Can ceramics be fired twice?

You've completed your first bisque firing and are wondering what comes next. Can ceramics actually be fired twice, three times, or even more?

The short answer is yes. Ceramics are typically fired twice – and sometimes even three times or more. This isn't unnecessary effort, but rather based on solid chemical and technical reasons. In this article, we at Formwerk Berlin will explain why this is the case, what happens during each firing, and when a third or fourth firing truly makes sense.

If you're just starting out and are wondering how long your clay needs to dry before it can even go into the kiln, you'll find all the important information here: How long does clay need to dry before firing?

This article is written by Formwerk Berlin Pottery Supplies.

Why are ceramics fired multiple times?

To understand this, it helps to look at what happens to the clay during firing. When you put bone-dry clay into the kiln for the first time, it is solid but still porous and, chemically speaking, still clay. Only through heat do irreversible chemical reactions occur: crystalline water escapes, organic components burn away, and clay minerals begin to bond.

The result of this first firing is called bisque – a solid, permanently altered body that can no longer be dissolved in water. However, it is deliberately kept porous because it is intended to absorb glaze in the next step. And this glaze, in turn, requires its own firing to melt and bond with the bisque. Hence, at least two firings.

Overview: How many firings are possible?

Depending on the technique, glaze, and decoration, a ceramic piece can undergo one, two, three, or even more firings. Here's an overview:

Firing 1: The Bisque Firing – what exactly happens?

The bisque firing is the first firing a ceramic piece undergoes. It typically takes place at temperatures between 900 and 1000 °C. That sounds like a lot – and it is a lot. Several things happen simultaneously in this temperature range.

These pieces must be "bone dry" before firing to withstand the stress moments of the quartz inversion in the kiln.

Up to about 150 °C, any remaining free water escapes as steam – which is why bone-dry pieces still need to be heated slowly. Between 200 and 600 °C, organic components and impurities in the clay burn away; it can lightly smoke, and the kiln should be well-ventilated. From about 573 °C, quartz undergoes a crystal lattice transformation (quartz inversion) – a brief moment of stress for the material, where the heating rate should not be too fast. Between 600 and 900 °C, chemically bound crystalline water finally leaves the clay, and the clay minerals begin to sinter, i.e., bond together.

Important to know: This stress moment also applies on the way down! During cooling, the material goes through the quartz inversion again. If you open the kiln too early out of curiosity, you risk fine cracks in the bisque due to the cold shock. Patience is the most important ingredient here – leave the kiln closed until it is below 200 °C.

The result: a porous, durable bisque that no longer dissolves in water, feels good in the hand, and soaks up glaze like a sponge. This is precisely what makes it so valuable for the next step.

Important when loading: During bisque firing, pieces can touch and even be carefully placed inside each other – this saves space in the kiln. However, pieces that will not be glazed later should not be stacked inside each other, as different firing atmospheres can lead to local color differences.

Kiln efficiency: Since pieces in bisque firing do not yet have glaze, they can be stacked to save space, as seen here with these plates.

Firing 2: The Glaze Firing (or Glost Firing) – now it gets smooth

After bisque firing, the glaze is applied to the still porous bisque – by dipping, pouring, or brushing. The pores of the bisque absorb the watery glaze suspension (or, more commonly, liquid glaze) and ensure that an even layer adheres. This only works because the bisque is still porous – an over-bisqued piece (too high bisque firing temperature) will hardly absorb any glaze.

During the glaze firing, the glaze melts at temperatures between 1000 and 1280 °C – depending on the type of clay and glaze – into a smooth, glassy layer on the surface. At the same time, the clay body continues to densify. For earthenware, it becomes denser but not yet fully vitrified; for stoneware and porcelain, the body fully vitrifies during the glaze firing and becomes waterproof.

From dull blank to glossy unique piece: The glaze firing melts the glaze powders into a dense, colored layer and transforms the porous bisque into a finished, glazed ceramic.

The exact temperatures always depend on the specific clay body and the manufacturer's instructions for the glaze. Especially with porcelain and modern stoneware bodies, there are now variants that mature completely at significantly lower temperatures (from 1200 °C).

During the glaze firing, the pieces must not touch, as the molten glaze would otherwise stick together. Each piece needs a small gap all around. Furthermore, the bottom area must remain glaze-free or stand on a tripod – otherwise, the piece will stick to the kiln shelf during firing. Kiln shelves should be coated with kiln wash before glaze firing.

The hold time at the end of the glaze firing – typically 10 to 20 minutes at the target temperature – is important for the glaze to melt completely and evenly. Without a hold time, the glaze in the center of the kiln might look different from the edges.

What is single firing – and why isn't it always done this way?

There is also the option of combining bisque and glaze firing in a single firing process: the so-called single firing (more commonly: once-firing). Here, the glaze is applied directly to bone-dry, unfired clay, and everything is fired at once.

This sounds tempting – heating once instead of twice, less energy, less waiting time. And for experienced potters with certain clays and glazes, it works. But there are good reasons why the standard approach involves two firings:

1) First, the piece is very fragile in its unfired state. Even during glazing, the clay reabsorbs water and can warp or be damaged. 2) Second, in single firing, all crystalline water must escape through the glaze layer – which can cause bubbles, pinholes, or blistering, especially in thick-walled pieces or low-melting glazes. 3) Third, errors only become visible during single firing: a piece that explodes during bisque firing can, in the worst case, take other pieces in the kiln with it. If a bisqueware piece breaks, only clay fragments without glaze are created – no damage to adjacent pieces.

The left mug (single-fired) shows typical defects like pinholes despite the time savings, while the classically bisque-fired mug on the right has a convincing glaze surface. Image source: Digitalfire

If you still want to try the single-firing method, an adapted firing curve is recommended: a very slow heating rate up to 200 °C with a 30-minute hold, then slowly again up to 600 °C with another hold, before reaching the final temperature.

Firing 3: The Color Firing – for painting on finished glaze

Sometimes, the process isn't finished after the glaze firing. If you want to paint your fired ceramic with delicate patterns, detailed motifs, or specific colors that wouldn't withstand high firing temperatures, you'll use the overglaze technique.

Here, overglaze colors – also called muffle colors – are applied to the already fired and glazed surface. These colors consist of powdered metal oxides mixed with a flux. The flux lowers the melting temperature so that the so-called color firing can take place at just 750 to 850 °C.

At this temperature, the colors gently melt into the finished glaze and permanently bond with it. They become abrasion-resistant and waterproof. The overglaze technique has a centuries-old tradition: the famous Meissen porcelain manufactory developed the first overglaze colors for delicate decorative work in the early 18th century. Today, about 500 different overglaze colors are available.

The decisive advantage: Since the color firing takes place at a lower temperature, even sensitive color shades survive the firing unscathed – especially reds, which would burn out at high firing temperatures.

Can you re-fire glaze – and why would you do that?

Yes, it is generally possible to put already fired glaze back into the kiln. This is called a correction firing or repeated glaze firing. There are various situations in which this can be useful:

Correcting glaze flaws: If the glaze has unsightly spots, too thin areas, or an uneven flow after firing, you can apply another layer of glaze and fire it again. However, the result is not always predictable – sometimes it gets better, sometimes new irregularities appear.

Second glaze layer for depth: Some effect glazes only develop their full character through multiple layers and firings. This is not a flaw correction but a deliberate design choice.

Underfired colors: If glaze colors appear paler than desired after firing, a second firing can sometimes increase the intensity – but this depends heavily on the specific glaze.

Important to note: If you apply a new glaze layer over an already fired glaze, it will dry more slowly than on bisque – the smooth glaze surface no longer absorbs water. Some potters briefly warm the piece to 60 to 100 °C beforehand so that the glaze adheres better. Never fire higher than the last glaze firing, otherwise you risk the existing glaze flowing excessively again.

Bisque firing temperature higher than glaze firing – is that possible?

An interesting variation for advanced potters: firing the bisque higher than the subsequent glaze firing. This sounds unusual, but it has a practical reason. If bubbles, pinholes, or craters appear on the glaze during the normal two-firing process, it is often because gases from the clay body have to escape through the already melting glaze during the glaze firing.

If the bisque firing is fired higher – for example, to 1060 °C instead of the usual 950 °C – these gases are already driven out before the glaze firing. In the glaze firing, which is then just below that (e.g., 1040 °C), there is hardly anything left from the body that would need to pass through the glaze.

This method works well with modern liquid glazes and some clay bodies. However, it has two limitations: the body becomes denser and absorbs glaze less effectively, and it is not suitable for outdoor ceramics (frost resistance requires high glaze firing temperatures). Always check the firing temperature of the clay body used beforehand.

What happens to the clay with each additional firing?

An important principle: Each firing changes the clay further – and many of these changes are irreversible. Once clay has been fired, it is no longer clay in its original sense. It cannot be soaked and reshaped.

This has practical consequences: If a piece breaks during bisque firing, the shards are lost – they cannot be reused. An unfired piece, however, can be soaked and the clay reprocessed as long as it has not yet been in the kiln.

With each subsequent firing, the body compacts a little more. During glaze firing, most pores close due to sintering. If you want to correct or rework a piece, you should do so before glaze firing – after that, the possibilities are limited.

Can ceramic be fired too often?

Theoretically, yes. Every firing means thermal stress for the material. Frequent repeated heating and cooling can lead to fine cracks – especially if the glaze and the clay body have different coefficients of expansion. Furthermore, glaze can flow and run with each additional firing, especially if it was pushed to the limits of its firing temperature the first time.

 

As a rule of thumb: Third firings (decorating firing) are usually problem-free if fired at the correct, low temperature. Corrective glaze firing at the same or lower temperature is usually also unproblematic. However, multiple firings at high temperatures are not recommended and rarely yield predictable results.

What does this mean for beginners?

As a beginner, it is perfectly sufficient to follow the classic two-firing method: bisque firing, glazing, glaze firing. This is the most reliable way to achieve beautiful and durable results. Bisque fire at approximately 900 to 960 °C, glaze fire at the temperature specified for your clay and glaze – and with a programmable controller, this can be controlled very well.

Those who are buying their first kiln or wondering which model is suitable for beginners can find a comprehensive overview here: Formwerk Berlin – Kilns. Matching controllers that allow precise programming of heating ramps and holding times are available here: Controllers for Pyrotec kilns and Bentrup Controllers for Kittec kilns.

For those who want to start at home or in a small studio without a high-power connection, the Pyrotec Profitherm PY 75 H is a good choice.  

Frequently Asked Questions Briefly Answered

Conclusion

Firing ceramics twice – this is not effort for effort's sake, but follows a logical artisanal sequence. Bisque firing prepares the body: firm, porous, stable. Glaze firing completes the piece: dense, smooth, water-repellent. If you then want to work with overglaze colors, you add a third firing at a lower temperature.

As a beginner, you will quickly notice that this two-part division has real advantages: errors become visible early, glazing is more enjoyable on a firm body, and the result is more reliable than with the single-firing method. Over time, you will learn to control the firings precisely – and a good kiln with a programmable controller will be your most reliable helper.

A selection of suitable kilns and accessories can be found here: Formwerk Berlin – Kilns.

PS: In 2026, you will receive 5% discount on all kilns and kiln furniture in our store with the code WELCOME5. Simply enter it at checkout and the discount will be applied directly to the purchase price.

The Formwerk Berlin Team wishes you much joy in glazing and good firings!