My system is not decent

Chapter 1651
After a cultural relic is damaged, there is also a little benefit.

Because of the destroyed cultural relics, it is more convenient to study.

Not afraid of damage again, but it just allows researchers to better perform Song Dynasty kiln wares by looking at the internal performance.

For example, you can look more closely at "Jufozhuanzhu".

The term "gathering foam and collecting pearls" has not yet been found out the exact source.

However, some said it was Song Huizong who said it, and Chen Wenzhe doubted it.

Because to see the small bubbles under the glaze, you need to use a magnifying glass to observe.

In the Song Dynasty more than 1000 years ago, although the technology was quite advanced, there was no cash to have a magnifying glass!

So how did Zhao Ji see this phenomenon?If it is a poly ball, then it is easy to understand.

However, many classic records are about gathering foam and saving pearls!
Mr. Sun Yingzhou mentioned in the book "Appraisal of Yuan, Ming and Qing Porcelain": "The density of Ruguan and Ge's glaze bubbles is like pearls."

What exactly does "gathering foam and collecting pearls" refer to?
In fact, you can "bite the words" here.

Let me talk about "foam" first, which refers to foam.

In Baidu Encyclopedia, bubbles are explained as "many small bubbles gathered together.

Dispersion system formed by dispersing insoluble gas in liquid or molten solid" and then "beads".

That is, many small bubbles are aggregated into large bubbles, which are called "beads".

In the other two verbs, "gather" refers to the state where the bubbles are next to each other and gather together, and the bubble is the state where small bubbles gather;
The word "save" has two pronunciations, one is zǎn, which is regarded as accumulation.

Here Chen Wenzhe believes that it can be understood as bubbles superimposed on each other and gathered together.

Another pronunciation is cuán, which is assembled with ready-made parts, which means that the bubbles will have a series of characteristics.

Through such an analysis, what Jumozhuanzhu is talking about is the air bubbles under the glaze.

The formation of bubbles in the glaze is caused by many factors.

Such as glaze formula, glaze viscosity, firing process and so on.

Generally speaking, there are probably several reasons.

The first is the internal cause, the air bubbles produced by the reaction of the tire glaze itself.

There are many air holes 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 gases escape the glaze layer, two types of glaze defects can occur.

One is that the small air bubbles in the glaze converge into large air bubbles, and the impact on the glaze will form a crater.

If the viscosity of the glaze layer is small, it can return to smoothness.

But sometimes, pinholes also appear.

The other is the discharge of air bubbles, which will produce pits in the glaze.

In addition, as the temperature rises, the glaze layer melts into a liquid phase to wet the green 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.

Gases that do not escape remain in the glaze to form air bubbles.

In addition, the substances contained in the tire decompose at high temperature and cause gas emission.

For example, the crystal water of some minerals will also become gaseous and discharged at high temperature.

For example, some sulfides, nitrides, carbonates, etc. will produce corresponding nitrogen, sulfur dioxide, carbon dioxide and other gases to be discharged.

The specific chemical principles will not be repeated here. Modern people should know everything they have graduated from middle school.

The last reason is that at high temperatures, carbonates break down to release carbon dioxide gas.

After cooling down, carbon dioxide is absorbed and reduced to carbonate, which is a reversible reaction.

The more basic the metal is, the higher its decomposition temperature will be.

Glass solution has the property of dissolving carbon dioxide, but its solubility changes with the change of alkalinity and temperature.

The stronger the alkalinity, the higher the solubility, and the higher the temperature, the lower the solubility.

The alkalinity of glaze is much lower than that of 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 gas in the tire is not easy to discharge.

When the temperature is high, the gas in the tire passes through the glaze surface and produces air bubbles when it is released.

During rapid firing, the gas in the tire and glaze has no time to be discharged, and is sealed by the melted and hardened oil layer, forming air bubbles.

Finally, the effect of temperature on bubble generation.

Feldspar and quartz are often contained in the body and glaze of porcelain.

They account for a large proportion in the formulation system, and 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 disappeared 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 gas phase and glass phase increase.

Small air bubbles move and coalesce due to surface tension.

From small to large, from more to less, and it will rise.

There are even air bubbles that will break through the glaze to be released.

If the viscosity of the glaze is high and the surface tension is small, the depression left by the gas release will not be easily filled, and the flaws of the glaze will appear.

When the temperature reaches 1300°C, the speed of bubble rise and increase slows down.

Under normal circumstances, when the glaze mature temperature is reached, most of the undischarged air bubbles are deep in the glaze layer, at the junction of the tire and glaze, and the volume is relatively small.

So what is the significance of the bubbles produced under the glaze for porcelain?

In fact, the air bubbles in the glaze can be regarded as a flaw in the glaze of porcelain.

It is difficult to avoid during the firing process of porcelain, and even some kiln mouths cannot be avoided.

Even when making ceramics in modern times, how to reduce the defects caused by air bubbles to porcelain will also be considered.

This problem is mainly pitting, depressions, craters, etc.

However, the air bubbles on the glaze are similar to the cracks, turning from blemishes into the pursuit of beauty.

A glaze with air bubbles will eliminate some thieves.

This will produce a certain sense of opacity, making the glazed surface of the porcelain look more oily and full, rich in layers, and making the overall feeling of the utensils more stable.

Especially in celadon, this phenomenon can even be said to be of the same origin.

According to the "History of Chinese Ceramics" written by Ye Zhemin, from the porcelain pieces of Yue kiln, the phenomenon of gathering foam and pearls and Liao Ruoxing can be observed.

The distribution of internal air bubbles is similar to that of Ru Kiln in the Northern Song Dynasty, and it has a relationship of inheritance.

In monochromatic glazes, unlike other decorative glazes, the surface can be decorated by painting, engraving or molding.

The single-color glaze has higher requirements for the luster, fullness and layering of the glaze color.

Therefore, gathering foam and collecting pearls has a place to play, and it has been passed down.

In addition, gathering foam and collecting beads is also of great significance in the identification of antiques.

In ancient times, the environment and materials used for firing porcelain were different from those of today.

Moreover, different periods and characteristics of different periods will produce different states of bubble distribution with certain characteristics.

(End of this chapter)