Blue and white glazed red porcelain, why is it so expensive? Just look at its firing process!

Blue and white glazed red porcelain is a porcelain underglaze color decoration variety that was fired by the Jingdezhen kiln of the Yuan Dynasty by creatively combining the two underglaze color processes of blue and white and glaze red.

Although the blue and white glaze red in the Ming and Qing dynasties continued to be produced, due to the complexity and difficulty of its firing process, the number of productions in most periods was not much, and there are very few that have survived to this day.

Why a red remnant in a blue and white glaze

Can you sell for a high price?

First, the biggest feature of glaze red is that it is difficult to fire and the yield rate is extremely low.

It is based on copper as a colorant, directly on the white tire to draw a variety of patterns, on the top of a layer of glaze, copper in the high temperature reduction flame emitted red, so called "glaze red". Glazed red porcelain was created and fired in the Yuan Dynasty, but the number is very small, which can be described as rare.

Second, the red in the blue and white glaze is rare, and the well-preserved ones are extremely difficult to see.

Thousands of pieces of jingdezhen porcelain from the Ming Hongwu period were unearthed under excavators, the most dazzling of which was glaze red. Although they are all fragments, they do not affect their precious value at all. Once it appeared in the auction hall in the past, it was bound to attract attention.

On December 12, 2017, at the auction of a small auction house in Belgium, there appeared a yuanqinghua remnant (never shown), which had a resounding name "Yuan Dynasty blue and white glaze red opened and hollowed out peony pattern lid jar", although this piece was "beheaded", and it was not covered, it was pieced, but it still sold for 23,500 euros, equivalent to 1.8 million yuan!

Blue and white glaze in red porcelain

Process characteristics and difficulties

"Blue and white glaze red" refers to the underglaze color porcelain that is painted on the porcelain tire with two kinds of color materials, blue and white and glaze red, and then covered with transparent glaze and then enters the kiln to restore the atmosphere at high temperature for the next firing. The process basis of this variety is based on the characteristics of the two underglaze color processes of "blue and white" and "glaze red".

"Blue and white" refers to the underglaze color porcelain that is painted on the porcelain tire with green material containing cobalt oxide, and then covered with a transparent glaze, and the glaze that is fired under the glaze at a high temperature of more than 1200 ° C is fired under the glaze.

The advantage of the process of blue and white underglaze color is that the coloring power of cobalt material is strong, the color is bright, the atmosphere in the kiln has little influence on it, the firing temperature range is wide, and the color is stable.

Although the blue and white craft has been used as early as the Tang Dynasty Henan Gongyi kiln firing "Tang Qinghua" porcelain, but its real maturity and development is still realized in the Yuan Dynasty Jingdezhen kiln. "Glaze red" refers to the underglaze porcelain with copper oxide painted on the porcelain tire, then covered with a transparent glaze, and then fired in a kiln under the high temperature reduction atmosphere to show a red pattern.

The history of using copper as a colorant for ceramic underglaze can be traced back to the color decoration of underglaze brown-green colored porcelain in the Copper Official Kiln of Changsha in the Tang Dynasty. Modern scientific tests have shown that in the copper kiln color porcelain, it is often possible to see spots and simple flowers and grass patterns painted with brown or blue-green color, which is based on mineral raw materials with high iron content as pigments.

Blue-green color is based on mineral raw materials containing copper oxide or copper smelting slag as pigments, and after processing and grinding, they are formulated into color materials and applied to the surrounding parts of porcelain. This spotted color often flows when it is fired at high temperatures, and the green color that flows sometimes turns red partially, mainly because the copper oxide contained in it is reduced and colored.

Yuan Dynasty glaze red

The glazed red fired in the Yuan Dynasty also uses a color material containing copper oxide as a colorant, which Jingdezhen calls "copper flower".

It is an oxide surface obtained by heating copper and is prepared after careful grinding. The color of this pigment is "extremely unstable, with green or cyan appearing due to the different flame properties of the kiln, as well as various shades of red and even glittering purple".

If it is bluish green when it is fired with an oxidized flame, it can only be red when it is fired with a reducing flame. Under the reducing atmosphere, the copper oxide in the pigment is reduced to copper oxide with a small proportion of oxygen, or pure copper without oxygen.

Like the high-temperature red glaze that also uses copper oxide as a colorant, the red color of the glaze is observed under a high-power microscope as "in a suspended state of pure copper fine particles, and the diameter of copper particles is only about nine thousandths of a millimeter, which is similar to a colloid, and the color is different from that of ordinary metals." The colloid "appears yellow at very fine hours, red at a slightly larger, and cyan when larger."

Therefore, in order to reduce copper oxide to a suitable red pure copper fine colloid, it is very critical to grasp the nature of the flame in the kiln and the length of time spent reducing the atmosphere when firing the kiln.

That is, in the kiln process, the material "appears red when the reduction is suitable, and excessive will darken the hue." When fired with neutral flames or oxidized flames, it is purple, blue and green; if it is not completely melted, it will be gray rat color or even dark purple. If it melts too much, it fades to orange or white."

In addition, copper above 800 ° C has the characteristics of easy flow and volatilization, and will melt with the surface glaze and overflow through the glaze bubble during the high-temperature firing process, so that "only a small amount of copper is enough to appear red." The color is best when the amount of copper is mixed below 0.5%."

Therefore, it is also very important to control the copper content in the color material. The firing temperature "also has a great impact on the color rendering of the red in the glaze, the temperature is too high copper is all volatilized, the temperature is too low, the glaze is thick, and the red color cannot show bright red.

The general temperature is more appropriate around 1200 °C-1250 °C. In order to avoid the volatilization of copper, the firing stage should not be too long, so the choice of kiln position when firing kiln is also very relevant. ”

It can be seen that the production of glaze red from the preparation of color materials to the nature of the flame at the time of firing the kiln, the level of temperature, the time to restore the atmosphere, and even the choice of kiln position and other factors will have an impact on whether the product can present a pure red.

In short, the characteristics of the blue and white glaze red production process is that when firing, it is necessary to meet the requirements of the firing process of "blue flower" and "glaze red" at the same time, of which the color rendering technology of glaze red is very difficult and difficult to grasp, so it is not easy to make the firing of two kinds of underglaze color perfect products.

Judging from the existing archaeological and heirloom materials, the history of the mature development of this craft technology is indeed relatively long, and it has developed slowly in the Ming Dynasty since it was created and burned in the Yuan Dynasty, and there are not many successful products.

During the Qing Kangxi period, the blue and white glaze red process was restored and developed, and there were many products with successful hair color. The Yongzheng period is the most mature and stable period of this underglaze color process, and most of the red vessels in the Yongzheng blue and white glaze that have been handed down are bright and stable. In June 2019, Beijing Poly, a Qingyongzheng imperial blue and white glaze red cloud sea Tenglong big sky ball bottle, auctioned a sky-high price of 147 million, which shows its preciousness!

Due to the difficulty of firing, the red in the blue and white glaze has always been valuable and very precious, if it is fired in a wood kiln, the stability is even more uncontrollable, and "nine out of ten kilns" is a common thing.

In order to make both have a good hair color, it is necessary to start from the glaze configuration, including the grasp of the atmosphere and temperature in the kiln, etc., the entire production process is very strict, and the slightest mistake will abandon the previous work.

Therefore, the firing of red in the blue and white glaze is controlled by experienced old kiln workers. But even so, there are few finished products, and even the kiln is damaged. It is difficult to describe its fine products with a hundred kilns, and it is even more than enough.

Because of this, the red porcelain in the blue and white glaze is fired in the official kiln, and most of them are the works of the prosperous period, and the folk kilns must not be done. After all, these kilns fired porcelain to make money rather than lose money, and no one risked ruining their home for a piece of porcelain.

Blue and white glazed red porcelain not only reflects its preciousness and achievements in craftsmanship, but also has a rich cultural connotation, coupled with its rare characteristics, no matter where it is located, it should be the most shining highlight.

It is a symbol of national strength and an object of the emperor's enjoyment. Every blue and white glaze red work is a natural object that cannot be missed.

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