Article reprinted from Earth Magazine
Pots, as we all know, are a kind of kitchenware.
The pots used in daily homes are mostly made of iron, copper, aluminum alloy and stainless steel.
In addition to these, there is another category, that is, the stone pot, the stone pot mentioned here is a pot made of pure stone, excluding the casserole made of stone.
As early as the Stone Age, ancient humans began to use stone as a pot, in addition to stone pots, other containers, cooking utensils, soup spoons are also made of local materials. At that time, when humans went out hunting, they only needed to bring a bag of salt and use simple ingredients to cook a delicious dish.
Ancient Chinese humans used stone tool scenes to simulate wax figures
In the middle of winter, most parts of the northern part of the continent have already received snowfall, so let's take this opportunity to get to know the popular stone pot in the winter.
1
What are the conditions required for the raw materials used to make stone pots?
The earth's surface is distributed with a variety of rocks, which can be divided into sedimentary rocks, magmatic rocks and metamorphic rocks according to their genesis. Among the three major types of rocks, not all rocks are suitable for raw materials for stone pots, which are closely related to the type of rock itself, mineral composition, particle size, structural structure and other properties.
Dali rock has a beautiful texture
But not suitable for making stone pots
Common stone pot shapes are cylindrical, broad-bottomed and spherical, which requires the rock used as a raw material to be blocky or thick. Conversely, thin layers of rock cannot meet this condition, such as thin layers of mudstone, sandstone, slate, etc.
Rocks with large and uneven sizes and uneven distribution of mineral particles cannot become raw materials for making stone pots, and coarse particles are not only not easy to carve, but also easy to form weak bands in contact with large and small particles, which are easy to crack when heated.
Several shapes of stone pots
Loose rocks are not suitable for stone pots
In addition, the raw materials for the manufacture of stone pots also require the main constituent minerals in their rocks to have the characteristics of high temperature resistance, easy heat conductivity, relatively soft texture, and no harmful elements.
There are currently two common types of stone pots on the market.
One is the Korean stone pot, which is made of granite;
The other is the Ink Stone Pot, which is made of the local serpentine talc schist of The Ink.
The granite stone pot used for Korean bibimbap generally lasts about half a year, but in contrast, the ink stone pot is very durable. The same stone pot, why is the difference so great?
2
Korean-style stone pot
If you have experienced eating Korean bibimbap, you will find that the bottom of some stone pots is cracked, and a closer look reveals that these cracks are created along the contact site between the mineral particles, so what causes it to crack?
Granite is an important part of the Earth's continental crust and is an important marker that distinguishes Earth from other planets in the solar system.
Some scholars have done detailed research on the changes of granite after heating, and call this rupture thermal rupture, which is mainly caused by changes in temperature.
Mineral particles within granite (quartz, feldspar, etc.) due to the difference in thermal expansion and cold contraction, resulting in thermal stress between mineral particles, resulting in thermal rupture.
Heat-resistant stone pot
According to the temperature mode of action, it can be divided into two types: the heat expansion and deformation of the rock during the heating process, and the shrinkage deformation of the rock during the cooling process. It should be emphasized that the thermal rupture of rocks during cooling is not an inverse process of thermal rupture of heating.
The mode of action of different temperatures will have a great impact on the thermal stress distribution inside the rock, and the thermal fracture mechanism is different, the degree of deterioration is different, and its mechanical properties will be very different. During the cooling process, the frequency and intensity of thermal rupture are higher than those of the heating process, and the thermal damage is also stronger than that of the heating process.
The experimental results of the thermal rupture acoustic emission characteristics show that in the range of 600 °C, the thermal rupture of the heating process mainly occurs above 300 °C, especially above 460 °C, which is more intense, and the elastoplastic thermal rupture mainly occurs. In the process of cooling, thermal rupture mainly occurs in the temperature section of 300~100 °C, and brittle thermal rupture mainly occurs. Brittle thermal cracking is the most important reason for the rupture of Korean stone pots, which will generally be replaced by a new batch in half a year, fortunately, the granite is widely distributed and the cost is relatively cheap.
A granite rock pot with cracked bottoms
3
Ink stone pot
As the county seat of the country's ultimatum highway, Metuo has always been known as difficult and closed, where every mountain, water, stone and tree are shrouded in mysterious colors. I believe that all those who have visited Metuo will describe their physical and mental feelings in their own unique way, describe its beauty and hardships, and depict its unworldliness and hardship.
La Snow Mountain, Methikalon
The ink stone pot is very special, which is mainly related to its special raw materials. The mothstone pot is made from a rock called serpentine talc schist, which is distributed intermittently along the Great Bend of the Brahmaputra River and has special geological significance.
During the northward subduction of the Indian Plate and the collision with the Eurasian Plate, the rock is formed by the alteration of the supermassive rock representing the oceanic crust, in other words, the rock is a rock with a special memory, which records the evolutionary history of the collision of the Eurasian Plate with the Indian Plate and the formation of the Qinghai-Tibet Plateau.
Raw materials for ink stone pot (marker pen is scale)
Serpentine talc schist is mainly composed of talc, mica and amphibolite and other minerals, mostly fibrous, flaky, soft texture, easy for local craftsmen to carve by hand; and can withstand 2000 ° C high temperature, the surface is silky, if lucky, you can also see a certain degree of local development of jadeization.
It is these characteristics that have created the unique charm of the ink stone pot, and the ordinary household ink stone pot can be used for a long time, as short as decades, and as long as several generations.
Coupled with the geographical conditions of the production area of the ink and the limited raw materials, the ink stone pot is more expensive than the general stone pot.
Regardless of the material, the rock used to make the stone pot must have the following characteristics: blocky, dense, high temperature resistance, good toughness, easy heat conductivity, easy carving, and can not contain harmful substances.
When you cook in the kitchen with stone pots, when you eat bibimbap in stone pots, do you have a new understanding of the "unpretentious" stone pots, which may have a geological lifespan of hundreds of millions of years. It bears witness to the vicissitudes of the earth and also carries our love for a better life.
END
Editor-in-charge | Winnie
Typography | Winnie
Audit | Liu Dan
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