After a cultural relic is damaged, there are some benefits.
Because destroyed cultural relics are more convenient to study.
It is not afraid of being damaged again, but it just allows researchers to better understand the Song Dynasty Ge kiln wares by looking at the internal performance.
For example, you can look more carefully at "Jumo and Zhuzhu".
The exact origin of the term "Jumo Chanzhu" has not yet been found.
However, some people say that it was Song Huizong who said it, but Chen Wenzhe has doubts about this statement.
Because to see the small bubbles under the glaze, you need to use a magnifying glass to observe.
In the Song Dynasty more than a thousand years ago, although technology was still quite advanced, they didn't have enough money to own a magnifying glass!
So how did Zhao Ji see this phenomenon? If it is Juqiu, then it is easy to understand.
However, many classic records refer to gathering foam and gathering pearls!
Mr. Sun Yingzhou's book "Appraisal of Yuan, Ming and Qing Porcelain" mentioned: "Like an official, the glaze bubbles are as dense as pearls."
What exactly does "gathering together foam and gathering pearls" refer to?
In fact, you can "meet the words" here.
Let’s talk about “mo” first. Mo refers to foam.
Bubbles are explained in Baidu Encyclopedia as “many small bubbles gathered together.
A dispersion system formed by insoluble gas dispersed in a liquid or molten solid." Let's talk about "beads".
They are many small bubbles that aggregate into large bubbles, which are called "beads".
Among the other two verbs, "gather" refers to the state of bubbles being close together and gathering together. Bubble is the state of small bubbles gathering together;
The word "zan" has two pronunciations, one is zan, which means accumulation.
Here Chen Wenzhe believes that it can be understood as bubbles superimposing each other and gathering together.
Another pronunciation is that it is assembled with ready-made parts, which means that the bubbles will have a series of characteristics.
Through this analysis, Jubu Chuanzhu refers to the bubbles under the glaze.
The formation of bubbles on the glaze is caused by many factors.
For example, glaze formula, glaze viscosity, firing process, etc.
Generally speaking, there are probably several reasons.
The first is the internal cause, which is the bubbles produced by the reaction of the tire glaze itself.
There are many pores in the carcass, some open and some closed.
When the temperature rises, the gas expands, and the gas in the open pores enters the glaze layer and is discharged.
When gas escapes the glaze layer, two glaze defects will occur.
One is that small bubbles gather in the glaze to form large bubbles, which will form a crater when impacting the glaze surface.
If the viscosity of the glaze layer is small, it can return to flatness.
But sometimes, pinholes still appear.
The other is the discharge of bubbles, which will produce pits on the glaze.
In addition, as the temperature increases, the glaze layer melts into a liquid phase to moisten the body.
Due to the liquefaction of the glaze layer, it is easier for the gas in the carcass to be discharged through the glaze layer.
The gas that is not discharged remains in the glaze to form bubbles.
In addition, the substances contained in the tire decompose at high temperatures and produce gas emissions.
For example, the crystal water of some minerals will also become gaseous and be discharged at high temperatures.
For example, some sulfides, nitrogen compounds, carbonates, etc. will produce corresponding nitrogen, sulfur dioxide, carbon dioxide and other gas emissions.
The specific chemical principles will not be repeated here. Modern people should know it after graduating from middle school.
The last reason is that at high temperatures, carbonate decomposes to release carbon dioxide gas.
After cooling down, carbon dioxide is absorbed and reduced to carbonate, which is a reversible reaction.
The more basic a metal is, the higher its decomposition temperature is.
Glass solution has the property of dissolving carbon dioxide, but its solubility changes with changes in alkalinity and temperature.
The stronger the alkalinity, the higher the solubility, the higher the temperature, the smaller the solubility.
The glaze is much less alkaline than alkali silicate glass, so the solubility of carbon dioxide is very low.
So carbon dioxide will be released, creating bubbles.
Then there are external factors. This is because the process affects the generation of bubbles.
The dried glaze layer has poor air permeability and the air in the tire is not easily discharged.
At high temperatures, the gas in the tire passes through the glaze and creates bubbles when it is released outward.
During rapid firing, the gas in the tire and glaze has no time to escape, and is sealed by the melted and hardened oil layer, forming bubbles.
Finally, the effect of temperature on bubble production.
The body and glaze of porcelain often contain feldspar and quartz.
They account for a large proportion of the formula system. According to research, bubbles begin to appear at 900°C.
At 1025°C, the gas volume ratio is maximum.
When reaching 1100°C, the bubbles gradually disappear from the melt.
At around 1240°C, the glaze melts and a large number of small bubbles appear.
Most of these bubbles are distributed in the middle of the glaze layer. As the temperature increases, the viscosity of the glaze melt decreases, and the amount of gas phase and glass phase increases.
Due to surface tension, small bubbles will move and merge.
From small to large, from more to less, and it will rise.
There are even some bubbles that will break through the glaze and be released.
If the viscosity of the glaze is high and the surface tension is low, the depressions left by gas release will not be easily filled, causing defects in the glaze.
When the temperature reaches 1300°C, the rate of bubble rise and growth slows down.
Under normal circumstances, when the glaze maturity temperature is reached, most of the bubbles that have not been discharged are deep in the glaze layer, at the junction of the glaze, and are small in size.
So what significance do the bubbles generated under the glaze have on porcelain?
In fact, bubbles in the glaze can be regarded as a flaw in the porcelain glaze.
It is a flaw that is difficult to avoid during the firing of porcelain, and even some unavoidable defects at the kiln entrance.
Even when making ceramics in modern times, they will consider how to reduce the defects caused by bubbles to the porcelain.
This problem is mainly pitting, depressions, craters, etc.
However, the bubbles on the glaze are similar to the cracks, turning from a flaw into a pursuit of beauty.
A glaze with bubbles will eliminate some of the shine.
This will produce a certain sense of opacification, making the porcelain glaze appear more oily, plump and layered, making the overall feel of the object more stable.
Especially in celadon, this phenomenon can even be said to be of the same origin.
It is recorded in the "History of Chinese Ceramics" written by Ye Zhemin that the phenomenon of gathering foam and beads, like stars, can be observed in the porcelain pieces of Yue kiln.
Its internal bubble distribution is very similar to that of Ru kiln in the Northern Song Dynasty, and it is related to inheritance.
In monochromatic glazes, unlike other decorative glazes, the surface can be decorated by painting, engraving or piling up sculptures.
The single-color glaze has higher requirements for the luster, fullness and layering of the glaze color.
Therefore, Jumo Cuanzhu came into use and was passed down.
In addition, collecting foam and collecting beads is also of great significance in antique appraisal.
When porcelain was fired in ancient times, the environment, firing materials, etc. were all different from today.
Moreover, different periods have different characteristics, which will produce different states of bubble distribution with certain characteristics.