In the Yuan Dynasty, the emergence of underglaze red brought true high-temperature copper red into a controllable range, but it was still impossible to produce an overall red color.
Therefore, monochromatic red glazed porcelain is much more difficult to fire than painted red porcelain.
It is because of this that it was not until the Yongxuan period that the official kiln successfully fired the first porcelain in the history of the world with a ruby-like color throughout.
For example, the red glaze printed cloud and dragon pattern tall bowl from the Hongwu period of the Ming Dynasty is one of the representatives.
There is also a bright red glaze plate handed down from generation to generation, which was successfully fired during the Yongle period of the Ming Dynasty.
The most famous among them is definitely the Xuande bright red glaze plate of the Ming Dynasty.
In the Xuande period, there were also ruby red bottles, bowls, monk hat pots, rhombus style washbasins, and small lotus petal pots.
In addition to these, there are also some special porcelains, such as plates with gold dragon patterns, bowls with gold dragon patterns, etc.
In addition to using ruby red glaze, this time the porcelain also has gold color, which is gold painting.
If it were true, Chen Wenzhe must have avoided this kind of porcelain and would not be able to make it.
It's different now. He can learn the firing techniques of gold colors through the Sui Marquis Pearl, and with the huge amount of gold in his hands, he can naturally make porcelain whatever he wants.
However, for porcelain like this, even if he didn't try firing several furnaces, the chance of success would be very low.
This is not to mention that in the Ming Dynasty, the firing rate at that time was even lower!
Not to mention ruby red glaze, even if the underglaze red porcelain of the early Ming Dynasty was fired in large quantities, there were still many shadows of red that could not be seen at all, and it could almost be called underglaze black.
Therefore, for the production of red ceramics, the most important step is the firing process.
And because of the difference between single-color glaze or red painted glazed porcelain, the firing process is also different.
For this reason, red porcelain is divided into two forms. One is single-color glazed porcelain, that is, the porcelain is entirely red without any patterns.
Another kind of red glazed porcelain uses red paint to draw patterns, not all red.
On the surface, it seems that it is much more difficult to carry out detailed painting with copper red material than with a single tone.
The former is like using red to paint beautiful patterns on the wall, while the latter only needs to cover the wall.
From a painting perspective, there is no particular technical difficulty in flat painting, but painting requires years of study and training.
However, for the red color on ceramics, the firing process is the most critical technology.
Taking a step back, even if the red painted porcelain fails to be fired, the pattern is still there and you can still appreciate the splendor of the picture.
Many painted red porcelains in the early Ming Dynasty failed to be fired and the patterns turned black, but the patterns themselves were still wonderful and were treasured by later generations.
But a single red color is different. Poor color rendering in a certain part means the failure of the entire work, not to mention that the whole work cannot be burned red.
Therefore, porcelain that is completely red is much more difficult to fire than porcelain that is painted with red and has a red underglaze.
Chen Wenzhe has experience, time, and capital.
Therefore, he did not hesitate to consume a large amount of top-quality raw materials and kept trial-firing between making other porcelains.
After several firings in the kiln, Chen Wenzhe had a rough idea of the firing conditions of ruby red glazes in the Ming and Qing Dynasties.
After all, he has almost master-level kiln-burning skills. He is just unfamiliar with many things, rather than ignorant of them.
After another failed firing experience, he will pay attention. As long as he pays attention, he can easily find the problem.
Therefore, at this time, he already knew very well what to pay attention to when burning the kiln.
After all, the most important thing about red glaze is the kiln firing, especially the temperature control.
For example, the firing atmosphere, the reason why high-temperature red glaze is difficult is that to present a perfect red color, the firing temperature and atmosphere need to be precisely controlled.
The so-called firing atmosphere refers to the control of oxygen and carbon monoxide concentrations in the kiln.
Simply put, firing in an oxygen atmosphere is called an oxidizing flame, while firing in a carbon monoxide environment is called a reducing flame.
High-temperature red glaze needs to be fired with a reducing flame at a high temperature of 1300°C.
Why is red porcelain so difficult to fire?
Under ancient technical conditions, it was extremely difficult to control the firing temperature and atmosphere.
For example, temperature, in ancient times there was no equipment to measure and control temperature. The temperature in the kiln depends entirely on the experience of Master Bang Zhuang.
Master Bangzhuang is the potter in charge of firing the kiln. When it is fired, whether it is 1250℃ or 1300℃, you can imagine how difficult it is to just observe it with your eyes.
Of course, kiln workers gradually developed some methods to assist in judging the temperature.
But the control of heat still relies on experience.
In addition to temperature control, the concentration of carbon monoxide also needs to be adjusted accordingly.
What is the concentration of carbon monoxide at 1100℃? What is the concentration at 1200℃?
These need to be constantly adjusted, and what can be adjusted is only the amount of firewood and the speed of air circulation.
The reason why Chen Wenzhe's previous firing failed was because of this.
Although there are many modern monitoring devices that allow him to easily know the temperature inside the kiln, controlling the temperature and knowing the temperature are completely different things.
Especially when adding firewood, there is still air flow, especially the carbon monoxide concentration control. If you don't have enough experience and the number of firings is too few, it will be difficult to accurately control it.
You must know that wood kilns take a long time to fire. If there is a problem in any link during the long firing process of dozens of hours, all efforts may be in vain.
It can be said that every kiln firing is like a thrilling battle.
Therefore, before the Ming Dynasty, even if a little bit of local redness was occasionally burned, people would be amazed and even thought it was the care of God.
And the difficulty of burning it into a uniform red color is probably hundreds of times more difficult.
Not only is it difficult to bake, but the quantity that can be fired at one time is also limited.
There is another difficulty that is easily overlooked here, which is that the locations within a kiln that can meet the conditions for firing red glaze are extremely limited.
Within the kiln, the firing temperature and atmosphere vary greatly at different locations.
When the kiln is full, the kiln worker must consider in advance what porcelain is suitable for placement in which position.
In fact, most locations in the kiln are not suitable for placing red glazed porcelain.
In the industry, the location suitable for firing red glaze is even called "inch gold land".
It is very difficult and cannot be fired in large quantities, so one can imagine how precious the red glaze is.
However, it should be noted that in the past, pigments were all natural minerals, which were difficult to purify and had poor stability.
But with modern chemical technology, the purity and stability of the pigments are very high, so firing them is not difficult.
This was also the source of Chen Wenzhe’s confidence when he first started firing kilns.
Unfortunately, his failure rate was still too high, so high that he was afraid to accept it.
There is nothing he can do about it. Who makes him too worried?