Glazing and firing are two essential steps when making any pottery. But if you’re new to Pottery making, you’ll find yourself wondering what comes first and what process you should follow.
Glazing Pottery is mainly done after the first firing. This first round of firing is called bisque firing and changes the clay permanently making it much harder but still porous enough to absorb the glazes. You can then decorate the bisqueware by either applying underglazes, glazes, or both after which you’ll need to fire again. You can also choose to fire the pottery only once.
It all sounds complicated, but it really isn’t. This article gets into all the details you need to know about firing your pottery, the right procedure for doing so, and the merits of single and double firings.
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The processes of firing and glazing
Before we get into all the details of these essential processes, we must mention that firing transforms the pottery from clay to ceramics. Therefore, whether you choose to do it only once or twice (some potters fire their pots more than twice), the most important bit is that you don’t skip this step when making pottery.
Once you’ve shaped your clay or taken it off the wheel, you have Greenware at this point. Greenware has three stages and is the most fragile in this state. You need to be careful when handling it. In the first stage, greenware is moist and malleable (workable). You can mold a spout, make waves around the rim, or apply slip.
You’ll then have to leave the greenware to dry until the second stage called leather hard. At this point, you can add any additional clay pieces you want. It’s still a bit damp, but you can comfortably handle the piece without changing its form. You can do any trimming, carve any details into place, apply underglaze or slip as you deem fit before letting it dry to the final bone dry state.
Once your Pottery is bone dry, it’s ready for the first round of firing.
This refers to the first round of firing and aims to convert the greenware into a hard but porous material to absorb glaze. Additionally, bisque firing burns out organic material in the clay. Once this first round of firing is complete, the product you’ll have is bisqueware, and it will be durable and porous enough to handle the glazing.
When firing your pottery, be aware of the temperature you fire to. Clays become bisqueware at certain temperatures. If you go too high, your pottery may not be porous enough to bond properly to the glaze.
Pyrometric cones also know as Witness cones come in handy when determining the right firing temperatures for your Kiln. This unit of measurement accounts for both time and temperature, to ensure that you get the temperatures right.
For bisque firing, the right temperature is such that the bisqueware is strong enough yet porous enough to hold the glaze. Therefore, the most suitable temperature for bisque firing is 1828 °F (998 °C) Cone 06 to 1945 °F (1063 °C) Cone 04. Once this step is complete, you can move on to glazing.
Glazing and glaze firing
Decorating your Pottery is where more fun lies. Glazes come in a variety of colors and ways to create your own masterpiece.
To apply the glaze to the bisqueware You can use a Brush, Sponge, Spray Gun, Pour, or Dip the entire piece into a glaze bath. Also, check out 9 Pottery Glazing Techniques to get more cool glazing ideas.
When you’re satisfied with the glazing result, leave the piece to dry before putting it into the kiln for the glaze firing. A golden rule is; Kilns hate moisture.
Glaze firing ensures that the glaze reaches the optimal melting point. Just like the bisque firing, ensure you get the temperature right to prevent the glaze from crawling.
Helpful tips for successful glaze firing:
- Ensure your ceramics remain clean after bisque firing. It would help if you also handled the pieces using disposable or rubber gloves to avoid creating resist spots using lotions and oils from your hands.
- Before you begin glazing, ensure you remove any rough spots you may have missed before bisque firing. Wet sandpaper works well.
- Mix and strain your glazes well before applying to your pottery.
- Apply your glaze whichever way you please until the glaze is as thick as a T-Shirt.
- Ensure your glaze is completely dry before placing the Pottery into the kiln for the glaze firing. If the pottery is still wet, you risk ruining it or even having it explode in the kiln.
For more tips on glazing read 27 Glazing Tips to get the best results from the beautiful pottery you spent so much time creating.
Can you fire pottery once?
Although most potters prefer firing their pottery at least twice, it is entirely possible to skip this process and use single firing. In this case, glazing is done on the surface of the third stage of greenware (Bone Dry). Potters that mostly use this method are pros that make their own glazes to be compatible for a single fire. It’s essential to note that not all glazes can work with a single firing. Most commercial glazes are designed for a bisque fire first. With a single fire the organic material did not burn off the clay yet, leaving room for error when firing.
The single firing technique uses Glazes that have a higher clay content. You’ll need to experiment to find the glaze recipe that works best for you.
Single firing presents a challenge in that it’s much easier for you to make a mistake. You’re more likely to encounter problems such as crawling and pinholing during the glazing process. However, some potters have mastered this art. It is possible to achieve excellent ceramic decoration even when using a single firing. Which is great because you less energy and it’s more cost efficient to fire once.
Benefits of double firing
So, what benefits does double firing present, and why should you opt for it?
- It ensures carbonaceous compounds are burned in the first firing so that they don’t affect the glazes, which ensures a better final result.
- It becomes easier to apply glazes after the bisque firing since the ceramic doesn’t risk coming apart or absorb too much of the glaze.
- You can easily correct a mistake you made while glazing.
- It is a better choice for potters who prefer decorative techniques like ‘glaze removal.’ For example, you can wipe off the high spots of a textured glaze.
Benefits of single firing
Although single firing presents a challenge when decorating, it does offer several benefits as well.
- It is less tedious since the process is more straightforward and will consume less time.
- Unlike double firing, you’ll only need to fire up your kiln once. Therefore, you end up using less power to decorate your pottery.
- When using underglaze, you don’t risk having the decorative pattern change after firing. The underglaze remains the same after firing.
You can glaze your pottery before, or after firing, depending on the technique you’re going for. Single firing consumes less time and power but needs a bit of expertise.
If you’re just getting started with pottery decorating, I recommend using the double firing method. Sure, it will take up more of your time and energy. However, it presents a more straightforward method of decorating your pieces and makes it easier for you to correct any glazing mistakes.