# Pit Firing: The Oldest Kiln in the World

Unit: Alternative Firing Methods
Topic: Pit Firing and Barrel Firing
URL: https://claybook.studio/learn/pit-firing-the-oldest-kiln-in-the-world/

# Fire in a Hole

Pit firing is the oldest known ceramic firing method, used by human cultures for at least 20,000 years. There is no kiln: just a hole in the ground, fuel, and fire. The technique produces naturally decorated surfaces with rich, flowing colours of black, orange, red, and grey that cannot be replicated by any kiln-based method.

## How Pit Firing Works

*   Dig a pit roughly 60-90 cm deep and wide enough to hold your pieces with combustible packing material around them.
*   Line the bottom of the pit with a layer of combustibles: wood shavings, newspaper, dried leaves.
*   Place bisque-fired or raw greenware pieces in the pit. Pit firing can be done with unfired greenware, but bisque pieces are more durable and produce more reliable results.
*   Pack combustible materials around and between the pieces. Organic materials like banana peels, copper wire, seaweed, salt, and metal oxides placed against the clay produce localised colour effects.
*   Cover the pieces with more combustibles, then add larger wood on top.
*   Light the fire from the bottom. Allow it to burn down completely (typically 3-6 hours).
*   Let the pit cool completely before removing pieces. This can take many hours or overnight.

## The Colours of Pit Firing

The patterns and colours in pit-fired work come from:
*   **Reduction zones**: Where oxygen is scarce, black and grey marks develop.
*   **Flame paths**: Orange and red where direct flame touched the clay.
*   **Colourants**: Copper wire produces greens and pinks; iron oxide washes create reds and blacks; salt creates white halos.

## Down the Rabbit Hole

Pit firing is the oldest known ceramic firing method, with [earthenware](https://en.wikipedia.org/wiki/Earthenware) vessels produced this way for at least 20,000 years. Many contemporary pit-fire artists apply [terra sigillata](https://en.wikipedia.org/wiki/Terra_sigillata), an ultra-refined clay slip originally developed in the Roman period, to burnish their pots before firing for a smooth, lustrous surface that shows the fire's marks with exceptional clarity.

## Safety and Process Discipline

*   Keep a clear perimeter around the pit and assign one fire manager.
*   Never remove pieces until fully cooled; hidden heat can still crack ware when exposed too quickly.
*   Photograph each packing setup before lighting so you can learn from results.

## Pro Tip

Use small repeatable bundles of colourants tied in paper. Consistent packet size makes your experiments more comparable firing to firing.

## Check your understanding

### Question 1: What produces the black and grey marks in pit-fired pottery?

- [ ] A. Black clay body shows through where the glaze burned away
- [x] B. Reduction zones where oxygen is scarce cause carbon absorption in those areas
- [ ] C. The pit's soil minerals transfer to the clay during firing
- [ ] D. Black pigment is applied to the pots before placing them in the pit

Tip: Black and grey marks form in reduction zones: areas inside the pit where oxygen is scarce. Where direct flame contacts the clay, orange and red tones develop instead.

### Question 2: Can raw, unfired greenware be pit fired, and should you?

- [ ] A. No: only glazed pieces can be pit fired
- [x] B. Technically yes, but bisque pieces are more reliable and less likely to crack
- [ ] C. Yes, and raw greenware produces better colours than bisque
- [ ] D. Greenware must be bone dry for at least a month before pit firing

Tip: Raw greenware can technically be pit fired, but bisque pieces are more durable and produce more reliable results. Greenware is fragile and more likely to crack from thermal shock during the rapid temperature changes.

### Question 3: Why is photographing your pit packing layout before lighting useful?

- [ ] A. It helps estimate cooling time by counting fuel pieces
- [x] B. It creates a repeatable record so you can link outcomes to loading choices
- [ ] C. It prevents thermal shock by documenting fuel moisture
- [ ] D. It is required for insurance in all outdoor firings

Tip: Pit firing is highly variable. A photo record lets you connect later surface results to exact placement, fuel density, and colourant contact, improving future decision-making.