Bisque Firing vs. Glaze Firing: What’s the Difference?

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If you’re new to pottery, you may hear terms like bisque firing and glaze firing and wonder: What’s the difference? Why does pottery need to be fired twice?

These are two different stages of the ceramic process, and understanding the difference will make pottery much easier to understand.

In simple terms:

Bisque firing turns dried clay into a strong, porous ceramic piece. Glaze firing transforms the glaze into the finished surface.

Let’s break down what each firing does and when you need it.

What Is Bisque Firing?

Bisque firing is usually the first firing your pottery goes through.

Before bisque firing, your piece is called greenware. It has been shaped and completely dried, but it is still unfired clay.

During the bisque firing, the kiln heats the pottery to a temperature that permanently changes the clay.

Water and other materials leave the clay, and the clay particles begin bonding together.

The result?

A piece that is much stronger and easier to handle—but still porous enough to absorb glaze.

Why Is Bisque Firing Important?

Imagine trying to glaze a fragile, unfired clay mug.

It would be extremely easy to damage.

Bisque firing gives the pottery enough strength to make glazing much easier.

It also creates a porous surface that allows liquid glaze to adhere to the pottery.

That’s why bisque firing is such an important step for most glazed pottery.

What Is Glaze Firing?

Glaze firing happens after the pottery has been bisque fired and glazed.

Once the bisque-fired piece has been cleaned and decorated with glaze, it goes back into the kiln.

This time, the goal is to mature the glaze and finish the ceramic piece.

During the firing, the glaze materials soften and melt. As the kiln cools, they solidify into the glass-like surface you see on the finished pottery.

This is where your piece can develop its final:

• Color
• Gloss or matte finish
• Texture
• Opacity
• Decorative effects

Why Fire Pottery Twice?

The two firings serve different purposes.

Bisque firing = prepares the clay.

Glaze firing = finishes the pottery.

Trying to combine everything into one firing is possible in some pottery processes, but it requires different techniques and is generally less forgiving for beginners.

For most beginners, the two-step process is much easier to control.

What Happens to the Clay During Bisque Firing?

During bisque firing, the clay undergoes several permanent changes.

As the temperature rises:

1. Remaining moisture leaves the clay.
2. Organic materials burn away.
3. Chemically bound water is released.
4. Clay particles begin bonding.
5. The piece becomes a stronger ceramic material.

The important thing to remember is that bisque pottery is no longer ordinary clay.

You cannot simply add water and turn it back into workable clay.

However, it is still porous, which makes it ideal for applying glaze.

What Happens During Glaze Firing?

Glaze firing focuses heavily on the glaze.

As the kiln reaches the glaze’s intended firing temperature, the glaze materials soften and develop into a glass-like coating.

The exact result depends on the glaze chemistry, firing temperature, clay body, thickness of the glaze, and firing conditions.

That’s why the same glaze can sometimes look different on different clay bodies or at different firing temperatures.

Which Firing Is Hotter?

There isn’t one universal answer.

The correct temperature depends on the clay body, glaze, and firing schedule.

A bisque firing is often done at a lower temperature than the final glaze firing, but this is not a rule that applies to every pottery process.

Always follow the firing recommendations for your specific clay and glaze.

Never assume that every clay or glaze can be fired at the same temperature.

Can You Glaze Greenware?

Technically, some pottery techniques allow glaze to be applied to unfired clay, but this is not the typical beginner workflow.

For beginners, the usual process is:

Shape → Dry completely → Bisque fire → Glaze → Glaze fire

This gives you more control and makes the glazing process easier to manage.

What Happens If You Glaze Bisque Ware Incorrectly?

Glazing may look simple, but the amount and application matter.

Too much glaze can cause it to run during firing and potentially stick to the kiln shelf.

Too little glaze may leave the surface patchy or produce a different result than expected.

Some glazes also require specific application thicknesses and firing temperatures.

That’s why it’s a good idea to follow the glaze manufacturer’s instructions and test unfamiliar glazes before using them on important pieces.

How Long Does Each Firing Take?

There is no single firing time for every kiln.

The firing time depends on factors such as:

• Kiln size
• Amount of pottery inside
• Clay type
• Glaze type
• Target temperature
• Firing program
• Thickness of the pottery

Both firings can take several hours to heat up, followed by additional cooling time.

So don’t expect to load a kiln in the morning and immediately have finished pottery a few hours later.

The cooling period is part of the process too.

A Simple Example

Imagine you’ve made a ceramic mug.

Step 1: Shape It

You make your mug from wet clay and allow it to dry completely.

Step 2: Bisque Fire It

The mug goes into the kiln for its first firing.

Afterward, it is hard and porous.

Step 3: Glaze It

You apply your chosen glaze to the bisque-fired mug.

Step 4: Glaze Fire It

The mug goes back into the kiln.

The glaze melts and develops its final surface.

Step 5: Cool and Unload

Once the kiln has cooled sufficiently, you can finally see the finished mug.

That’s the basic pottery firing journey.

Bisque Firing vs. Glaze Firing: The Easy Way to Remember

If you’re just starting pottery, remember this:

Bisque firing changes the clay.

Glaze firing finishes the surface.

That’s the biggest difference.

You don’t need to understand every chemical reaction to get started. Once you understand what each firing is supposed to accomplish, the entire pottery process becomes much easier to follow.

Final Thoughts: Don’t Be Confused by the Two Firings

If you’re new to pottery, hearing that your work needs to go into the kiln twice can sound complicated.

It’s actually quite straightforward.

The bisque firing takes your fragile, unfired clay and turns it into a stronger, porous ceramic piece.

The glaze firing then transforms the glaze into the finished surface.

So when you make your next mug, bowl, vase, or sculpture, think of the kiln as having two important jobs:

First, transform the clay.

Then, finish the piece.

Once you understand that difference, bisque firing and glaze firing become much less confusing—and you’ll have a much better idea of what’s happening to your pottery every step of the way.