Bisque firing: What is it? Duration, temperature & costs

You have finished throwing or building your first piece, it has dried – and now what? Before you can glaze or fire it for good, most ceramics need a first, important step: the bisque firing. 

Here at the pottery supplier Formwerk Berlin we get questions about bisque firing almost every day, especially from beginners who are just setting up their first kiln. In this post we answer the five most common ones: What does bisque firing actually mean, how long does it take, what does it cost, can you stack pieces, and what do you need to watch out for?

Have fun, the Formwerk Team!

What Does Bisque Firing Mean? A Quick Explanation

Bisque firing is the first of usually two firings in ceramics. It takes place at comparatively low temperatures – typically between 900 and 1,000 °C – and turns the dried but still fragile clay into a firm yet porous body. This porosity is crucial: it makes the piece absorbent for the glaze that comes later.

Fresh from the kiln, before glazing: bisqueware is sturdy enough to handle but still absorbent for the next step.

A lot happens chemically during a bisque firing: residual moisture evaporates, chemically bound water is released from the clay minerals, organic components burn off, and the clay begins to sinter, meaning it lightly fuses together. After this firing, you can safely pick up your piece, glaze it with water-based glaze and prepare another firing without it breaking or dissolving.

In practice you will come across several terms for the same process: bisque firing (sometimes also spelled “biscuit firing”), raw firing, red-heat firing or pre-firing. They all mean the same thing. In this article we stick with the term bisque firing, which is the most common name in English.

How Long Does a Bisque Firing Take?

The direct answer: a complete bisque firing takes about 20 to 36 hours from switching on to safely opening the kiln. This surprises many beginners – they only count the heating phase and forget the cooling, which often takes longer than the heating itself.

In detail, a bisque firing is divided into three phases:

• Heating phase: 8–12 hours. The kiln is brought up slowly and in a controlled way. The first 600 °C are especially critical. More on that in a moment.
  
  
• Hold phase: 15–30 minutes. At the final temperature (usually 950 °C), the temperature is held briefly so that the heat distributes evenly in the kiln and all pieces are truly fired through.
  
  
• Cooling phase: 12–24 hours. This is where your patience is tested most. Do not open the kiln early to speed up cooling, or stress cracks may occur. Only below 250 °C can you crack the door open slightly, and ideally the kiln should only be opened fully below 100 °C.

The most critical zone in a bisque firing lies between 100 °C and 600 °C. In this range, the remaining physical and chemical water evaporates from the clay. If you heat too fast here, the water cannot escape and the piece can literally burst. A good rule of thumb for this phase: no more than 80–100 °C per hour. From 600 °C, the kiln can then heat up faster, often at 150–200 °C per hour.

Programmable kiln controllers make this controlled heating much easier. You enter the firing schedule once and the controller sticks to it. Manual controllers work too, but they require you to readjust regularly – no fun, especially on your first firing. If you don't know yet how long your own clay needs to dry before firing, you'll find the answer in our article How many days should clay dry before firing?

For the vast majority of kilns from reputable manufacturers such as Pyrotec or Kittec, a bisque firing is technically the easiest firing of all – even a small kiln handles the low final temperature of around 950 °C on a normal Schuko socket without any problem. Pictured here: the ST 52 H by Pyrotec.

How Much Does a Bisque Firing Cost?

The good news first: bisque firing is one of the cheaper firings. Because the final temperature of about 950 °C is much lower than for a glaze firing, and the kiln can hold the temperature in the final phase with relatively little power, the electricity costs stay manageable.

Concrete guidelines at an average electricity price of 37.3 cents per kWh (BDEW, new customer tariffs, as of October 2026):

• Small hobby kiln (230V, approx. 70–80 L, 2.5–3.6 kW): about €3–4.80 per bisque firing
• Medium studio kiln (400V, approx. 130–150 L, 9 kW): about €7–11 per bisque firing
• Large studio kiln (400V, approx. 200 L+, 12 kW): about €12–18 per bisque firing

These figures assume a well-loaded kiln – an empty or half-full kiln uses significantly more energy per fired piece. On average, a bisque firing is about 30–40% cheaper than a glaze firing in the same kiln, because the heating elements don't have to run at full load in the final phase.

Fully loaded kiln before the bisque firing: pieces may touch – a clear advantage over the later glaze firing.

If you want to calculate more precisely, you will find the complete electricity consumption formula and concrete model examples in our article How Much Electricity Does a Kiln Need for Ceramics?. There you will also find tips on night-rate electricity and dynamic tariffs, which can lower the cost of a firing even further.

A small note: The electricity costs alone are only part of the picture. Add to that the wear on the heating elements, occasional kiln maintenance and, if you don't fire yourself, firing service fees at other studios.

Can You Stack Bisqueware on Top of Each Other?

Yes, and that is exactly one of the big advantages of bisque firing. Unlike a glaze firing, where glazed pieces must never touch under any circumstances, bisqueware can touch, lean against each other and even be nested inside one another. A bowl inside a bowl, a small dish inside a large vase – all fine.

This has two practical consequences:

• You can load the kiln very efficiently. Anyone who fires regularly knows: a fully loaded kiln is not only more energy efficient, it also produces more even results, because the thermal mass stabilizes the firing schedule. That is why bisque firing is the firing where you can really save space.
  
  
• Firing several batches at once becomes possible. If you fire as a hobby potter every few weeks, it pays to wait with your first firing until you have enough pieces, and then run them stacked in a single bisque firing.

There is, however, a caveat that many people overlook: if your pieces are meant to stay unglazed after the bisque firing (for example for a later engobe technique or a raku firing with targeted reduction effects), you should not stack them. The reason: at the points of contact, locally different firing atmospheres develop, which color the iron in the clay unevenly. You then get lighter and darker patches where pieces touched. For pieces that will be fully glazed later anyway, this doesn't matter – the glaze covers it.

Rule of thumb: If you will glaze later, you may stack. If you want to leave it unglazed, better not.

Important here: don't put heavy pieces on top of delicate ones. And keep in mind that clay still shrinks a little in the bisque firing, usually only 1–2%. Most of the firing shrinkage happens later in the higher glaze firing. Still, if a handle or a thin wall sits too tightly against another piece, tension can build up as the clay shrinks.

What Do You Need to Watch Out for in a Bisque Firing?

Bisque firing is more forgiving than glaze firing, but it is not foolproof. Most beginner problems come from the same seven points. If you keep them in mind, you will usually end up with a clean, stable bisque body.

1. The clay must be completely dry.
This is the most common mistake and the one with the most dramatic consequences. Residual moisture in the clay turns to steam abruptly as the kiln heats up and can literally blow the piece apart. In the worst case, it takes the neighboring pieces with it. A rule of thumb: if you hold the piece against your cheek and it feels cold, it is still damp. If it is at room temperature, it is dry. How long that takes in practice depends on the type of clay, wall thickness and climate – more on this in our article How many days should clay dry before firing?

A cracked piece after the bisque firing: almost always a sign of heating up too fast or of clay that was too damp when it went into the kiln. Rule of thumb: in the critical zone of 100–600 °C, don't heat faster than 80–100 °C per hour.

2. Heat up slowly, especially between 100 and 600 °C.
This zone is the most critical of the entire firing. If the kiln heats up too fast, the remaining water cannot escape and the piece breaks. In this phase, stay at a maximum of 80–100 °C per hour. From 600 °C, the kiln can then run faster.

3. Plan a hold at the end.
15–30 minutes at the final temperature (usually 950 °C) make sure the heat distributes evenly in the kiln. Without a hold, pieces can be fired to different degrees in different spots, which only becomes noticeable in the glaze firing, when the glaze adheres unevenly.

4. Only open the kiln when it is cold.
The biggest temptation with the first firing: opening too early to see what came out. Only below 250 °C can you open the door a crack, and ideally you wait until it is below 100 °C to avoid stress cracks. It feels long – but it is the difference between intact and cracked pieces.

5. Never seal hollow forms airtight.
Anyone building a closed hollow form (a sphere, a sealed ring form, a sculpture) must leave a small air hole, usually invisible on the bottom. Trapped air expands enormously when heated and can burst the piece. A 1 mm hole is perfectly sufficient.

6. Check how you load the kiln.
Even though pieces are allowed to touch, the air still has to circulate, and there should be enough room between the levels for the heat. Use sturdy kiln shelves and posts; you will find suitable ones in our kiln furniture. Keep your distance from the heating elements, and don't place delicate pieces directly against the kiln wall. Rule of thumb: 2–3 cm (about 1 inch) of clearance from the walls and heating elements.

7. Check the kiln and the power connection.
Hobby potters in particular often underestimate whether their socket can handle 8–10 hours of full load continuously. A dedicated circuit, ideally installed by an electrician, is a must. For larger kilns from about 100 liters, you will usually need a three-phase power connection. More on this in our post Buying a kiln: What size, power and technology do you really need?

Bisque Firing and Glaze Firing: A Short Comparison

So you can see bisque firing in the bigger picture, here are the most important differences from glaze firing at a glance:

If you want to dive deeper – what really happens chemically during firing, which firing schedules suit which type of clay, and which final temperatures correspond to which glaze – you'll find it all in our basics article Firing ceramics: Basics, temperatures and technology explained.

Frequently Asked Questions About Bisque Firing

Do I have to glaze before the bisque firing?
No, quite the opposite. Glaze is only applied after the bisque firing. The porous body after the first firing soaks up the water-based glaze perfectly. If you glaze raw and only fire to bisque temperature, the glaze won't melt out and stays powdery. If you glaze raw, you have to fire straight to glaze temperature, see the next question.

Can I fire just once, without a bisque firing?
Yes, this is called single firing or once-firing and is practiced in some workshops, especially with stoneware. You glaze the unfired (leather-hard or dry) piece and fire it directly to the final temperature. This saves energy and time, but is technically much more demanding: the glaze layer has to be matched exactly to the state of the clay, otherwise it flakes off during heating. For beginners, the classic two-firing route is much more forgiving.

What is the best temperature for a bisque firing?
Most potters fire their bisque between 940 and 960 °C. For earthenware, the bisque firing is often a little higher, up to about 1,000 °C, because the glaze firing there is low and the body would otherwise stay too soft. For porcelain, the bisque firing tends to be lower, around 900 °C, so that the body stays absorbent enough for the glaze despite the fine clay. Important: the body should be firm but still porous, so don't fire too high, or it will no longer absorb the glaze properly later.

What is the difference between bisque firing and biscuit firing?
There is none. “Biscuit firing” is a synonym for bisque firing, and it is sometimes also called raw firing, red-heat firing or pre-firing. All of these terms describe the same process: the first firing, which turns the clay into a firm, porous body.

Can I apply engobe before the bisque firing?
Yes, in fact it is a very common technique. Engobes are usually applied to leather-hard or dry clay and then fired along with it – they bond firmly to the body during the bisque firing. So anyone working with engobe techniques treats the bisque firing not as a mere preliminary step, but as the first creative firing.

Can I fire ceramics again after the bisque firing?
Yes, that is actually the standard route. The bisque firing is followed by the glaze firing, and if necessary a third firing (for example for overglaze colors) can follow. We explain this in detail in our article Can you fire ceramics twice?

Conclusion: The Firing That Makes Everything Possible

The bisque firing is the unspectacular but indispensable step in ceramics. It turns fragile clay into bisqueware you can work with; without it, neither glazing nor safe transport would be possible. With a total duration of 20–36 hours and electricity costs between €3 and €18, it is one of the cheapest and most forgiving firings, and therefore the ideal introduction to the topic of firing.

Once you have understood that slow heating, complete drying and patience during cooling are the three most important variables, you have already avoided the majority of beginner mistakes. The rest is practice and the courage to just switch on the kiln.

If you don't have a kiln of your own yet, our kiln selection offers models from Kittec, Nabertherm and Pyrotec, from small 230 V entry-level kilns for home use to studio kilns for more serious work. We are happy to help you work out which model fits your plans in our free kiln consultation.

Note: The temperatures, times and costs mentioned are guideline values. Actual values depend on kiln model, type of clay, kiln load, electricity price and firing schedule. For the electrical installation and safe operation of a kiln, we recommend having it checked by a qualified electrician.

Have fun, the Formwerk Team!