If you want to make porcelain, you can't avoid the five famous kilns, and if you want to imitate the five famous kilns of the Song Dynasty, you can't avoid nail firing.
Ru kiln, Guan kiln, Ge kiln, etc. mostly use supporting nails to support the firing. The shape is mountain-shaped, with the top pointed and the bottom rounded. There are different numbers of supporting nails on the round cake, and some have only one supporting nail.
Porcelain fired with pins will have small pin burn marks on the bottom.
Ru kiln has the smallest nail marks and is fragrant gray;
The nail marks of Guan kiln and Ge kiln are slightly larger and are iron-black in color.
Therefore, pin firing is used to apply glaze on the bottom.
This technology appeared very early and was a ceramic firing technology that became popular during the Five Dynasties period.
The specific method is to knead kaolin clay into "support nails" and stick these nails on the edges of the bowl and plate rings, each stack of 9-12 nails.
Then the bowl blank is placed on the support pillar, and then the bowl blanks with the support nails are overlapped to form a column and fired in the kiln.
Although this method can utilize the space of the kiln room and fire more products with the same specifications, it has drawbacks.
Since the flame is not separated from the product, it is easy to cause more waste products due to slag sticking;
At the same time, the support nails damaged the glaze on the inner bottom of the vessel, affecting the appearance of the product.
In addition, the number of stacks does not fully utilize the high altitude of the kiln chamber, which also greatly increases fuel consumption.
This is the kiln firing process. It turns out that Chen Wenzhe mainly involves temperature control, and he has never learned other aspects.
Now, through the inspiration of Zhupin firing, a lot of knowledge about kiln firing instantly emerged in his mind.
It can be said that when he saw the nail marks, he knew what kind of kiln firing process was used.
Although time passed by for a moment, he learned a lot of things, such as overlay burning, stacking burning, nail burning, and various kinds of burning!
This is an analogy. He had only been exposed to single-firing before. How could he have known that there were so many methods of kiln firing?
This time, through nail firing, we can study the firing technology of Yingqing in the Song Dynasty.
In fact, the last time he passed the high imitation Yuan blue and white piece, Chen Wenzhe saw the necessity of the firewood kiln.
However, whether in ancient times or modern times, burning firewood is very expensive.
It turns out that Chen Wenzhe thought that firewood in ancient times could be obtained for free. Obviously, this idea was wrong.
The more inheritance he received and the more he understood, Chen Wenzhe clearly understood that ancient labor and commodity prices were only relatively cheap.
It seems now that firewood in ancient times was not expensive, but in ancient times, ancient people felt differently.
In their opinion, burning kilns was also very expensive at that time.
The immersive experience is great because it allows him to take the place of others and experience their past.
During this period of time, I not only experienced their work, but also experienced part of their lives.
This is also the reason why Chen Wenzhe has all kinds of messy life experiences.
Through this analogy, I learned not only how to bake, but also the characteristics of various kiln mouths.
How to burn, what to use to burn, and how long to burn, all these need to be learned.
Taking the egg-shaped firewood kiln in Jingzhen in the Qing Dynasty as an example, it took four days to burn one kiln and consumed 22 tons of firewood.
These twenty-two tons are not just any dead branches and rotten wood. They must be two feet long and bowl-shaped pine wood, and they must be half dry and half wet.
Although there were many pine trees in the past, burning them once was quite expensive.
Although they all burn firewood, there are big differences between wood kilns, cha kilns and firewood kilns.
The egg-shaped kiln chamber covers an area of 80 square meters and is more than two meters high. A large part of the space in the kiln is wasted by the sagger.
However, saggers had to be used during that period, because when burning firewood, there would be a lot of smoke and ash, which would blacken the porcelain.
Therefore, the porcelain must be sealed and not come into contact with smoke and dust. This is the function of the sagger.
The sagger became popular in the Tang Dynasty, and there was also a kiln that specialized in firing saggers, called the sagger kiln.
There are big and small saggers, the big ones are for vases and the small ones are for cups and bowls.
They are all made of clay. To ensure strength, the wall of the bowl is relatively thick, about two centimeters.
From the photos sent by Professor Tao, we can see that the circle outside the fragments excavated from those sites is the sagger.
This kind of cooking method in which only one bowl is placed in a sagger is called single cooking.
The advantage of this firing method is that except for the unglazed circle at the bottom, the whole body is glazed, so it has been passed down to this day because modern people are not afraid of high costs.
In some photos, some bowls are stacked on top of each other, and the soil between them is the sagger.
It has been rotten for too long, but the general shape can still be seen.
The method of installing a single-fired kiln is very simple, that is, stacking many saggers with bowls in them, making lids on the top and the bottom on top, and adding a lid on the top.
The disadvantage of this burning method is that it wastes space. A one-meter-high stack of saggers only contains about twenty bowls.
The single firing cost is high, and it is generally used for fine porcelain, such as official kilns.
Low-end bowls and plates for folk use must reduce the cost of firing the kiln. The first thing that ancient porcelain workers thought of was that many bowls shared a sagger, which could save a lot of space in the kiln.
Wouldn’t it be enough to put it down like we usually put away bowls, and then put them in a tall sagger?
It's not that simple, there is also an adhesion problem here.
The glaze on porcelain is completely molten during the firing process and is still fluid. After cooling, it will stick to any object it comes in contact with.
If you directly fire a glazed bowl, you will get a bowl that sticks.
But the porcelain body will not stick. The porcelain we use now has an unglazed part at the bottom (perhaps in other locations), which is the part that is placed on the kiln plate when the kiln is fired.
The several firing methods that Chen Wenzhe originally knew were all designed to prevent porcelain from sticking.
Put down the bowl and place the sagger with the mouth of the bowl facing up. This is stacking.
How to prevent sticking? The most common way is to scrape off a circle of glaze inside the bowl, the same size as the base, and then put another bowl with an unglazed base on top.
If the bowls are only in contact with each other, they won't stick. This is called astringent ring stacking.
The porcelain fired in this way was used by Chen Wenzhe when he was a child. It was a large coarse white porcelain bowl with no glaze on the inner and outer rings, making it look particularly rough.
In addition, there are also methods of baking with a separator between the bowls, and adding a piece of clay, which is called stacking the cake.
There are also stacked burning of nails, stacked burning of support beads, stacked burning of sand, etc.
Regardless of the type of lamination, there is always a missing part of the glaze inside the bowl.
Therefore, these technologies will eventually be eliminated by the times.
Later, over-firing was developed, which is a method of firing bowls upside down. The most famous one was the Ding kiln in the Song Dynasty.
Place the bowl on a clay ring as big as the mouth of the bowl, called a support ring.
Put another supporting ring on the supporting ring, and then fasten a bowl. If you repeat this, you can lay down more than a dozen layers, and then put the sagger in it and bake it.
The overglazed bowls and plates, with only the rim unglazed, are called Mangkou.
Mangkou is a defect in the firing process. During the process of making and firing porcelain, the edges of the porcelain are unglazed and the fetal bones are exposed, which is called Mangkou.