Viking Swords and Wootz

[Jeff Pringle]

Like most newspaper items on esoteric subjects, there is often a bit (sometimes quite a bit ) of error introduced between the interview and the page, so don’t be surprised the facts seem ‘off’ in the Guardian article.
The Viking period spans a few hundred years, and the era includes some pretty radical improvements both in sword design and in steel making, so it would be a mistake to think there was just one way to make a sword during that era. Plus, swords made locally vs. swords made in an ‘industrial’ center & exported will add a layer of difference.

You can get more info on the fake issue and start forming your own theories on which ones were ‘fake’ from reading “The Vlfberht sword blades reevaluated” by Anne Stalsberg, she did a signature analysis of ~135 Ulfberhts, and there are two variants of the signature (the two most numerous) she concludes are probably authentic.

Below is a Williams quote from 2003, when he was starting to develop this concept - note he is saying higher slag content (not quenching!) can lead to brittleness:

Some early medieval swords in the Wallace Collection and elsewhere
David Edge, Alan Williams
Gladius XXIII, 2003 pp. 191-210
http://gladius.revistas.csic.es/inde...rticle/view/50

“….
It should be observed that yet another blade with a similar inscription has been found by one of the authors to consist of a totally different metal. That «Ulfbehrt» sword was made of an air-cooled hypereutectoid steel of around 1.0%C (Williams, 1977). Since that account was published, a great deal more information has become available about the crucible steel industry of Central Asia (e.g. Craddock, 1995 and Feuerbach, 1997) and it seems likely that a cake of such a steel was the raw material for that blade; being virtually slag free and of hardness around 300 VPH, it must have been an exceptionally serviceable sword, and one which would keep its hard edges permanently. The maker of our «Ulfbehrt» sword had made what must have seemed to his customers at the time like a very good copy, with an edge hardness of over 460 VPH. Prolonged use might have altered their opinions; the cutting edge is only 6mm deep, and could have been removed by a few years of regular sharpening on a grindstone. It is also distinctly higher in slag content, and therefore more likely to fracture on impact.
….”

[Gonzalo G]

Jeff, thankyou for your information on this subject, and also on the wootz thread. I found very interesting and useful your comments.
Regards

Gonzalo

[Chris Evans]

Hi Jeff,

Originally Posted by Jeff Pringle

... It is also distinctly higher in slag content, and therefore more likely to fracture on impact.
….”

Informative post.

Without knowing much about Wootz, in wrought iron slag inclusions enhance toughness by acting as a crack arrestor. It is my understanding that the core of Japanese swords is often high in slag content with a similar effect.


Cheers
Chris

[Jeff D]

Originally Posted by Chris Evans

Hi Jeff,



Informative post.

Without knowing much about Wootz, in wrought iron slag inclusions enhance toughness by acting as a crack arrestor. It is my understanding that the core of Japanese swords is often high in slag content with a similar effect.


Cheers
Chris

Hi Chris while awaiting the correct answer from the other Jeff, here is what I think. Slag in well worked steel forms long thin strings "stringers" which will give the effect you mention. In wootz working the steel in a similar fashion would eliminate the watered pattern. Therefore large (unworked) inclusions of slag would provide a fracture line.

Hope I am correct
Jeff

[Chris Evans]

Hi Jeff,

Originally Posted by Jeff D

Hi Chris while awaiting the correct answer from the other Jeff, here is what I think. Slag in well worked steel forms long thin strings "stringers" which will give the effect you mention. In wootz working the steel in a similar fashion would eliminate the watered pattern. Therefore large (unworked) inclusions of slag would provide a fracture line.

Hope I am correct
Jeff

What you say is correct. However, If I read it correctly, that quote about slag was referring not to a Wootz blade, but to a local copy. As such it would have been made from sponge iron and hammered extensively giving rise to the elongated stringers of slag, which rather than detracting from toughness probably would have had the opposite effect.

Cheers
Chris

[Jeff D]

Hi Chris,

Thanks for your reply. You are correct they are taking about crucible steel not wootz. There has been a trend in using the terms interchangeably although they are different. I interpreted your question wrong. Now that I think I know what you are asking. I suspect it is the lack of hammering of the fakes that would be the problem, hammering that would not be required on crucible steel. I know you know this much better than me. Do you mind me asking, doesn't it takes multiple foldings to form the stringers, not just hammering to shape?

All the Best
Jeff

[Chris Evans]

Hi Jeff,

Originally Posted by Jeff D

Hi Chris

Do you mind me asking, doesn't it takes multiple foldings to form the stringers, not just hammering to shape?

All the Best
Jeff

Sponge iron has to be hammered extensively every which way to reduce its slag contents (by squeezing it out) - This is done as a matter of course. And the extent of hammering it receives ensures to a considerable degree its quality, though not entirely.

Without knowing the answer to your question, it is my view that some folding would have been unavoidable. But whether the ancient Viking swordsmiths went as far as others, say the Japanese, in the pursuance of refinement by way of repeated folding, I cannot say. I think that a much hammer refined blade would have represented a superior product, and this simply on the basis of labour input. Just how aware the Viking swordsmiths were of the need for extensive hammer refinement of sponge iron, I am ignorant of and here we need a knowledgeable archeological metallurgist, something that I am not.

However, I'll venture to question the presumed superiority (in the article) of a Wootz blade against one well made from sponge iron and hardened. If the ancients could quench and temper Wootz, then they indeed would have had a superior blade, but that would have required being able to heat just sufficiently to austenitize the pearlite without dissolving the carbides and then quenching, a task requiring very good temperature control, not to mention knowledge. On the other hand, steel made from sponge iron can be quenched and tempered with relative ease - This is how swords, indeed all steel implements, were made before the advent of molten steel making, and we do know that perfectly serviceable and many excellent blades were produced this way.

In a past thread we have discussed whether Wootz was quenched and tempered in the old days, and there is some evidence that some of it was. As to how they went about this and how successful it was I am not sure - Without having done any first hand experiments, or reading of any such attempts, my guess is that if high carbon Wootz is heated to the extent that a substantial amount of the carbides are dissolved, then upon quenching and tempering its microtructure would turn into a proverbial dog's breakfast with very uncertain mechanical properties.

Cheers
Chris

[Jeff D]

Hi Chris,

Thank you for your answer. Regarding the quenching of wootz, what do you make of this. Sorry this is the best picture I could make.

Thanks again
Jeff

[Gonzalo G]

Originally Posted by Chris Evans

Sponge iron has to be hammered extensively every which way to reduce its slag contents (by squeezing it out)

However, I'll venture to question the presumed superiority (in the article) of a Wootz blade against one well made from sponge iron and hardened.

In a past thread we have discussed whether Wootz was quenched and tempered in the old days, and there is some evidence that some of it was. As to how they went about this and how successful it was I am not sure - Without having done any first hand experiments, or reading of any such attempts, my guess is that if high carbon Wootz is heated to the extent that a substantial amount of the carbides are dissolved, then upon quenching and tempering its microtructure would turn into a proverbial dog's breakfast with very uncertain mechanical properties.

Cheers
Chris

Chris, I am confused by your words. I understand that old steels were made with bloomery iron, and not sponge iron. Or instead, decarburizing cast iron with high carbon content, which is more easily molten at lower temperatures. Sponge iron, as I understand it, is another kind of product. I feel much of the discussion about wootz is biased by speculations which tend to maximize, or instead, minimize, the value of this type of steel, making statements above of the facts. It is scientifically healthy to have some dose of scepticism in front of myths and distortions. But the fact is that we don´t have enough samples of wootz blades, studied and tested, and even less scientific comparisons among wootz blades and european blades from the same period. On the other side, it seems that there is another manuscript from Al Kindi dedicated to the thermal treatments of the blades made with wootz, which is not yet printed, though I understand maybe there is already an italian traslation. There are references to this work on the book Medieval Islamic Swords and Swordmaking, by Hoyland & Gilmour.

But even with the publication of the translated manuscript, I belive we will yet have many questions for years to come about this subject. I hope the archaeometallurgy helps us in the progresive clarification of many of our questions. Other discoveries look ahead on the study of the traditional swords of the world, as the viking swords seem to demonstrate. I still believe the articles about viking swords refer to a relatively clean high carbon crucible steel, and not to wootz. The swedish article mentions the presence of 0,8% refined carbon steel in one of the edges of the studied sword, and 0,4 to 0,6% carbon steel on the other edge. This opens the possibility of speculate about some specialization among the different edges of the viking swords, or at least in some of them, but it is only a good? pretext to continue our conversation. Some of the viking swords seem to be very complex in their structure, not because they are multilaminated in the japanese way, but because they have many different types of steels and irons in their composition, all welded in the make of the blade.

This kind of solution is not less sofisticated, or work intensive, than the japanese nihonto, in my opinion, but this is said with no regard of the differences on their success to have the best relation metallurgy-geometry-design, or to do with more effciency the expected job, as it is another very difficult subject to discuss with some scientific basis. Of course, this are only some of my ideas, and I can be wrong.
Regards

Gonzalo