【Introduction to Traditional Crafts】 ～Sakai forged blades (Osaka Prefecture)～
2022.12.22 About Japan's Traditional Crafts
Sakai forged blades
【Production area of Sakai forged blades】
Sakai City, Osaka City, etc. in Osaka Prefecture
【What is Sakai forged blades?】
Forged blades made in areas centered around Sakai City and Osaka City in Osaka Prefecture.
By using two different materials, “base metal (metal that is easy to process)” and “hagane (metal used for the edge of the blade),” the craftsmen are able to achieve not only durability but also sharpness at the same time.
In March 1982, it was designated as a traditional craft.
【Features of Sakai forged blades】
There are mainly two features.
①Sharpness of cutting edge
It can be said that the outstanding sharpness of the cutting edge is the result of the technology of “forging” and “sharpening” by craftsmen with outstanding skills.
A method that is becoming more common in kitchen knife production these days is to hollow out the iron plate and shave the blade to make it into a kitchen knife.
Sakai forged blades, on the other hand, are very different in that they are shaped by striking two types of metal that are glued together.
Knives forged with techniques cultivated over many years are hard and sturdy, and retain their sharpness for a long time.
②Division of labor in the manufacturing process
There are three major processes to complete a blade: blacksmithing, sharpening, and attaching the handle.
There are specialized craftsmen in each process, and it is possible to make high-quality Sakai forged blades by performing the work with their skilled skills.
Sakai forged blades come in a wide variety of shapes so that they can be easily used according to the type of ingredients and dishes.
From what I have told you so far, you can probably understand why Sakai forged blades is highly favored by chefs and chefs.
【History of Sakai forged blades】
It is said that the technique of making Sakai forged blades is based on tools such as hoes and plows that were used when building ancient tombs.
In Sakai City, there are many ancient tombs that are thought to have been built during the Kofun period, including the tomb of Emperor Nintoku (the largest keyhole-shaped ancient tomb in Japan).
Civil engineering work was frequently carried out to build ancient tombs, and tools played an important role during that time.
Craftsmen began to settle in Sakai to manufacture a large number of tools, and it is assumed that the manufacturing techniques for not only tools but also swords and other items evolved.
In 1543, guns were introduced to Japan (Tanegashima), and guns spread throughout Japan in an instant.
Production of guns began in Sakai, where there were many craftsmen with advanced metalworking skills.
In the latter half of the Sengoku period, matchlock guns began to be used as new war weapons, and Sakai played an important role as one of the major production areas.
Sakai faces the sea, making it easy to import raw materials for gunpowder, and is said to have produced 100,000 guns by the Edo period.
In the Edo period, the need for firearms decreased, but cigarettes began to become popular instead.
And the demand for “tobacco knives” for chopping tobacco leaves increased.
The high-quality tobacco knives made by craftsmen living in Sakai earned a good reputation.
Then, the shogunate put a hallmark of “Sakai Kiwami” on it and started selling it nationwide as a monopoly of the shogunate.
With the recognition of the Tokugawa Shogunate, the name of Sakai knives became known throughout the country.
Due to modernization, tobacco production has been mechanized, and the demand for tobacco knives has declined significantly.
However, the craftsmen started making kitchen knives and other items for use in cooking, making use of the techniques that have been passed down over the years.
Sturdy and sharp Sakai forged blades are highly praised by chefs and chefs, and are still used by many people today.
【Production process of Sakai forged blades】
①Attaching blade metal
Follow the steps below to make the iron plate that will be the material for the forged blades.
・The base metal is heated red, and it is layered with the blade metal with powder such as boric acid and iron oxide.
・Put it in a furnace with a temperature of about 900°C to soften it.
・Hold the two pieces of metal together by hitting them with a hammer.
Workers will do the following:
・Put the iron plate in the furnace again and heat it to 600-700℃.
・Hit the iron plate with a hammer to spread it out thinly.
・By tapping, the two metals are blended together and shaped into a knife.
・Cut off unnecessary parts and shape the part that will be inserted into the handle.
After the shaping is completed, the knife is placed in the straw and gradually cooled in a natural way.
By going through this process, the strain inside the knife can be removed.
“Ara-tataki” is the work of hitting the surface of the kitchen knife that has returned to room temperature with a hammer.
It has three main effects.
・Unevenness and holes made in the previous processes can be flattened.
・Because unnecessary ingredients are knocked out, the kitchen knife is forged.
・Eliminate distortion by making the thickness of the knife uniform.
The unnecessary parts are cut off according to the shape of the knife to be made.
・Adjust the distortion and twist that came out by trimming, and scrape off unnecessary parts.
・Use a grinder (a machine that can grind and shave) to finish the whole.
・Make a stamp on the back of the knife.
・After removing the dirt and oil on the knife, apply mud.
・After painting, use residual heat from the furnace to dry.
The purpose of applying mud is to achieve the following two effects.
・Baking unevenness can be suppressed.
・ After quenching, it can be cooled uniformly in a short time.
“Quenching” is the process of heating to a temperature of 750-800°C and then immersing it in water to cool it all at once.
Rapid cooling changes the composition of the blade metal and increases its hardness.
The next step, “tempering,” is to reheat the quenched blade to 180-200°C and then cool it down naturally.
By performing this “quenching” and “tempering”, the blade metal becomes sticky and the blade is less likely to chip.
Both operations are performed within a defined range of temperatures, but without a thermometer.
The craftsman drops water on the knife and checks the temperature by the way the water droplets flow.
This is a work that requires the excellent skills of craftsmen, such as experience and technology.
The craftsmen go through the order of “rough sharpening → fine sharpening → back sharpening → blurring → finishing”.
To determine the angle of the blade, as the name suggests, the blade is roughly sharpened.
Check frequently to see if the knife is distorted.
While carefully polishing the scratches and distortions caused by rough sharpening, the thickness of the blade is also adjusted.
The work of sharpening the back side of the blade while gradually making the grain of the whetstone finer.
As with the work up to this point, the craftsmen are checking to make sure there are no scratches or distortions.
The work of rubbing the blade with a slurry made by kneading whetstone powder.
While the base metal part becomes cloudy, the blade metal part becomes glossy and shines.
As a result, the blade crest (the boundary between two metals) stands out clearly, and the appearance changes beautifully.
The blade of the knife is carefully sharpened with a very fine whetstone to create a sharp knife.