Blue and White Porcelain Knowledge Series II: Understanding Blue and White Materials

 


 

classification of blue-and-white materials


1. Characteristics of several kinds of blue and white materials commonly used in the market at present

The so-called blue-and-white porcelain, the need to meet the three basic points:1, cobalt hair color;2. Underglaze color;3. The kiln temperature should be about 1300 ℃.Only the porcelain that satisfies afore-mentioned condition at the same time, can call blue-and-white porcelain!

The history of the development and use of blue-and-white materials is the same as that of blue-and-white porcelain, which has a long history.Different times, different raw materials, different use of the situation, there are great differences, if not professional practitioners, these too cumbersome expertise really does not need to be fully understood.

Then we from the lover’s actual combat angle, talks about the current market commonly used several blue and white material characteristic.

 

At present, there are three kinds of blue-and-white materials in the market: cobalt earth with complete mineral raw materials, cobalt oxide as the main synthetic raw materials, and mixed blue-and-white materials with different proportions in the first two.

 

The first kind of cobalt-earth ore with complete mineral raw materials is the source of blue-and-white material for making blue-and-white porcelain in ancient times.Cobalt-earth minerals from different regions, even cobalt-earth minerals from the same region will be different due to different mining periods (due to the change of the vein), so the made blue-and-white materials have different characteristics, ancient regions with different hair color and other characteristics to name and distinguish.In modern times, with a complete chemical knowledge system, it is more convenient to understand this distinction: cobalt earth ore is a deposit in the stratum, containing large amounts of cobalt ore, in addition, ore also contains other oxides, such as iron oxide, manganese oxide, potassium oxide, alumina, copper oxide, etc.The different proportion of ore layers in different regions leads to different hair color characteristics.

In ancient times, the production process of this kind of blue and white material is very troublesome, after cobalt earth mining or mountain pick up, first have to pick up, as not all the ore veins stone can open jade, cobalt earth ore also have to pick up first to meet the requirements, and then calcined.The first calcination temperature is about 900 ℃-1000 ℃, the second time is raised to 1280 ℃, according to the actual situation, it is necessary to carry out the third calcination.After that, the impurities need to be washed repeatedly, and iron-absorbing stones will be used to remove the iron impurities until the color turns blue.

This is not finished yet, and the calcined blue-and-white remains to be ground.The ancient productivity is low, the process is slowly in the porcelain mortar, this” slow “process, according to data data, it also takes at least three months.If grinding less than three months, the material is not thin enough, such a situation, a lot of times can not be normal use, even if reluctantly drawn out, but also because the blue and white material is not careful, resulting in the burning of the finished products appear a large area of barbed material problem.

This kind of blue-and-white material is made of complete mineral materials. The painters depend on their own experience and skill in the process of painting, according to the composition of blue-and-white flowers, tracing lines, and dividing water, according to the actual situation.For example, the thick directly used to trace lines, the need to separate water to achieve different depth of blue and white materials, according to the different proportion of water allocation, can be divided up to seven different colors, that is, the so-called “ink in seven colors.”Generally speaking, the ink is already very great.

 

The second, the synthetic raw material, which has been refined by modern technology, is mainly cobalt oxide. In a simple way, cobalt oxide is mixed with some other oxides, such as manganese oxide, iron oxide and so on, to produce the desired hair color characteristics.To painter, this kind of completely controllable modernized technological process, make color adjustment becomes very simple, reduce threshold difficulty, can buy the finished material of different hair color directly, for instance first-class white second-class white, for example green, second-class green, third-grade green, According to all kinds of blue and white materials to separate water can be.Of course, this kind of porcelain is basically used to make general goods, does not belong to our focus on the object.

 

The third kind is the mixture of modern cobalt oxide color and cobalt earth color with complete mineral raw material.This is also the mainstream of modern cobalt materials.

Through long-term experience summary, combine the progress of science and technology, our understanding to cobalt material is more and more comprehensive.We know that cobalt-earth minerals in different regions have different hair colors, and the difference is mainly due to the differences in the chemical elements they contain.In ancient times, for example, the study of Somerset was based on the study of Western Asia, that is, Persia, Iran, Turkey;The pearl material in early Qing Dynasty belongs to cobalt-earth ore in Yunnan;For instance, Zhejiang is the cobalt-earth mine in Jinhua, Shaoxing and Quzhou in Zhejiang.

The pure cobalt earth color, first calcining and washing cost is high, secondly this kind of color material is not easy to operate, when the brush-driven acerbity is serious.The painter draws on the porcelain tyre, from the starting pen to the setting pen between is cannot stop, the raw billet water absorption is especially good, once stops, the water on the brush is sucked away quickly, causes the drawing line not smooth.It is impossible to master a painter without some experience.An experienced and skilled painter’s salary is several times higher than the average painter’s, which will lead to a substantial increase in costs, so, in any way, it is not a good choice;

Modern technology to extract mainly cobalt oxide-based color materials, low production costs, easy to use painters, but the biggest problem lies in the burning of manufactured blue is very blue, very unnatural.

Today’s teachers will adjust the color mix according to different needs.It can also be said that, in fact, we see modern cobalt materials, more is through the deployment of.For example, Zhejiang material is no longer pure Zhejiang material, often add some Turkish cobalt or Yunnan cobalt material, better correct its hair color deficiency, so that hair color stability.

Of course, this kind of progress also provides support and convenience for archaize.According to the characteristics of different historical periods, it is also one of the main means of archaism to match the hair color.


2. Historically Blue-and-White Material

The history of the well-known blue and white material is probably divided into several kinds: Su Ma Li Qing, Equal Green (Pitang Green), Hui Qing, Ruizhou Stone Green, Zhejiang and Qing three generations of Zhejiang materials, Pearl (green blue).

 

Most of the cobalt deposits in the Siamaskashan area are recognized by us.Su Ma Li Qing is characterized by low-manganese high-iron, which is different from our domestic cobalt earth ore.The domestic cobalt-earth ore is low iron and high manganese.

Blue and white porcelain from the Yuan Dynasty to the Ming Dynasty Xuande, according to the research of most of the blue and white materials used for the Su Ma Liqing, of course, during the mixing of domestic materials.There are also said to be green clay.

As the iron content is high, the chemical reaction takes place after combining with the glaze. Iron oxide will crystallize when it cools. If the crystal is large, the surface of the crystal is mostly parallel to the glaze. The luster of metal is more obvious;On the other hand, due to the blue-and-white painting area, the ability to absorb the glaze pulp is weak, the position of the glaze is relatively thin, it is easy to appear tin spot situation or material prickles.

 

Equal Green (Pitang Green) is mainly used in Chenghua, Hongzhi and Zhengde years.Its origin is Jingdezhen Leping County, mainly characterized by high manganese and low iron.

 

Hui Qing is also a big characteristic of the Qing Dynasty.The Hui Qing of the Ming Dynasty in Jiajing will basically mix the stone blue, the Hui Qing is easy to faint, and the stone green is easy to turn black, the two mixed together to complement each other.According to the different ratio of Hui Qing and Shi Qing, different blue-and-white hair color can be adjusted.As a result, there has been a blue-and-white water.Generally they call the most correct hair color first-class green, used to line, light color used to fill the color.

 

After the mid-Wanli to Chongzhen years, Zhejiang materials began to become the main raw materials, Zhejiang materials are characterized by blue and blue ash.Qinghua materials used in the third generation of the Qing Dynasty are also based on Zhejiang materials, this period of great progress in the process, the purification of blue and white materials have been greatly improved, improve the blue and white faint situation, blue and white lines more clear.In addition, the addition of kaolin and kaolin in cobalt ore makes the blue-and-white color more stable.With these foundations, can appear Kangxi blue and white into five colors.

 

Pearl, also known as emerald blue.The pearl material is produced in Yunnan, the characteristic is very obvious, the hair color is green, the main appearance period is Kangxi middle and late period, Qianlong period, actually also appears in the late Ming Dynasty.

Zhuming materials are easily blackened in firewood kilns, and more serious in coal kilns in the sixties and seventies.We have burned many times in the firewood kiln. It’s really not easy to burn. It’s easy to turn black.

 


3. Causes of Influence on Colour of Blue and White

To be precise, every aspect of making porcelain has an effect on the finished product. According to practical experience, we have summarized four aspects that have a great influence on the color of blue and white: kiln atmosphere, kiln temperature, thickness of glaze, glaze formula.

 

Kiln burning atmosphere is summarized on two points: oxidizing atmosphere of the case, blue and white easily black hair black;If the atmosphere is heavy, it will turn blue.The result of the finished product directly, there will be smoking, blackening, and even as the iron oxide in the blue and white material is oxidized, there will be a red situation.

 

The effect of kiln temperature is also obvious, we use pictures for example, more intuitive.


Take a look at these two pictures first

This is an obvious sign of high temperature burning.We know that porcelain tire and glaze are integrated, in the kiln burning temperature is too high, if the body is relatively soft, then it will be directly cracked, in the case of the body is relatively hard, although not necessarily cracking, but enamel in the high temperature will naturally flow downward, Will drive down the whole picture deformation, resulting in the finished product of the entire picture fainting.


 

Look at these two pictures again

This is the low kiln temperature caused by the situation, on the one hand, the glaze did not completely melt and boil, on the other hand, blue and white hair color is not in place.

Low temperature, glaze does not melt, the transparency of glaze is not enough, that is, the degree of vitrification is not enough, not enough penetration.Natural cannot show the blue and white hair color under glaze very well;Add the low temperature caused by the blue and white hair color is not in place, black, black hair.

Below (the temperature is low on the left and high on the right)

The thickness of the glaze.We emphasized from the beginning that blue-and-white porcelain is underglaze, after painting the glaze.In this case, if the glaze is blown too thin, can not cover the blue and white material, in the firing process will produce a thorn;If the glaze is too thick, the original semi-transparent glaze will become hazy and frosted, will certainly affect the blue and white under the glaze color.

 

Enamel formulation.Before we discussed the problem of embryo glaze, we have introduced the general, here no longer elaborate.In fact, feldspar glaze and gray glaze of the final product difference is relatively large, there is intuitive picture contrast easier to understand.Let’s have a look at the pictures below.

 

Let’s first look at the blue-and-white porcelain made of high white mud and feldspar glaze from the gas kiln

 

Let’s take a look at the high white mud heavy blue and white water washing made from the kiln

 

Below is a blue-and-white porcelain made from antique mud and gray glaze

 

Old clay (imitation Kangxi, imitation Yongqian) with grey glaze