A lot of people have been wondering that the so-called china is only the bottles and jars fired by soil. Why is it so expensive and cost people a lot of money? Regardless of the pure artistic value, if we start with the origin of Porcelain, its expensive is reasonable indeed. At least, the cost of the ancient kilns was absolutely beyond imagination.
Take the egg type Kiln in Jingde town in Qing dynasty as an example, it takes four days to burn a kiln and cost 22 tons of firewood. Moreover, the 22 tons of wood were not any dead wood; they had to be two feet long’s pine trees, and half dry, half wet. Although there were many pine trees in the past, it was very expensive to burn.
Because of the large amount of soot and ash produced by wood burning, it is easy to smoke Porcelain into black, and the kiln workers usually close the porcelain with saggar to avoid contact with smoke. Therefore, the shell kiln is 80 square meters in area and more than two meters high, but a lot of space in the kiln is occupied by the saggar, which, to a large extent, adds to the burning cost of porcelain. The saggar was popularized in the Tang dynasty, and there was kiln which specializes in saggar, was called it box kiln. Saggar has big and small size, the big one can place vase and the small one place bowl. It's made of clay and it's about two centimeters thick.
The remnants of fu liang kiln in the song dynasty, the circle outside is the saggar. This saggar can only place a bowl, it’s called single burn. Its advantage is the whole body has glaze except for a circle of unglazed.
For the qinghua fragment of the Ming dynasty’s town kiln, the soil between the bowls is the saggar, it is broken because the time is too long, but you can still see the shape. The single-fired kilns are stacked with a large bowl of saggar. This is a waste of space, a pile of 1 metre tall’s saggar probably only have 20 bowls.
The single-fired kilns is high cost and usually used for fine china, such as official kilns. The low-grade bowl of the folk was low cost. The first thought of the ancient porcelain workers was that many bowls shared a saggar, which could save a lot of room in the kiln. It's not that simple. There's a problem of adhesion.
The glaze on China is completely fused during the firing process, and there is also the fluidity that will stick to any exposed object when cooled. If you burn a bowl with a glaze, you will get a sticky bowl. But porcelain tyres are not sticky, and the porcelain we use now has an unglazed part on the bottom (or perhaps somewhere else), which is where the porcelain was placed on the kiln plate.
Several of our firing methods are designed to protect against the adhesion of China. A pile of bowls were put into the saggar, this is the stack firing. How to prevent adhesion? The most important thing is to remove the glaze from the inside of the bowl, which is the same size as the bottom of the foot, and then put another one with a glazed bowl. The bowl will only contact the embryo, and it will not stick.
The bowl fired by the above method is mainly popular in the two generations of Jin and Yuan dynasties. This bowl is not beautiful and unhygienic, and the unglazed part of the middle is easy to get dirty.
In addition, there is a method of adding a piece of clay between the bowl and the partition, it’s called pancake firing method. There are also methods like nailing, beads, sand stacking and so on. Either way, the inside of the bowl is unglazed in somewhere. The most famous is Ding kiln in song dynasty. Place the bowl on a clay ring as large as the bowl mouth, and we call it a circle. One more lap around the branch, and another bowl, if repeated, it can carry over a dozen layers and then reloaded with saggar.
This is the overburn section, and the outer rings were put together, it is the same as this.
Covered firing dishes only burning mouth along the unglazed, called mang mouth, song dynasty royal has therefore abandoned ding kiln porcelain, the record is: "in the old capital, ding porcelain was not allowed to enter the royal family, so they can only use Ru porcelain, as ding porcelain has mang mouth". Some of the ding porcelain was wrapped in a circle of copper in the mang mouth, and the later counterfeits use black glaze instead of the copper ring.
Ding porcelain whose mang mouth is wrapped with copper rim.
There is two other rare way of firing: first, the two bowls were made to burn together. The bowl is set on top of the plate and the burnt dish is short of glaze. Burn, also known as a spike is used for stacking, and is famous for Ru kiln. It is estimated that the emperor of song dynasty pursued the acme of perfection and could not bear the unglazed porcelain. There are two kinds of firing ru kiln. One is to use clay to stick several nails on the bottom of the porcelain, and the other is to put the porcelain on a clay cake with a nail, and then burn it and knock it off. In all china, the branch of ru kiln is the most complete glazed porcelain.
Ru kiln plate, except for several nail marks, the whole body has glaze. The ancient secretary ru kiln is a "sesame nail", now many imitators understand it as the size of the sesame, the pin mark that has been made is round, this is a misreading. In fact, the nailing of ru kiln is sesame but flat.
The famous David bottle (also known as the blue flower cloud dragon's ear bottle), it’s the standard instrument for the cyan. It is faintly visible from the picture, under the two ears, with chestnut-sized stud marks. This is a rare type of burn method, a large spike directly supported by the saggar to avoid the vases tilting in the kiln.
Now the scene of firing kiln is: use natural gas, and gas kilns without soot, so it also needn’t to use saggar, just put porcelain directly on the kiln board.