Now that the clay quality was confirmed and he had a usable grate, Lin Yu'an returned to the cleared patch and set about building the ground‑level, rising‑flame kiln. He planned a compact kiln able to fire about twenty bricks per batch. That size balanced fuel efficiency and solo operability.
He began by digging a shallow foundation pit at the edge of the cleared circle. Using stones and mixed clay he formed a low circular base roughly 60 cm in inner diameter. On one side he left a 20 cm gap for the firewood feed and primary air inlet. He set the fired pottery grate inside the base, seating it level and secure. The grate would separate the firebox from the kiln chamber, support the bricks, and let hot air flow upward.
Next he mixed chopped dry straw into the kiln clay and built the kiln walls from the grate upward. He formed a roughly vertical cylinder with a smooth inner surface, about 60 to 70 cm tall so he could load and unload from the top. He kept wall thickness to roughly 10 to 15 cm to allow the kiln to heat up quickly and to save fuel. When finished, the kiln resembled a thick, lidless pottery jar with a circular opening of about 60 cm across. That top hole served as the loading mouth, a smoke vent, and an observation port; if needed it could be sealed with clay slabs.
After an afternoon of steady work the main body of the earthen kiln stood complete. Lin Yu'an patted the damp kiln wall and said to the camera, "The main body is done. Now it needs time to dry naturally so the moisture can evaporate." He used the drying interval to make molds and roof slabs. He had decided each brick would measure 20 cm long, 10 cm wide, and 5 cm high.
Using the mixed clay he formed a hollow rectangular mold with inner dimensions matching his target. He pressed out a number of uniform clay bricks and also formed several two to three‑centimeter thick clay slabs that would later cover the kiln roof. He smoothed edges and stacked the pieces in a ventilated corner of the shelter to air dry.
Two days later the kiln surface felt noticeably drier and the molds and roof slabs had hardened. Lin Yu'an announced, "It is time for a low‑temperature bake of the kiln." The purpose was the same as when he fired the test grate: remove residual moisture and induce preliminary sintering so the kiln would hold up under full firing.
He began the slow bake in the morning, lighting a small fire in the fire chamber and letting weak heat creep through the grate. With the top open the kiln vented steam freely. After several hours of gentle heat he increased the burn rate and kept a steady fire through the afternoon and into the night. The earthen kiln held heat much better than an open pit, so the internal temperature rose steadily. He judged the internal temperature by flame color and by the clarity of the smoke issuing from the top: when flames glowed bright orange and smoke thinned to near transparency, he knew firing temperatures had been reached.
That high‑temperature stage continued for seven to eight hours. When he judged the batch done he allowed the embers to settle into charcoal and stopped feeding the fire. Then he placed the air‑dried bricks and roof slabs on the grate through the top opening, leaving small gaps for air circulation, and sealed the roof with the clay slabs and wet clay to close any seams. He also sealed the firewood feed port so the kiln could warm and cool slowly overnight.
When the kiln cooled the next day Lin Yu'an approached with some nervous excitement. He cracked away the sealing clay and removed the roof slabs. Some fragments had fallen into the chamber, but most of the bricks and slabs were intact. He reached in and pulled out the first fired pieces. They rang with a crisp sound when tapped, a clear sign of good sintering.
"I did it," he told the camera, holding up a fired slab. "The molds and roof plates fired perfectly. Edges are a bit irregular, but the flatness and strength are good." He inspected the kiln body too; it had hardened and would now resist rain, though he planned to build a simple canopy to keep the fired bricks dry in storage.
The successful first firing proved the clay, the kiln design, and his process. With fired bricks and roof tiles available, he could begin producing more bricks and move on to stove construction and other projects that required reliable ceramic parts. He stacked the freshly fired pieces under cover, already thinking of the next batch. The kiln had moved his camp from improvised shelter toward a more permanent, self‑reliant settlement.