Constructing a Simple Pottery Kiln

Chapter Twenty-Three: Constructing a Simple Pottery Kiln

The sight of the two carefully shaped clay pieces crumbling to dust in the campfire was branded into Chen An's mind. The bitterness of failure had not yet completely faded, but the lesson he had drawn from it was exceptionally clear—a campfire could not meet the basic requirements for firing pottery. A pottery kiln that could concentrate heat and control temperature was the only path to success.

Once the thought took root, it grew like a rampant vine, quickly occupying his every waking thought. He immediately began pondering how to build the simplest possible pottery kiln of his own. He had no blueprints or examples to follow. All his knowledge came from the most basic physical principles and his observations of structures in nature.

The kiln's location was crucial. It could not be too close to the main house, to prevent high temperatures and smoke from affecting the living environment; nor could it be too far away, since transporting fuel and finished products would require manpower. In the end, he chose the southwestern corner of the Small Courtyard, near the downstream section of the stream from before, where clay resources were abundant. The area was relatively open, well-ventilated, and yet easy enough for him to control the wind direction. Its proximity to the water source would also make it convenient to process wet clay pieces or cool the kiln in the future.

He planned to build the simplest kind of vertical pit kiln. This structure was relatively sturdy and made it easier to concentrate the fire. He roughly outlined the kiln's shape: a vertical cylindrical or square earthen kiln, narrower at the top and wider at the bottom. The bottom would contain a firebox for fuel, while the upper section would be the firing chamber. There would also need to be a wood-feeding opening and a smoke outlet at the top or side.

Chen An first cleared the selected plot, removing the loose surface soil and stones. He carefully laid a solid foundation about half a meter thick with stones and compacted clay, ensuring that the kiln would not tilt or collapse because of ground settlement.

Next came the construction of the kiln walls. The first problem he faced was the material. Stones were readily available, but they varied in size and had irregular shapes, making it difficult to ensure a vertical and stable structure by stacking them directly. He tried using slurry—clay mixed with water—as a bonding agent. He mixed clay, sand, and a small amount of chopped dry grass into a primitive kind of "mortar." Using this mortar, he began stacking the stones one by one.

It was an extremely time-consuming process that demanded patience. The stones were heavy and difficult to transport. He constantly had to adjust their positions and angles to ensure that the walls rose straight upward. Sometimes the gaps between the stones were too large for the slurry to fill, making it difficult to ensure that the kiln was airtight. He had to experiment repeatedly, adjusting the mortar's proportions and striving to make each layer of stones fit together as tightly as possible.

He chose a square cross-section because a square structure was easier to keep stable while stacking. He planned for the kiln to be about one and a half meters wide at the bottom and about two and a half meters high, narrowing slightly toward the top, with a top opening roughly one meter in diameter. This size could hold a certain number of clay pieces without being so large that it became difficult to build and control.

Once the stone walls reached a certain height, Chen An thought of a crucial problem: stone conducted heat quickly and contained many gaps, so heat loss would be severe. He had to line the kiln walls. This reminded him of the batch of high-quality Pottery Clay he had discovered at the beginning.

He dug up some more fine clay. This time, he added more water and mixed it into a thick slurry with good adhesive properties. Using wooden pieces and his palms, he spread the slurry evenly and thickly across the kiln's inner walls. He did his best to apply it evenly, fill the gaps between the stones, and form a smooth, sealed clay lining.

This process was just as challenging. The slurry did not adhere easily to vertical walls and tended to run down. He had to apply it in sections, repeatedly pressing it down with his hands or wooden pieces to make it stick firmly to the stone walls. The interior space of the firing chamber shrank somewhat as a result, but this was a necessary sacrifice to improve heat retention and the chances of a successful firing.

He needed to install an openable kiln door in the lower part of the kiln for placing and removing the clay pieces. He left a square space in the layer of stones where he planned to install the door. Using several slightly smaller stones and specially prepared, thicker slurry, he made a movable square stone door. He carefully sealed the gap between the door and its frame with wet clay, striving to keep as much heat in as possible when it was closed.

About one meter above the kiln door, he opened a smaller circular wood-feeding hole for adding fuel to the firebox. This opening was also partially sealed with a thick stone slab or clay block with a hole in it. This allowed him to add wood while controlling the airflow to some extent.

How to vent the kiln from the top and control the airflow was a difficult problem. At the center of the kiln's roof, he slightly narrowed the stones inward, forming a circular smoke outlet about twenty centimeters in diameter. To control the smoke output and ventilation, he inserted a length of hollow, fairly sturdy bamboo into the outlet. If he could not find suitable bamboo, he would use a thick pottery pipe, or simply fit a movable pottery chimney sleeve over it. He could control the airflow by adjusting how deeply it was inserted. It was an extremely primitive method, but better than nothing.

Once the main body of the kiln was basically complete, Chen An coated the outer walls with a layer of wet clay mixed with straw. This reinforced the structure while also adding an extra layer of insulation. Around the kiln, he built a low wall from earth and stones to prevent rainwater from directly washing over the kiln's foundation and to help maintain the temperature around it.

The entire construction process lasted nearly half a month. Thick calluses formed on Chen An's hands, and his clothes were always covered in mud spots and bits of grass. Several times, cracks appeared in the kiln because of foundation settlement or structural instability, forcing him to repair and reinforce it again and again. On several occasions, exhaustion and frustration nearly drove him to give up, but whenever he thought of using pottery he had fired himself in the future, his desire to improve his life supported him as he picked up his tools once more.

In the end, a rough-looking vertical pit kiln filled with a primitive air stood in the southwestern corner of the Small Courtyard. It was built from stones of various sizes, its surface coated with rough slurry and bits of grass, with a crude smoke outlet at the top. It looked completely unremarkable, even somewhat on the verge of collapse, but Chen An knew that every stone and every inch of slurry embodied his hard work and his desire to survive.

He stood before the kiln, stroking its rough walls and feeling the heavy solidity of something created by human hands. This was more than merely a kiln. It was another cornerstone in his advance toward civilization. Next, he would clean out the firebox, light the first fire, and carry out the kiln's first firing—a genuine firing filled with the unknown. His heartbeat quickened again with anticipation.

(End of Chapter Twenty-Three)