Gotscha is Georgian but he lives in Rosendaal in the Netherlands (not very far from Antwerp in Belgium).
He studied the Bulat technology with his friend Zaqro in Tsibili, and so we had an overload of questions for him, concerning the history and technology of the Bulat.
After lot's of communication with Gotscha, the idea of getting Zaqro to Belgium and make it in to a Bulat-worshop rose, so last weekend (20-21/11) the workshop was helt.
A total of 20 interested persons took part of the workshop.
Afterwards Zaqro was asked if he was OK with us further exploring and communicating about his technique, since he had been testing all kinds of Bulat making for the last several years (and over 800 smelts) to get where he is today. He shared our opinion that evolution can not come out of keeping secrets and he was fine with us sharing his technique, as long as we told everyone this was the Georgian way.
So here it is, the Georgian way of making Bulat, AKA Wootz, Crucible steel.
Zaqro makes the crucibles himself out of :
(parts are volume-parts)
7 parts Grog(crushed fireproof brick)
3 parts cokes
2 parts kaoline (China clay)
1 part fireproof clay (common white clay)
Every ingrediënt is crushed to dust-sized particles
Water is added so that it sticks togheter when squeezed, but falls apart when you try to break it.
This is compressed tightly in a mould, and afterwards pushed out.
The crucible is filled.
Zaqro prefers pure ferritic Iron, thus we used ARMCO plate, which we cut into small squares (10X10mm). Normal welding electrodes are also good to use.
He takes about 300g of iron to fill his crucible, which he divides in to two equal parts.
One part is put in the crucible at the bottom. on top of this, he puts a layer of sand. this sand comes from a georgian river, but every sand or glass that melts at around 1100°C will do the trick.
On top of this sand he puts a layer of charcoal of about 10mm thick.
That he punt on half of the remaining part of Iron. On top of this, he puts another part of charcoal. on top of this he puts the last part of Iron, and on top of that he puts another part of charcoal.
He also added some manganese to 'calm down' the melt.
This is a copy of a drawing by Seerp, for the charge of the crucible.
The lid of the crucible is made by mixing the leftover Kaoline and clay to form a pancake which is carefully placed on top of the crucible. Zaqro makes a hole of about 8mm in this lid.
The crucible is put into an oven, made on top of the forge by fireproof bricks. the crucible is placed on a piece of brick on the bottem of the oven, and is relativly slow heated with charcoal.
When there is a good fire going on at the bottom of the oven, cokes or antracite is added (not too much) to the oven. when the entire crucible is surrounded by glowing cole, the time is noted and the entire oven is filled with cole.
Photo of oven when the time was noted.
Now the oven is run for about an hour. afther this hour the wind of the forge is shut down, and the crucible is left to cool inside the glowing cole.
It is best to let the oven cool down entirely before removal of the crucible, but at the workshop the crucible was removed after about 1 hour.
the result inside the crucible is remarkable: At the bottom an ingot is found. on top of this ingot there is a layer of glass, from the sand. on top of this glass there is leftover charcoal.
What happened inside the crucible is as follows: The upper part of the charge (on top of the sand that is) has carburised to form cast iron. Meanwhile, the sand has been molten and gotten into the pure iron at the bottom of the crucible. The cast iron with about 3% of carbon in it melts between this pure iron at the bottom, pushing the glass back to the top of the steely mass, preventing any acces carbon to diffuse into the liquid.
So this type of charge gets itself carburized to about 1,5% automaticly. By using other lengths of firing Zaqro said he could influence the carbon content of the ingot.
the as-cast ingot:
When the ingot is cooled, zaqro heats it up to about 1150°C. at this stage, the leftover glass on top of the ingot is acting like 'champagne bubbles', when he listens very carefuly he can hear it making 'the sound of a little snake'. this glowing procedure takes about half an hour.
He leaves the ingot on the anvil to cool it down to an orange heat, and he forges the first time.
At first he strikes the ingot with just a few blows, and never turns the ingot while forging, only to turn it when he makes another heat-cycling.
He never goes under 800, and never over a 1000°C when forging, and uses for about 65 heats to forge a knifeblank.
He did three melts which were all succesful. He forged two of the ingots out, resulting in 3 knives with a very nice pattern, and one piece of Bulat (roughly 60X20X8mm) ready to be forged into a knife.
One knife, complete with making the crucible, melting, forging and hardening but still to be finished by grinding takes him about 7 hours.
more pics will folow!
Edited by Klaas remmen, 22 November 2010 - 10:57 AM.