Is it different from just a crack? What is "penetration"?

Is it different from just a crack? What is "penetration"? - cover

Ladies and gentlemen, have you ever seen a crack pattern in a vessel?
Actually, this is not just a crack, but a phenomenon called "penetration".
It is pronounced as "kannyu".

Kannyu has been enjoyed as one of the highlights of pottery since ancient times.
If you know how it works and how to interact with it, choosing a vessel will be more fun.

Why is penetration possible?

Kinyu is the crack pattern on the surface of the glaze.
It is caused by the difference in expansion/contraction rate between the substrate and the glaze.

That's a simple explanation, but you don't know what it's all about with difficult words.
Let me explain in a little more detail.

Materials have the property of expanding when heated and contracting when cooled. This is called "thermal expansion".

In addition, ceramics are not finished just by shaping the clay, but are fired after applying a glass-like substance called "glaze" to the original clay called "base".
This makes it possible to express colors other than the earth color and prevent the juice of the dish from seeping into the vessel.

"Clay" and "glaze", which are the raw materials of pottery, have different expansion and contraction rates due to heat.
Then what happens when the fired pottery is taken out of the kiln?

When the pottery comes out of the kiln, it is exposed to the open air and the temperature drops rapidly.
At this time, the base material and the glaze shrink due to the reaction of thermal expansion, but basically the glaze shrinks more than the clay.
Since the substrate and the glaze are in close contact, cracks (=penetration) appear on the surface of the glaze, which shrinks further. This is what is meant by “penetration”.

Even if intrusion occurs due to aging

Depending on the artist, it is considered to be one of the expressions of the vessel by aiming for this intrusion.
On the other hand, intrusion may occur while using it at home.

In this case, the bowl is warmed by the hot food being served, and then cooled down, causing the same phenomenon as when the bowl is taken out of the kiln.

In addition, it does not penetrate any vessel, and it changes depending on the type of soil and glaze.
Furthermore, even if the clay is the same, the glaze is the same, and the pottery is fired in the same kiln, depending on the position in the kiln and subtle differences in temperature, it may or may not penetrate.

Even if it's a gas kiln instead of a wood-fired kiln, people can't completely control the natural things such as soil and flames.

However, there are expressions that come about because people cannot control them, and that is one of the joys of pottery.
Isn't it a charm that industrial products don't have?

N400 rim plate

At first glance, you can see the penetration of this matte plate. ( N▶︎400 rim plate 6 sun )

Intrusion can be prevented

Penetration is enjoyed as a kind of expression.
I also love crunchy stuff, and I have a lot of them in my cupboard.

However, depending on the case, there are also cases where a negative evaluation (so-called B product) is made if there is intrusion.
This is the case when used in high-end restaurants, or as industrial vessels where exactly the same quality is preferred.

In such cases, preventative measures are taken to prevent intrusion.
He explained that penetration is caused by the difference in expansion/contraction rates between the substrate and the glaze.

Conversely, if the shrinkage rate of the substrate and the glaze can be made the same, no penetration will occur. (Theoretically only)
Thanks to advances in technology, it is now possible to use materials with almost the same shrinkage ratio. As a result, the uniformity of the vessels lined up in major grocery stores is maintained.

white tableware

If you are concerned about it, take care of it

Kinyu means "a pattern of cracks on the surface of the glaze". In other words, it is easier for cooking juices to permeate than non-penetrated ones.

Including such stains due to long-term use, it can be said that you can "enjoy living with your favorite tableware", but I think there are still a certain number of people who are worried about it.

For those of you who are like that, I will also describe how to take care of it at the end.
(Please note that due to the nature of pottery, it will change over time even if you take care of it.)

◇Before using a new instrument

Before using a new vessel, you can delay the aging of the vessel by doing the work of "filling".
(This is not necessary for porcelain. Also, the maker may have applied a water-repellent finish, so please ask the store where you purchased it or the maker for details.)

  1. Prepare the water used to wash the rice, or dissolve flour or potato starch in water.
    (If using wheat flour or potato starch, add 1-2 tablespoons to 1 liter of water and use it as a substitute for the water.)
  2. Put the rice water and the bowl in a pot that is large enough to completely submerge the bowl. (If the container is too big to fit in the pot, pour the washing water from 4 below into a well-dried container to seal it.)
  3. Add a handful of rice if you want to make it more solid.
  4. Bring to a boil over low to medium heat. (Be sure to put the container in room temperature water and then slowly heat it over low to medium heat.Putting the container in a boiling pot or heating it rapidly over high heat may cause damage.)
  5. After boiling for a while, turn off the heat. Wait until the pot is completely cooled, remove the pot, wash it and dry it well. (I turn off the fire about 12 to 15 minutes after lighting it.)
How to close your eyes

◇ Before daily use

Each time you use it, soak it in water to absorb the water before using it.

in conclusion

Some of our dishes also have crazes, so this time I tried to summarize the mechanism.
I would be very happy if the questions of those who were wondering, "What is this crack pattern?"