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Tricks of Smiths
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What is a
trick? |
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When I conceived this module, I
thought it would be large, possibly developing into a
link hub. I
was wrong. The reasons for this are manifold:
- What may appear to be a "trick" to an outsider is just business
as usual for somebody who had invested a lot of time for learning the trade.
No special tricks are required to produce, for example, a
kilij blade with
its complex geometry from a more or less shapeless lump of normal steel. You
just have to keep it at the right temperature and hit it with the right hammer
the right way in the right places for a few thousand times.
- The ancient smiths probably knew some real tricks (e.g. around pattern
welding) that have been lost.
Making a pattern welded sword with a
palmette pattern, for
example, was fairly routine in the 4th century AD in central Europe but would
tax the ken of modern smiths. Maybe it was just hard and time consuming work,
but maybe these old guys knew a trick or two for making palmette forging
easier.
- Things that all smiths do routinely, like fire welding two pieces of iron /
steel, are not all that well
understood scientifically.
So what's the trick here?
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Maybe a better way to address the
topic is to ask what kind of not-so-easy things ancient smiths obviously could
do, and what "tricks" they used to do it. Here is my list:
- Recognizing and sorting different grades of steel / iron
- Faggoting
- Fire welding.
- Dealing with "wootz"
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The first point overlaps with the "tricks of
the smelters and miners" to some extent but I won't go into this
here. |
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Recognizing and Sorting Different Grades of Steel /
Iron |
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A smith had either made the iron /
steel he worked with by himself in a bloomery furnace or he bought it from some
supplier. In the latter case the material may have resulted from three quite
different procedures:
- From a bloom that was worked ("wrought") by some colleagues right
after the smelting or from a in-between smithy that made "half
products" out of bloomery iron / steel.
Here are examples.
- From cast iron that had been fined somehow. In
China that
happened rather early, in Europe the 15th century might be taken as the turning
"point".
- From a crucible that produced ultra-high carbon steel (UHCS) by melting a
mixture of (low carbon) bloomery steel and carbon.
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The
bloomery iron /
steel from the first case always contained
slag inclusions. Moreover, the main alloying element might have been phosphorus
and not carbon. In any case, the distribution of carbon / phosphorous in the
bloom was for almost sure rather non-uniform.
We don't seem to know all that much about the second case. The famed Svedish "Osmund
iron" that, surprise, turned out
to be steel, is a point in case. Anyway, "finery iron / steel" might
still contain slag inclusions from the way it was made, even so the cast iron
it was made from was slag free. It was also likely to be rather inhomogeneous.
The crucible steel
of the third variant was a relatively
useless specialty of India / Central Asia / Persia as far as the normal smith
was concerned. It had some merits for some special products (like sword blades)
but was too hard, too expensive and too difficult to work with for the everyday
things a smith made and maintained.
Let's not forget an old rule: |
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The typical smith worked mostly with wrought iron / mild
steel
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The typical ancient smith was a guy
you knew. He lived and worked not far from you. I would guess that every town
with more than 500 inhabitants had its resident black smith, often with the
additional qualifications as
farrier so he could shoe your
horses. He certainly did not make swords. |
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The "recognizing and sorting" question thus has two
parts. First, how did the normal smith deal with the task and second, what did
the sword smith / specialist do? |
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The answer to the first part is
easy: The normal smith just had his suppliers that provided him with the normal
and most likely local stuff he knew. He might even have been part of the
suppliers when some smelting took place and he participated.
it didn't matter all that much if the quality of his wrought iron / mild steel
fluctuated a bit for most for the products he made. It his wrought iron was not
good, he could tell right away because it behaved wrong. Everybody who can
wield a hammer can tell if a material is soft and ductile, hard and tough, or
perfectly brittle, after all. Somebody who wielded a hammer all the time could
certainly do considerably better. |
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The second part of the questions is
what interests us. Let's first look at the Roman expert (of probably Celtic
decent) who made a complex pattern welded sword around 300 AD from
bloomery steel. He could work a bloom himself but more likely bought the stuff
from somebody else. What he needed was:
- Steel, at best a mild carbon steel for one part of the pattern.
- Phosphorous steel for the other part. Note that two steels with different
carbon concentration will not make a good
pattern.
- Eutectoid or slightly hypereutectoid steel for the edges.
Now consider a Japanese sword smith who made a nihonto from bloomery steel between about 1000 AD and now. He
needed:
- At least two kinds of carbon steel: low carbon and high (hypereutectoid)
carbon.
- Perhaps also medium carbon - but he could make that himself if he had high
and low carbon steel.
Next, let's look at the European sword smith between 800 and 1500 or so who
worked with bloomery steel. What were his
needs?
- Exactly the same as those of the Japanese guy.
What about the European sword smith after, roughly, 1500 AD who worked with
steel fined from cast iron? His needs were
similar to that of the Chinese sword smith since 500 BC or so. He had to rely
on the steel industry to a large amount.
- He bought steel as needed from a reliable source
Finally, we have the Indian / Iranian smith who goes for forging a wootz blade
from crucible steel. His needs are clear:
- He needed a couple of "good" wootz cakes (or bulat eggs). He may
have made the crucible steel himself or, more likely, bought it from a reliable
source.
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What could a smith do to ascertain
that the pieces of steel he made or acquired were the right kind? The range of
tests included:
- General hardness (response to hitting with a hammer).
- Fracture behavior.
- Response to heating and quenching.
- Assessment of fracture surface structure.
- Assessment of "color" (in particular for phosphorous steel).
- Assessing the glowing "stars" flying of a the grinding wheel.
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| Spark test for steel types |
| Source: Internet; unidentified primary
source. |
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I have described some of those tests
in more detail in the
chapter about Japanese
blade forging because we know what Japanese blade smiths did and still do
for testing the quality of their starting material. We can only guess with
respect to all the other ones. |
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Faggoting
and Fire Welding |
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Faggoting involves copious fire
welding so I treat both of these topics in one paragraph.
The need for faggoting bloomery steel results from
- Non-uniform carbon distribution.
- Very non-uniform phosphorus distribution.
- Large extraneous defects like voids, slag inclusions, other
"dirt", in a non-uniform distribution
None of this is acceptable for a high-quality blade. Variations in the
phosphorous concentration, for example, will produce variations of the
contrast, the difference between the bright and the dark part that makes for
the pattern of a pattern welded sword.
Variations of the carbon concentration in piled
all-steel swords defy the
purpose of piling. Large defects like slag inclusions may induce early
fracture. |
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Link
Faggoting illustrated |
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Faggoting is the only
way to overcome these problems. Fold, fire-weld, stretch. Repeat ten times and
you have 1024 layers now. Everything is rather uniform and some large
extraneous defects have been reduced to many small defects. Some might have
been removed (like voids).
So far the smith wouldn't need to resort to tricks, he just has to do his job.
Tricks must come in, however, because faggoting involves copious fire welding
and that is a tricky procedure for several reasons |
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- Fire welding needs high temperatures; not all that easily obtained in early
times,
- Fire welding produces defects of its own like badly welded regions and
oxide inclusions.
- At the high temperature required you always burn off some of your iron /
steel.
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The more you fold and fire weld, the
more uniform your iron / steel will get. But with every folding and welding
less iron / steel is left and the number of welding defects increases. There is
thus an optimum number of foldings that depend on the quality of your starting
material and in particular on your skills as smith. Here your
"tricks" come into play. What do we know about these tricks? |
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Next to nothing. Sprinkling some
"sand" (or flux) on the surfaces to be welded is a well-know trick.
What that might do I have described
elsewhere. Japanese smith
put some rice straw or the ash of rice straw on the surfaces to be welded. What
that is doing I don't know. Since rice straw is rich in SiO2 it
might be just a different way to put flux on the surface.
However, the ancients smiths must have know a trick or two that we have not yet
unraveled. Suffice it to mention the so-called "white weld line" effect
with its mysterious high arsenic concentration.
Only time will tell. So far there are far too few investigations in ancient
(and modern) fire welding techniques and its precise working. |
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Putting rice straw on the steel to be
folded
Nice trick. But what does it do? |
| Source: Internet; unidentified
"forging tamahagane" commercial page |
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© H. Föll (Iron, Steel and Swords script)
With frame
Sword Types