In short, the characteristic of the production process of blue and white underglaze red is that the requirements of the two different firing processes of "blue and white" and "underglaze red" must be met at the same time during firing.
Among them, the coloring technology of underglaze red is very difficult and difficult to control. Therefore, it is not easy to fire two kinds of underglaze red products with perfect color.
It is precisely because of its complex firing technology and high difficulty that the number of productions in most periods was not large, and there are very few works that have survived to this day.
Less means higher prices.
On December 12, 2017, at the auction of a small auction house in Belgium, a Yuan blue and white remnant (never seen before) appeared. It has a resounding name "Yuan Dynasty Blue and White Underglaze Red Openwork"
"Peony Pattern Lid Jar".
Although this piece was "decapitated", uncovered, and pieced together in pieces, it still sold for 235,000 euros, equivalent to 1.8 million yuan!
This is a rare type of porcelain that is incomplete, incomplete, and can be sold at high prices after splicing.
Such porcelain is difficult to fire, but this is exactly what Chen Wenzhe needs.
Only by doing what others can't do or can't do can he show his ability. This can be regarded as mastering the core technology, right?
The elephant leg vase is just like a thigh, almost straight up and down, and the embryo is very easy to make.
It involves the mixing of color materials, painting and firing.
Yongzheng blue and white material, Chen Wenzhe can make Yongzheng blue and white material by using the ready-made Qianlong blue and white material and a little mixing. Copper oxide is not hard to come by, so he has already prepared these.
However, there is still a problem here.
He has never seen real blue and white underglaze red porcelain, and he doesn't know how to prepare underglaze red porcelain. How much copper is the best amount? Does it need to be added with some iron oxide?
The characteristics of underglaze red hair color in various eras are relatively obvious, so relying on the characteristics of underglaze red hair color is very helpful for the dating and identification of objects related to underglaze red.
For example, during the Qianlong period of the Qing Dynasty, the underglaze red was bright and the red color patches were not small.
It is estimated that not only copper oxide is used as glaze, but also mineral pigments such as iron oxide red and selenium red are used as glaze.
Calculating it this way, using Qing Dynasty technology is actually not the best choice.
Underglaze red was actually at its peak during the Ming Dynasty.
During the Hongwu period, the underglaze red hair color was often similar to black, which was also called underglaze black.
During the Hongwu period of the Ming Dynasty, there were many underglaze red porcelains, and their shapes and patterns were inherited from the Yuan Dynasty. The colors were light red and light gray, and few were pure.
However, in the Xuande Dynasty, the underglaze red was fired extremely successfully, forming a bright ruby red color.
It just so happened that Chen Wenzhe had just obtained a large pot made by the Xuande emperor, and he also knew something about ruby red. This time he chose Xuande ruby red to bake a red dragon.
These are actually different from the use of color materials. It is not difficult for Chen Wenzhe to combine various characteristics to complete the blend of underglaze red.
Anyway, this time he is not making imitations, he is just creating, and naturally he will do whatever he wants.
Once the embryo is ready and the color materials are mixed, painting and glazing begin.
When painting, Chen Wenzhe drew two dragons in a regular manner.
Originally, he thought of making two dragons entwined together, which would be the most beautiful. What he made was double dragons playing with beads.
But after thinking about it carefully, it is too troublesome to control the temperature when firing like this.
He had no choice but to have one on each side, and the last two dragons joined together at the head and tail of the dragon, and moved up and down.
The tail of the blue dragon chasing the red dragon is on the top, and the tail of the red dragon chasing the blue dragon is on the bottom. In this way, the two dragons are roughly distributed on both sides of the porcelain.
In this way, it is easier to control the temperature when firing one side at a time.
On the contrary, the key point is to properly prevent the volatilization of copper oxide.
Copper oxide will evaporate at temperatures above 800 degrees Celsius, but the temperature at which cobalt blue develops is as high as 1,200 degrees Celsius;
That's not all. The red glaze has the best color when it is between 1,250 and 1,280 degrees.
Therefore, it is somewhat of a fluke to maintain the blue and white and underglaze red colors at the same time.
Therefore, when firing underglaze red, the preparation of pigments and the production process from beginning to end must be very strict.
If there is a slight deviation, the entire kiln may be scrapped.
According to some historical records, it is lucky to be able to produce one of the ten red glazes!
This is the most realistic portrayal of the difficulty of firing underglaze red. What Chen Wenzhe is not afraid of the most is kiln firing. He has enough experience in inheriting this.
An elephant leg bottle was completed. Chen Wenzhe looked at the finished product and felt pretty good.
A red dragon steps on red clouds, chasing a blue orb.
A blue dragon, surrounded by blue clouds, chases a red orb.
The whole piece of porcelain has clear red and blue colors without any interlacing. This is the easiest way to control the temperature.
Of course, doing this is always a little bit meaningless.
Therefore, Chen Wenzhe made another elephant-leg vase with blue dragon and red cloud and red dragon and blue cloud.
In this way, the red and blue colors are mixed together.
If it is fired this way, the chance of success is relatively low.
However, the test items naturally progress from simple to difficult.
As long as he succeeds once, Chen Wenzhe is sure to succeed many times.
If the technology matures, he even wants to make a plum vase with a peony pattern, red peonies, blue leaves, bright red and blue, which should be more beautiful.
It's a pity that he has never encountered blue and white underglaze red, and he doesn't know the specific pigment formula. If he uses too much, the firing will 100% fail.
Once you have the finished product, you need to try it out by firing it in the kiln.
Anyway, if you want to burn a kiln, you cannot just open a kiln.
One sheep is being herded, and ten sheep are being herded, so he naturally wants to bake as many works as possible.
The Twelve-Flower God's Cup and the purple clay pot were put into two larger electric kilns separately.
Elephant leg bottles can only be fired using a small gas kiln, and only with this kind of kiln mouth can Chen Wenzhe accurately control the temperature.
After staying at home for two days, Chen Wenzhe's firing was about to end after a day and a half by constantly adjusting the temperature.
The next step is to open the kiln, which is like a scratch-off lottery. You will know whether you win or not by opening the kiln entrance and taking a look.
The other kiln entrances were only opened to cool down, but there were only six blue and white kiln entrances with red underglaze, which made him full of expectations.
Now that the firing was completed, he didn't want to wait any longer and went straight out of the kiln.
Carefully taking out the large elephant-leg bottles, he could tell at a glance that one of them had been fired successfully.
The elephant-leg bottle with red and blue separation can be easily fired as long as the temperature is controlled well.
However, although the elephant-legged vase at the entrance of the second kiln was also separated into red and blue and was a pair with the first one, it was still burned out.
This blue and white hair color is quite rich, but the red dragon is a mess.
There is a problem with the red glaze formula of this piece, so the fired red dragon turns green in some places, and is also gray and speckled, mixed on top of a red dragon, which is very ugly.