Here is how you turn this into this.

But if you rush the process, everything can crack or explode. I learned that the hard way.

In this tutorial, I will share primitive firing techniques that I have developed through trial, error, and research. These methods will help you fire pottery successfully in your backyard without excessive breakage.

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Understanding Clay and Heat

It helps to understand what happens to clay when you heat it.

Clay is plastic and pliable when wet. After firing, it becomes hard and durable.

Chemically, clay contains alumina, silica, and chemically bound water. However, natural or commercial clay is not pure. It is a clay body that includes sand, organic material, and other impurities.

During firing:

• Organic material burns away.

• Water is driven off.

• The clay shrinks.

At higher temperatures, alumina and silica begin to fuse together. This process is called sintering. At sintering temperatures—commonly achieved in pit firing—the clay becomes durable and will no longer dissolve in water, though it remains porous.

At even higher temperatures (around 1300°C or above), the clay becomes vitrified, meaning it melts into a glass-like structure. Pit firing does not typically reach vitrification temperatures.

Rapid shrinkage from fast heating causes cracking or explosions. Slow, controlled heating is essential.

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Step 1: Making the Pots

Hand-building is the oldest method and requires only clay and a basic surface.

A scrap of canvas works well as a work surface. A rotating cake stand can help, but a board or countertop is sufficient.

Important considerations:

1. Do not over-invest emotionally in your first pots. Breakage is common while learning firing techniques.

2. Maintain even wall thickness. Thin and thick areas shrink at different rates and may crack.

3. Use coarse clay (grog clay).

Grog is pre-fired clay that has been crushed and added back into clay. It reduces shrinkage and cracking. Clay marketed for raku or atmospheric firing typically contains grog.

If using smooth clay, you can crush previously fired pottery and wedge it into your clay as grog.

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Step 2: Drying and Oven Preheating

Let pots air-dry for several days until bone dry.

Then preheat them in a household oven:

• Start at 200°C.

• Gradually increase to 500°C over 1–2 hours.

• Hold at 500°C for at least one hour.

This step removes remaining moisture. Even bone-dry pieces can still lose 5–10% weight in the oven.

The oven will not sinter the clay, but it prepares it for pit firing.

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Step 3: Preparing the Pit

Dig a pit deep enough to hold the pots below ground level. The shape does not matter.

Start a small fire in the pit to dry out the earth. Moisture is the main cause of explosions during pit firing.

Use dry fuel. Wet or green wood pops and can break pottery.

Allow the pit to heat and dry for some time before adding pots.

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Step 4: Gradual Heating

Place oven-dried pots near the fire to warm gradually.

Think of it like sitting by a fire: you get warmer slowly before getting very hot. Do the same with your pots.

• Keep a small fire.

• Rotate the pots for even heating.

• Avoid direct flame at first.

• Be patient.

This gradual heating may take about an hour.

You may cover the pots with scrap metal to create a small heat chamber.

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Step 5: Coal Stage

Let the fire burn down to hot coals.

Rake out a clear space in the centre. Place pots in this space so they are surrounded by heat but not directly buried in coals.

Continue heating gradually for 30–40 minutes. Add small pieces of wood as needed.

Leather welding gloves can help you reposition pots safely.

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Step 6: The Main Fire

Build a larger fire over the pots.

Add wood gently to avoid knocking or cracking them.

You may maintain the fire for about an hour.

If visible, glowing red pottery indicates approximately 900°C, which is typical for low firing.

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Understanding Colour in Pit Firing

Clay colour changes due to smoke and vapours entering the porous surface while hot.

When clay cools, the pores close and trap those colours.

Black (Carbon Trapping)

To achieve jet black:

• Smother hot pots in sawdust, dry grass, or pine needles.

• Completely cover them.

Carbon becomes trapped in the clay body.

Other Colours

Minerals in the fire release vapours that create colours. For example:

• Copper can produce green tones.

Be cautious: some materials (such as salt) can release toxic fumes.

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Step 7: Reduction Atmosphere (Optional)

Covering the fire while still hot reduces oxygen. This creates heavy smoke and encourages colour development.

You can experiment:

• Let pots cool naturally.

• Remove a hot pot and smother it for black effects.

• Combine techniques.

Avoid rapid cooling, especially with smooth clay bodies, as thermal shock can cause cracking.

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Final Results

Pit-fired pots will:

• Be sintered (if hot enough).

• Resist dissolving in water.

• Remain porous.

They are not vitrified and are not suitable for food or liquids. However, they are suitable for decorative use or holding dry materials.

Some pieces may break. Others may survive beautifully.