Chapter 165: The Crystallisation of Clay and Fire
*Crackle crackle…* The fire in the earth kiln was burning vigorously, with the wood crackling loudly as it burned.
After Ru had finished glazing all the earthen bowls, Su Bai had people start the fire in the earth kiln, intending to proceed with the final step of making ceramics – firing the kiln.
“Shaman, are we going to throw these things into the fire to burn?” Yan Hua curiously pointed at the glazed earthen bowls.
“Of course not. If we did that, the ceramics would come out pitch black and might even get ruined.” Su Bai smiled. [You expect me to directly burn them? That obviously wouldn’t work.]
“Then, why did the Shaman ask people to start such a big fire?” Yan Hua blinked her red eyes curiously.
“This is the last step in making ceramics, called kiln firing. We’ll put the ceramics in after the fire has died down a bit.” Su Bai explained.
The process of kiln firing was a crucial step. If not done carefully, all previous efforts could be wasted, squandering raw materials, fuel, and a lot of manpower.
In ceramic craftsmanship, in terms of importance, it can be divided into first firing, second clay, and third glazing. In a sense, kiln firing was the key of keys.
Yan Hua regretted asking, as she obviously did not understand his explanation. She changed the subject, “Shaman, can we fire them right after applying that thing called glaze?”
“Yeah, that’s fine.” Su Bai softly said.“Shaman, how hot should we fire the kiln for it to be considered good?” Ru solemnly asked. Since he knew these were things he would need to master in the future, he had to learn carefully and ask about anything he did not understand.
“The temperature needs to reach over a thousand degrees, then we can put the ceramics in,” Su Bai explained.
“Over a thousand degrees?” Ru scratched the back of his head, confused, “Shaman, what does over a thousand degrees mean?”
“The temperature inside the kiln. I’ll give you a thermometer later, so you can gauge it better,” Su Bai said.
With the ‘Philosopher’s Stone’, getting mercury would be easy, and making a thermometer would not be too difficult.
“Thermometer?” Ru had heard many unfamiliar terms today, but he nodded and continued to ask, “Shaman, how long does this earth kiln need to be fired?”
“The kiln firing needs to continue for one night and the following day,” Su Bai solemnly said.
Everyone’s eyes widened upon hearing this, doubting if they had heard correctly.
“Shaman, does it really need to be fired for a day and a night?” Yan Hua asked in amazement.
“Yeah, and this is actually a relatively short amount of time. Some need to be fired for three to seven days.” Su Bai said, enunciating each word.
He naturally knew the difficulty of making ceramics. Many ceramics needed to go into the kiln several times.
This was just the firing time. Technically, they would need to calculate how much time the whole process took as a whole, from clay formation, painting, colouring, and so on. The total time for one ceramic piece was potentially very long.
“Three to seven days?” Ru looked astonished and exclaimed, “Shaman, isn’t that time too long?”
“That’s the time for making complicated ceramics. What we’re doing now does not need that long. A day and a night of firing will be enough.” Su Bai explained.
Ru put aside his surprise and began to get excited, asking, “Shaman, are there different firing techniques for ceramics?”
When he heard there was another technique for making ceramics, he became excited again. Eager learners were all like this. When they heard there was more to learn, they naturally became very curious and could not wait to learn them all.
“Don’t rush. Learn this technique first, there will be plenty of opportunities to learn the others in the future.” Su Bai gestured for him to calm down.
He had said this intentionally. Only by giving others something to look forward to would they strive to do better.
“Yes.” Ru immediately responded.
*Crackle crackle…* The fire in the earth kiln was burning vigorously, with the thick smoke that drifted out being very pungent. Following Su Bai’s instructions, they kept adding firewood.
To get the temperature inside the earth kiln to over a thousand degrees Celsius, they needed to keep adding firewood.
“Shaman, why don’t we just roast them directly over the fire pit?” Ru asked, puzzled.
“If we fire it that way, we would only produce defective products. It would just waste time and manpower.” Su Bai explained, enunciating each word. He recalled how in the past, people would pile straw on flat ground, place the clay bodies on top, and set it on fire.
However, because this would not be able to concentrate the fire to reach a certain temperature, and the fired pottery was of poor quality. Most were ruined, yielding an extremely low success rate.
Eventually, Humans invented pottery kilns. In the Neolithic Age, there were mainly two types of pottery kilns: Anagama Kilns and Pit Kilns.
Anagama Kilns were more typical, consisting of a firemouth, fire chamber, kiln chamber, flue and a kiln grate. The kiln chamber was round, with a grate at the bottom that had many holes for the fire. The flames from the fire chamber would reach the kiln chamber through the flue and fire holes.
In Pit Kilns, the kiln chamber was above the fire chamber. The fire chamber was a bag-shaped pit with a small mouth and a large bottom. It had multiple vertical flues leading to the kiln chamber.
The one Su Bai had people build was an Anagama Kiln, which was simpler to construct.
“So the Shaman had people build this earth kiln. You’re really so smart.” Ru was deeply impressed.
“In making ceramics, the most crucial process is kiln firing. You need to watch it closely.” Su Bai said seriously.
In the kiln, the high temperature produced by the wood fuel causes chemical reactions in the clay, leading to changes in the composition, properties, and colour of the clay body.
The structure of the kiln largely determines the firing temperature of the ceramics. The more rational the structure, the higher the firing temperature, and the more solid and durable the ceramics would be.
Moreover, the sealing condition of the kiln did not only affects the internal temperature but it also creates an oxidising or reducing firing atmosphere, influencing the colour of the ceramics.
Therefore, the kiln was the main indicator of the level of ceramic craftsmanship.
“Yes,” Ru responded very seriously.
Su Bai kept watching the flames burning inside the kiln, with flickering flames reflected in his black pupils.
His delicate face was illuminated by the orange-red glow of the flames. Apart from a hint of anticipation, his expression showed more concern.
Firing ceramics was not an easy task. Some might completely shatter during the firing process. Even if they came out intact, there could be cracks, or even peeling of the glaze applied before firing.
After more than half an hour, Su Bai estimated that the temperature inside the kiln had reached about 1200 degrees Celsius. Without accurate measuring instruments, he could only make a rough estimate.
He instructed, “The temperature is good. Start putting the ceramics in for firing one by one.”
“Yes.” Ru immediately responded, placing the glazed earthen bowls on a wooden board and slowly pushing them into the kiln.
“We’ll be able to see the results of this crystallisation of clay and fire tomorrow.” Su Bai said, the corners of his mouth slightly raised.
“Shaman, do we really have to wait until tomorrow?” Ru’s red eyes stared intently at the ceramics inside the kiln.
Su Bai nodded and instructed. “Keep a good watch. I’ll come back tomorrow to see how the results are.”
“Understood,” Ru nodded in response.
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