They started to build the tatara on Saturday the 12th and finished it by Wednesday the 16th (so you thought you could build that in a single afternoon ).

The original tatara, as you can find them in Japan are 3m long and 1m wide but since they only had 1 week time to build and operate it, they scaled it down to 1.30m long, 1m wide and 1.3m high.

Here you can see the charcoal they gathered to keep the furnace going :

This is how 3700Kg charcoal looks like

16 Big bags with a weight of 200-250kg each. So if we take our calculator, that’s around 3700kg total. At the end , they have been using ‘only’ 3000kg of it. This charcoal was made of pinewood in a traditional way. These are not the same as the charcoal we use to have a barbecue party.

That kind of charcoal is too heavy, can’t reach the high temperatures they need and is glowing too long.

The iron ore that has been used, Sishen (coming from South Africa), is exact the same as the Japanese satetsu when looking at the chemical components within it . The difference here is that the japanese satetsu is black and the Sishen obviously not. They had round 2000kg of ore but ‘only’ 1300 kgs has been used during this process.

Sishen iron ore

And off we go, they digged a pit, 25cm deep and light a fire to make it completely dry.

Making a first fire to get the pit dry

The pit is filled with small pieces of charcoal

pit filled with charcoal

Basic construction : to build the furnace, they used 250 fireproof stones, 500 Kg clay and 700 Kg sand (quarz).

top view

Bottom part of the furnace

Pavel is finishing the bottom part with clay

Done

The finished furnace, ready to go...

Thursday 17th, 9.00h…Katja Lohmaan-Hütte, owner of Lohmaan-Stahl, is activating the furnace.

Let it burn..

Pavel checking the vents

Time for a first check

The First slag is coming out after 17 hours

Slag coming out

During the second night (Friday to Saturday) there was “a sea of magma”

Magma

Saturday 12h, letting the slag out for a last time

Almost there

Saturday 13h, filing the furnace for a last time with ore

Filling the furnace with ore for the last time

Saturday 15.30h, starting to take the tatara apart. At first sight it didn’t look like a lot of steel was produced

Taking the tatara down

Hey…they did find a little piece of steel

The first piece tamahagane

With 1300Kg ore being used, the little piece was only a fraction of what was coming…The next piece they found was a ‘bit’ bigger and too heavy to get it out by hand so they had to use other equipment…

Time to get some help to lift the big chunks

There were 2 big blooms produced, one of 180Kg and another one weighting around 210Kg. Besides that they did found another 25-30kg in the furnace and after cooling down there was 20-25kg cast iron found at the bottom of the tatara.

The biggest blooms were taken to the forge, where a 1500kg (air) hammer was used to make smaller pieces out of the big chunks.

The 1500 kg air hammer

The tamahagane that has been produced was of an excellent quality. No slag, very little wholes and big grains.

After building the furnace (12hours/day) and working 55hours straight to operate the furnace (every 10-15 minutes adding 10Kg charcoal and 7Kg ore) they finally had what they were looking for…real tamahagane..

The very idea of working alone, at peace, retired in a workshop set in the countryside, nearby a fire, with steel only for raw material, doing a work that never ceases to bring renewal and wonder, delighted him very much and In December 2005 he decided to chase his dreams and took of to Japan to start his Smith apprenticeship.

Now, anno 2009, he is still living and studying there and his aim is to become a licensed (westerner) swordsmith in Japan.
To quote Pierre :

“I’m at this point where I have touched everything, tried every technique but haven’t mastered anything! It’s very challenging and stimulating at the same time.”

I’m not sure about you but I’m very curious in such a way of living and Pierre is willing to accept questions and doing an interview..so…
Wondering how it is to chase an living your dream, this is your chance !!

Put your questions (regarding Japanese Swords) in the comment box below, or in the box on the right side of  this video and we make sure they got included in the interview. If there’s enough interest, we might plan to do some other things as well

So what would you like to ask to PIERRE ?

In the tatara, it is the burning charcoal that supplies the carbon. These typical Japanese smelter is made of clay, about 5 feet wide, 48 inches tall and 15 feet long, where it’s walls are 10 inches thick.

One operating cycle of the tatara takes 5 days. One day to build the walls (clay and sand), 3 day’s to smelt and 1 day to remove the iron out of the tatara. In this 5 days process , they need about 13 tons of charcoal and 8 tons of satetsu (black sand) to produce 2 tons of iron and steel, which is called Kera.

About half of this Kera is composed of steel ranging from 0.6 to 1.5% carbon and it is this portion that is called tamahagane. Only Two thirds of the tamahagane is of a good quality. The rest of the Kera can be used for forging swords if another separated forging operation is done, this process is called Oroshigane, where carbon is added or reduced.

Every time Tamahagane need to be made, the tatra needs to be rebuild. Its walls must be build out of clay bricks. The mixture that is used to make the bricks does contain a large amount of sand (silicon oxide) which makes the tatra resistant to fire and melting.

Since the forging process of a sword produces a continues loss of carbon, most of the smiths like to start with tamahagane that has an carbon content of 1.0 to 1.5% to forge the kawagane (jacket steel).

A billet of tamahagane t from the tatara furnace is very big (as you can see in the video) and includes various qualities of steel. The big ‘rock’ of Tamahagane is broken into many small pieces to check the quality.

From here on the smith can choose the right pieces and start the forging process of this katana.

This very nice video is showing the process of making Tamahagane

Once the blade reached the 750-800°C, the structure of steel changes to austenite. Now, when the blade is quickly cooled by quenching (in water), austenite changes to martensite, the hardest type of steel. However, because of the clay application, the blade will cool more slowly where the clay is thick (on the back of the blade), turning not into martensite but instead forming ferrite and pearlite, which are softer and more flexible. So as result, you will get martensite on the edge and ferrite & pearlite on the back which gives the sword a ‘flexible construction’.

This hardening process also creates a visible change in the surface of the metal. It mainly depends on how the clay mixture was applied, but variety of effects can be produced and seen without looking ‘inside’ the blade. This pattern is called the hamon, and is one of the most important aspects in the aesthetic appearance of the Japanese sword. Like the jihada ( the surface pattern of the blade ), each of these hamon patterns has a specific name. Sugu, for example, is a very straight hamon, Gunome a zigzag pattern, Notare a wave pattern,etc.

Once the blade is successfully hardenend ( and in most cases, 50% or more of the blades are failing and does show cracks along the blade ) it’s not totally done. In most of the info your read, they talk about the forging, the hardening and that they continue with the polishing, mounting, etc but they all forget 1 important step, the tempering of the blade.

During the tempering process, the blade is heated again but this time to a much lower temperature and re-quenched. Since the temperature is far below the critical temperature (that is needed to harden the blade and change the structure of the steel), it won’t change the molecular structure of the steel anymore . Instead, it will simply help to relieve any internal stresses which the hardening process have built up.

The hardening process of the blade is in one of the most important and perhaps the most difficult part of the  sword making process. It is the correct hardening of the Japanese sword that gives the blade its ability to take and retain an amazing sharpness.

After the blade is forged and finished to it’s final (raw) shape, the differential hardening process can begin. To start with, the blade is being coated in a mixture (also know as yakibatsuch in Japanese ) of water, clay, ash, and other ingredients. Every smith has his own and in most cases, a ‘secret’ special recipe. The clay mixture is applied over the surface, thicker along the ‘mune’ (or spine) and thinner at the ‘ha’ (edge). In other words, the clay mixture will act as an insulating “blanket” during the quenching process. Allowing those areas that are covered by a thicker layer of clay to cool much more slowly.

Once this is done, “ashi” is applied to the clay coat. Ashi are the thin strips of clay you can see over the whole surface of the blade on this picture. These stripes are providing some insulating action in the quench as well, and will form little sections of softer material in the hardened edge. The Ashi are giving the blade the ability to prevent ‘cracks’ in the blade under hard use and lot of pressure. They also contribute to the formation of crystalline features within and around the hamon itself.