At three o'clock the next day, Su Yuan got up, basically returned to normal, took a hot bath, woke up Xu Kui, and began to eat.

"What are we going to do today?" "Emi Yanagi watched Su Yuan finish the breakfast she had carefully prepared, and asked curiously, "One more day off?"

Su Yuan shook his head and said with a smile: "Strike while the iron is hot, you rest today, I want to open the sword spine!"

Xu Kui and Emi Yanagi glanced at each other, and began to get excited again, after yesterday's personal experience, he had seen Su Yuan's unfathomable sword casting level, rest?

What a waste of life!

Su Yuan ate and drank to his heart's content, came to the backyard, took out the sword embryo, and observed carefully, although his eyes were full of golden light, they were a little scattered, as if they were running around without a head or a brain.

"It should be the reason why the sword spine is not opened!"

A thought flashed through Su Yuan's mind, the so-called sword spine is the backbone of the sword, which has the effect of enhancing the strength of the sword body, and can also adjust the weight distribution of the sword body to make it even.

There are single, double, or triple ridges, so the sword is also divided into four-sided swords, six-sided swords, and eight-sided swords. The spine of the sword is required to be straight and the blades on both sides are symmetrical to maintain the balance of the sword, and the most difficult thing to grasp is the polishing of the spine.

During the Han and Tang dynasties, steel swords basically replaced bronze swords, and knives on the battlefield gradually replaced swords; steel swords mostly adopted forging technology, and the style of swords mostly inherited from the Eastern Zhou Dynasty to the pre-Qin bronze swords, with a long and narrow blade body, and a flat stem and folded shoulder. Only the sword ridge is different, the sword ridge is slightly thicker. In the early Han period, the sword was mostly eight-sided and six-sided, and in the middle period, the sword flower was four-sided with small convex edges.

In the later period of development, the shape of the sword spine was more concise, and the swords of the Ming and Qing dynasties were mostly ridges and round ridges, and many of them would open single or double blood grooves on the sword body to increase the lethality.

Generally speaking, thick-ridged swords are mostly cut close to the edge of the sword body to enhance the firmness of the sword, while thin-ridged swords are mostly sharpened directly from the spine to the edge of the sword body to improve the cutting performance of the sword body.

It is like the backbone of a human being, holding up the weight of the whole body, standing upright, proudly between heaven and earth.

"These are freshly delivered stones, and I use them a lot to polish. "Emi Yanagi took out a large bag of black stones that had been airlifted in the air, boxy and delicate and smooth to the touch.

Su Yuan took it, scattered the water on it, was absorbed in an instant, and nodded secretly, it is worthy of a high-end goods worth two thousand dollars, a whetstone for local tyrants.

Listening to the introduction of Emi Yanagi, the sword casting status in the island country is high, and an industrial chain has been formed, from the initial iron ore collection to the final scabbard decoration, there are special masters in charge, and the top works are worth a lot.

In the "Ensho Shiki", a book that recorded the rituals and systems of the palace in the early Heian Dynasty, the method of making the Togaku horizontal knife is described, and you can see the general form of the grinding process at that time, such as deer grinding, firing and middle grinding, fine grinding, and Ying.

Regarding these processes, the swordsmith at the end of the shogunate, Mizukoko Masahide, explained in his book "The Secret Biography of Sword Work" that the deer is a barren stone, and the burning and grinding are equivalent to the common temples and other stones, and the latter two have no corresponding processes in the modern grinding process, which is roughly equivalent to the middle part of the Shijoken.

"Holistic grinding is a secret, a skill that only a true master can master. Emi Yanagi explains, "In particular, this step causes the blade to glow a color like a cloudless clear sky in autumn, and the muscles to glow blue-black. ”

"This is the legendary blue and black, representing the way of heaven and earth, yin and yang, and it is a supreme treasure!"

After speaking, he picked up a piece of stone and said: "Master, please see, this is a vajra, coarse grain, used for a large area of rusty swords." ”

"This is a water preparation tomoto, produced in the Amakusa region of Kumamoto Prefecture, the color is yellow and white, the fineness is about 400, the stone is medium-hard, and the cutting ability is medium. ”

"Yamagata Prefecture produces corrected ton, brown, fineness of about 600, hard stone, medium cutting capacity. ”

"Minami-Shiraku-gun, Aichi Prefecture produces a medium-sized Kurato, yellow and white mixed in color, fineness of 800-1200, hard stone, and medium cutting capacity. ”

"There is also a chikuto, cut from Narutaki from the Kyoto region, yellow and gray-green, with a hard texture, and it is a special ...... for sharpening knives."

Xu Kui looked at seven or eight kinds of stones, scratched his head and said, "You guys are hypocritical, it's so troublesome to sharpen a knife?"

Liu Shenghui glanced at him stupidly, and said dissatisfiedly: "This is a sacred thing, of course it must be taken seriously, if it weren't for the time being too tight, I would like to fly back to China and find the best ...... for the master himself."

Su Yuan waved his hand, looked at it once, it was basically enough, and asked curiously: "How do you polish it?"

Emi Yanagi quickly stood up, took out a complete set of tools, knelt down directly, and demonstrated: "First put the stone on the thick wooden block, the wooden block has a groove that can block the stone from sliding." ”

The grinder takes a kneeling position and presses the stone with his left foot on the bent log. The thick wood blocks are inclined at 35 degrees, and the grinding is only half of the stone. In this way, the stone is changed back and forth, and the middle will not be recessed, which is also one of the criteria for evaluating a grinder's skills. ”

"Sword grinding can be divided into the ground grinding and the upper grinding, the lower ground grinding is the basic shaping and grinding of the sword with a stone, and the upper grinding is the fine grinding of the sword, so as to further beautify the process of the blade. ”

"The best master is the ancestor of the Honami family, Myo, a thousand-year-old craft that has been passed down from the Northern and Southern Dynasties era, and the family has served the Ashikaga family, the Toyotomi family, and the Tokugawa family for generations, and has carried out katana grinding and appraisal work, and now it is the most famous Honami Mitsuyue. ”

Emi Yagyu took out a katana and demonstrated it attentively, first polishing the blade with a Vajra sword, about 180-220 meshes. Then it is necessary to prepare the water and grind it into the shape of the blade, 400-600 mesh.

In turn, use the correction to the spine (900 mesh), the middle name Kurato (1200 mesh), and the thin name Kurato (1500 mesh) to grind coarsely.

Finally, there is the Uchizuto, which is famous, and is divided into blades and grounds, which are sharpened separately. It is a natural stone produced near Kyoto, and it can show changes in the texture of the earth and subtle texture, about 4,000-6,000 mesh.

"It's Blade Yan!" Emi Yagyu pressed a small piece of Uchizumi with her fingers and grinded it on the blade until it felt smooth. Explains: "Then use about 10-20 pieces of Narutaki, cut into small pieces and rub them with your fingers, so that the subtle changes of the knife can be revealed. ”

"Wipe the oxide scale powder that appears in the forging process of the knife and oil to make a black paste, and wipe it back and forth on the knife body with cotton. The fine powder will seep into the blade, and the knife will show a black and shiny luster. And the earth muscles will become clear......"

Finally, the stone used in the blade process is cut into round slices, and the blade lines are wiped and the blade lines appear. The whitish part of the blade pattern seen from the side shows the personality and characteristics of the sharpener in this process......

After a whole set of processes, Xu Kui was dumbfounded, thinking that he only used a few stones to polish each time, and secretly picked his thumb: worthy of being a little devil.

What a pervert!