Chapter three hundred and fifty-one blue and white underglaze red
The new work made by Chen Wenzhe naturally cannot be simple blue and white and multicolored. He plans to make a blue and white elephant-leg vase with red underglaze.
The decoration doesn’t have to be too troublesome, just two dragons, one red dragon and one blue and white dragon.
Making an elephant-leg vase is easy, and painting the cloud and dragon pattern is not difficult either.
As for the blue and white material, I use the best Qianlong blue and white.
If it's red glaze, it's a bit special.
Blue and white underglaze red, commonly known as "blue and white plus purple", is a porcelain decoration technique that uses underglaze red and painted patterns between blue and white.
Blue and white refers to using blue and white materials to depict patterns, then applying transparent glaze, and firing the underglaze color at a time with a flame of more than 1200c.
Underglaze red refers to a color material prepared with copper oxide (copper flower) as a colorant. Patterns are drawn on the body (or the green-white glaze is first applied to the clay), then covered with a layer of green-white glaze, and then installed.
The box is put into the kiln and subjected to strong fire between 1250c and 1280c, so that the high-priced copper is reduced to low-priced copper, showing a delicate and calm red pattern.
Does it look simple? In fact, it is not simple at all.
The most important thing is to control the temperature.
When firing blue and white, the temperature will only reach 1,200 degrees, preferably below 1,250 degrees, so that the color will be the best.
If the temperature continues to rise, the color of the blue and white will darken and become dull, which is very unsightly.
However, the glaze made with copper flowers as the toner is red in glaze, and the temperature required for firing it is higher.
Underglaze red is one of my country's traditional underglaze decorations. It uses copper as a colorant to draw various patterns on the body, and then applies a transparent glaze and then fires it in a high-temperature reducing atmosphere. The pattern is red, so it is called "underglaze red".
However, if you want the red hair in the glaze to be brightly colored, the temperature must exceed 1,250 degrees, and it must not be higher than 1,280 degrees.
The underglaze red fired in the Yuan Dynasty used color materials containing copper oxide as the colorant. Jingzhen called this color material "copper flower".
It is prepared by heating copper materials to obtain an oxidized surface layer, which is then carefully ground.
The color of this kind of color material is extremely unstable. Depending on the properties of the kiln's flame, it can appear green or cyan, as well as various shades of red or even flashing purple.
However, no matter what, the temperature must exceed 1,250 degrees for such color materials to develop normal color.
If the temperature is not reached, the hair color of the color material will be relatively dull.
Here, there is a contradiction between blue and white and underglaze red.
When the temperature is low, the blue and white will develop bright colors, but the red underglaze color will be very dull.
When the temperature is high, the color of blue and white will be dull, but the color of underglaze red will be bright.
That's it. Because it is difficult to produce qualified products, blue and white underglaze red products are extremely valuable.
Human beings have a root of inferiority, that is, the more difficult it is to do, the more they want to do it and the more they want to get it.
Therefore, although underglaze red can be decorated separately, most of them are combined with blue and white for decoration, so it is called "blue and white underglaze red".
Its characteristics not only have the "beautiful, elegant, quiet and stable" characteristics of blue and white, but also add the rich and magnificent underglaze red, enriching the color effect, forming an elegant yet simple artistic style.
Therefore, blue and white underglaze red porcelain has become one of the precious porcelain varieties in my country.
Judging from the existing archaeological and handed down materials, this craft technology has a relatively long history of development and maturity. After its creation in the Yuan Dynasty, it developed slowly in the Ming Dynasty, and there were not many successful products.
During the Kangxi period of the Qing Dynasty, the blue and white underglaze red craftsmanship was restored and developed, and there are many products with successful color development.
The Yongzheng period was the most mature and stable period for this underglaze color craft.
Most of the Yongzheng blue and white underglaze red vessels handed down from ancient times are bright and stable in color.
Although there were many blue and white underglaze red wares produced during the Qianlong period, the color development technology of underglaze red began to decline, and it declined again in the middle and late Qing Dynasty.
From here we can know that blue and white underglaze red is difficult to fire. The reason is not only the conflict between blue and white glazes and underglaze red, because even a single underglaze red is difficult to fire.
success.
What we are looking at here is the kiln-firing technique, and what Chen Wenzhe is not afraid of the most is kiln-firing because he has a master-level kiln-firing technique.
Originally he did not realize that kiln-firing technology was so important, but through repeated development and the more comprehensive kiln-firing technology he obtained, he discovered that this was the fundamental.
This time, he just thought of firing blue and white underglaze red porcelain, and once again acquired a lot of kiln-firing skills.
How to burn a kiln is a technology, controlling temperature is a technology, and how to control the temperature to make the utensils in the kiln, or to be more precise, how to make the color materials in the kiln develop color, is even more amazing.
technology.
When firing blue and white underglaze red, the main thing is to control the firing of the copper flower.
Copper flower, also known as copper oxide, is a very peculiar metal. It turns green when burned with an oxidizing flame, but can turn red only when burned with a reducing flame.
Under the reducing atmosphere, the copper oxide in the color material is reduced to cuprous oxide with a small proportion of oxygen, or pure copper without oxygen.
Like the high-temperature red glaze that also uses copper oxide as colorant, the red color of underglaze red when observed under a high-power microscope is "existing in a suspended state of fine particles of pure copper. The diameter of the copper particles is only about nine thousandths of a millimeter."
, approximate to colloid, and the color is different from that of ordinary metal."
This colloid "appears yellow when it is extremely small, red when it is slightly larger, and cyan when it is 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 the reducing atmosphere when firing the kiln.
That is to say, the color material in the kiln firing process will appear red when the reduction effect is appropriate. Excessive use will make the color darker.
When burned with neutral flame or oxidizing flame, it appears purple, cyan, or green;
If it is not completely melted, it will appear gray mouse or even dark purple.
If it is melted excessively, it will fade to orange or white.
In addition, copper is easy to flow and volatilize at temperatures above 800°C.
During the high-temperature firing process, it will melt with the top glaze and overflow through the glaze bubbles.
Therefore, only a small amount of copper is enough to produce red color. When the copper blending amount is less than 0.5%, the color produced is the best.
Therefore, it is also very important to control the copper content in color materials.
The firing temperature also has a great influence on the color development of underglaze red.
If the temperature is too high, all the copper will evaporate; if the temperature is too low, the glaze will become cloudy and the red color will not appear bright red.
Generally, the temperature is more suitable above 1200℃, and the maximum temperature cannot exceed 1280℃.
In order to avoid the volatilization of copper, the medium and high temperature stage of firing should not be too long, so the choice of kiln location when firing is also very relevant.
It can be seen that in the production of underglaze red, changes in various factors such as the preparation of color materials, the nature of the flame during the kiln firing, the temperature, the duration of the reducing atmosphere, and even the selection of the kiln location will all affect whether the product can present a pure red color.