type & a suitable temperature for firing. Now, let us decode each clay type depending on how it should be fired. If you are using an earthenware clay body, your project will do better if you set it at a lower firing temperature. Remember, it could pack in a good amount of plastic along with several mineral compounds. This mixture helps it attain an optimum temperature rather quickly, which leads to a quick-firing experience.
However, you must keep in mind that the temperature stays at a uniform level and doesn’t fluctuate a lot. If this happens, it could lead to unfortunate cracking of your pottery piece or even lead to burning of the clay. On the other hand, if you plan on using the stoneware clay, it is important that you start with mid-range/high-range firing in order to reach maturity. Plus, a firing range that is set high would also be applicable for the pottery pieces made from porcelain clay. Most of the earthenware clay items are fired in temperatures ranging between 998 oC to 1142 oC.
Next, you can also use ball clays in order to create your pottery piece. These clay pieces also require you to use a high-temperature oven that can go as high as possible to about 1285 oC. However, you need to keep in mind that a home oven might not reach such a high temperature. So, you could opt for a commercial oven that is designed for high-temperature firing.
2-Not Drying Your Clay Piece before Firing:
Yes, we put a pottery piece inside an oven or kiln to dry out all the moisture and make it hard. However, before you put the pottery piece inside, you need to dry it out as naturally as possible. Putting a wet clay project within the oven can lead to unfortunate incidents such as bursting or explosion within. This would break your hard work into 100s of pieces while exposing you to fatal accidents as well. So, remember not to put the moist or wet pot within an oven or kiln.
While normal clay cannot be dried out completely simply with the air-dry process, you can try to let out as much moisture as possible. When you keep your pottery piece out in the sun or even at room temperature, it would attain a dry leather texture. This is too dry in status to meltdown completely. However, it isn’t hard enough to be considered durable. Changes can be made at this stage, too, with the use of a bit of water. With normal clay, you need to start with a lower temperature and then go ahead and increase the same to a suitable temperature for proper firing.
Put your piece inside the oven and start your firing with a lower temperature as suited to your clay type. Slowly increase it to the desired temperature. Doing this would help maintain an easy transition of your pottery piece from a moisture-loaded one to a complete bone-dry variant. If you place your pottery piece in a pre-heated oven, it could lead to faster temperature change. This, in turn, would cause the pottery to dry out too fast and lead to chipping and breaking at different parts.
If you plan to glaze your pottery piece, it is important to do so once the pottery piece has dried out naturally. Adding glaze to your wet clay would lead to chipping, and the glaze would come off easily once the pottery piece has dried out. You can check if the piece is completely dry by touching the surface. In case it does feel a tad cold when you touch, you must allow it a chance to sit for some time more. Once you feel that the piece isn’t cold, you can be assured that it is completely air-dried. After this, you can glaze your pottery piece.
However, you cannot place the piece directly within your oven post-glazing. You need to let the glaze dry as well. Only after you do this can you transfer your piece into the oven for firing purposes. The rules for kiln firing would be a bit different than this. However, let us leave that to you later when we master the art of firing the clay in an oven.
Whether you use air-dry clay, earthenware clay, stoneware clay, or any other variant, clay is known to dry out, and this drying leads to shrinking. As it is, the oven is smaller as compared to a kiln. So, you cannot create a massive pottery piece with the help of an oven. If you plan to bisque fire or glaze fire in an oven, be assured that it isn’t going to work as well as you would expect with a kiln. However, the fact is that you need to size properly in order to achieve the best results with oven firing.
If you plan to create a massive project, you can fire in parts and later join them together with the help of a pottery glue or slip. A slip is a mixture of clay and water where it is watered down to a glue-like consistency. This slip is then pasted onto the parts to join them together. After the slip has dried out, your pieces would be as good as they come.
On the other hand, if you plan to use a base for your pottery project, you need to ensure that the clay body is larger than the base. After you fire the piece, you might see that the pottery piece would shrink down a bit. If you don’t size your pottery piece properly, the base layer won’t shrink down. However, the upper layer would shrink on top of it and cause the project to break down, and the base would show.
Apart from this, you need to remember that the clay dries out depending on the thickness and layers involved. If your project has multiple layers, you need to increase the firing time for the same. You must also ensure that the thickness of the clay must be optimum. The thickness must not be more than 1/4 thof an inch to ensure that the firing process is smooth and glitch-free. Apart from this, you also need to ensure that the glaze thickness must not be more than what is necessary. Glazing thickness failure can lead to issues such as dots or pin holing in the clay surface. It could also be a result of uncontrolled firing temperature.
Safety is Important When Firing Pottery in an Oven
While oven firing might not be as risky as kiln firing, it could still be a risky affair, especially if you fail to follow the instructions properly. Always make use of safety gloves designed for pottery firing purposes to ensure that you do not burn off your hands when taking out the pottery piece from the oven. You can make use of the Rapicca Leather Forge Fire-Resistant Oven Mitts. This 16-inch extra-long glove pair comes with genuine cowhide material with split leather & air-isolated aluminum to ensure your hands don’t burn out.
Apart from this, it is better to use protective glasses for your eyes, in case there is an unfortunate accident. Remember to let the pottery piece cool down after you are done firing. Do not take it out instantly. Doing this not only exposes you to burns but also leads to cracking in the pottery piece due to sudden temperature drop.
So, the next time you plan on firing your pottery piece with an oven, make sure you stay attentive and conscious enough. Always ensure that you stay at a safe enough distance when working with oven firing. Wearing fire-resistant shoes and clothes also serve as an additional safety measure for your firing experience.
Originally published at https://spinningpots.com on August 4, 2021.