What are the benefits of folded steel?

I assume when you say "folded steel", you are talking about Damascus. In today's world, a more accurate term would be pattern welded. The origonal Damascus Steel was produced from an ingot of smelted iron. As smelted, it contained many impurities, and a very high amount of carbon. Through heating, hammering, and folding, the impurities were worked out of the material, as well as carbon being "burned" out. This was a necessary operation to produce a suitable material for a knife/sword blade. At the time the advantages were a blade of superior quality, compared to other materials used for knives/swords. The closest material available today is know as Wootz steel. Jumping forward to modern times. The main appeal for most, of pattern welded steels, is their beauty. There is much controversy about the subject, but I personally believe that through the proper forging of a blade, there are many benifits to be had. And as for the "folded" blade, I enjoy them for their endless patterns and possibilities.

Ed Caffrey
"The Montana Bladesmith"

Folded steel is different from pattern-welded steel. The term refers to a tradition which I only know to have existed in Japan.

A smith would take the single piece of steel he planned to use to make the sword or knife from, and hammer it out flat and wide. Then, while it was still hot and soft, he would fold it over itself, which made it thicker, not as spread out, and distinctly two-layered.

Then he'd grab the hammer again, flatten it out again, and fold it again, and get a four-layered piece of steel. The next step gives him an 8-layered piece, then 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, and 32768, if he goes up to 15 folds, which is the record.

Each time the steel is tortured like this again, it gets a bit more pure because nasty stuff other than steel comes out in the process. So does some iron and carbon, the essence of steel, so the billet also loses some mass each time through the cycle, but that's OK if you compensate by starting with more steel than you intend to have in the final product.

The process serves a few purposes. It removes impurities, which amount to disruptions of atomic structure, which would mean weakness if they were left there. It also tends to distribute whatever atoms are in there (especially carbon) fairly more evenly through out the piece, "homogenizing" it. A piece of steel that's not the same formula throughout will also have structural problems that make it weak. And, finally, the layering, once you get well into the thousands, tends to promote the formation of crystalline structure in the atoms' arrangement, which is also good for strength.

You increase the benefits significantly up to around 10 folds. After that, it doesn't makes things worse or better, you're just working a lot and making the billet a little bit smaller and lighter. This dwindling-mass factor could be used to advantage; it was common for a smith to use the last few folds just to control the size of a billet in which the metallurgical standards were already met.

It was a way of dealing with impure iron ore (acutally an iron-rich volcanic sand, I think) called "tamahagane" with the best technology and technique that was available. A modern steelmill can produce huge amounts of steel, in various shapes and sizes, in almost any precisely-measured formula, which outdoes folded tamahagane in every way that folding was meant to improve, at a cost that's microscopic by comparison. But the ancient Japanese smiths didn't have modern steelmills or even our understanding of the chemistry and atomic physics at work, so they came up with the neatest trick they could. One guy I know on swordforum.com, who often has to talk some reality into people who think there's something magical and perfect about old Japanese swords, refers to their steel as "modern 1060 with crud between the layers".

Folding is still done by some smiths, for a couple of reasons. One is a matter of tradition, which tends to be a much more driving force in Japanese culture than in ours and lends an air of history to even a modern-made blade. Another reason is art; the blade of a Japanese sword or knife shows off some interesting subtleties within the metal which I can't quite describe, and a lot of this depends on the impurites and their not-quite-even distribution, which folding leaves and a modern piece of 10xy series steel doesn't have. Smiths at swordforum.com periodically discuss the challenges of getting a Japanese-style sword to look the way they want it to using modern steels such as 1075, W1, L6, etc.; modern, scientifically conditioned stuff can sometimes be just a bit too perfect to have quite the personality that an artistic smith wants.

I'd go back to my above post and edit it if I could, but I either never figured out how or else forgot.

I left something out. Ed's post above mine mentions the way a knife can look when it's been pattern-welded, and I also mentioned appearance as a significant outcome of folding. But we're talking about two different processes with different kinds of outcomes.

The appearance of a pattern-welded blade can often be the kind that jumps out and screams at you, the stark contrast between colors or shades of the metals in question being quite striking. These knives often remind me of the kind of wood that's used in highly decorative functions, with its strongly visible grain pattern and long, sweeping lines (usually).

The styles of appearance offered by folding and the differential quenching and multi-stage polishing that tend to go along with it (as a parts of the same blademaking tradition) are more subtle, appearance tends to shift with the light. A camera can practically never really catch what's going on. This is the kind of stuff you want to look at very closely. Most of the words to describe this stuff in any detail are Japanese, but when using English to compare and contrast two blades' appearances, they tend to resort to words like "texture", "blending", and "smoothness" or "roughness", as if they're trying to describe the differences between silk, linen, and a soft cotton blend.
Very succinct explanation guys. I might add that, at no time was the steel used to manufacture Japanese weapons ever in a truly molten state, as it is with modern homogenous steels. The Japanese smiths ability to produce a laminated steel of comparative "purity" (for the time period) was certainly a factor in the legendary strength of the katana, but the differential hardening (the yakiba or hamon) was just as (or more) important. I agree that homogenous modern tool steel is far in advance of the simple layered carbon steel of old, but just as with modern blades, the heat treat is a real deciding factor, especially with a sword. Those ancient smiths really knew a trick or two.

Regarding the multi-step polishing used on Japanese swords, a lot of people are amazed to learn that a good polish can cost around $150 per inch. That times, say, 28" comes to over $4000 just for a top polish. If you get the opportunity to view a really good sword in full Japanese polish, you'll see that it's worth it. An apprentice had to study for at least ten years before he could attempt to polish a good blade. His training included detailed sword appraisal, otherwise he might not know which subtle details a particular smith or school imparted to the hamon or shape of the blade. A poor polish could ruin a very fine sword.

[This message has been edited by Rick (edited 16 August 1999).]
I've watched two different sword makers using
traditional Japanese methods learned in Japan
and the base started with ore being smelted
so that at one point is was in a molten state. The small amout had broken schards of
metal from previous forgings added to the
melted ore then the folding process began. I don't remember the number of layers in the
end for either maker, but it was substantial.
The end product was homogenous and with any
layering process with many layers the end
product migrates to the point of being blended to a fineness that is difficult to
observe without magnification.


Don't walk in tradition just because it feels good!!!!!
Romans 10:9,10
Psalm 91

Hi Goshawk, my understanding about the ore in a tatara smelter is that, at around a maximum temperature of 1200-1500 degrees C, the impurities in the metal, which melt at a lower temperature then the iron itself,
liquefy and run off as slag, leaving the relatively pure iron behind. The point is that the tamahagane doesn't have an even distribution of carbon. If you look at a cross-section of the iron, it's full of gaps and patches of varying carbon content. It's this lack of uniformity that adds toughness and produces some of the interesting visual effects in the final product.
Unless I missed it reading the posts, one of the major advantages of damascus is to combine different steels providing one hard steel to provide for good edge retentio and one soft steel to provide toughness.

Other than being prone to rust and corrosion, some old Parker damascus bladed pocket knives from the 70's I own and use outperform any stainless steel I've used.

I've recently acquired a few "damasteel" bladed knives which appears to be a stainless damascus. Haven't used or sharpened any of them. How do they perform?

Knife Outlet

Sorry for the topic drift. I've always heard that most modern damascus is primarily about looks first, performance last, but I've had good luck with a blade made from Devin Thomas stainless raindrop damascus. I haven't used it hard, but it seems to hold up about as well as 440C. "Damasteel" makes stainless powder metal damascus. I'm not sure if this is "true" damascus or not. Here's a link to their site:
Yes Fred,

I would like to know that too.

Is modern day damascus useable or just pretty?

BTW guys, thanks for the good thread.
Damascus/pattern-welded steel can be perfectly usable or you can make a crappy excuse for a knife with it, just like with any single type of steel. For functionality alone, it wouldn't be worth the bother, because it isn't any more superior than inferior. So the extra work involved is justified only for people who think that stuff looks good. (I think it's ugly.)
We've cut the rigging and it is adrift.
Damascus or pattern welded or folded can
be made to function extremly well if the right steels and procedures are used to produce the final product, however most isnot. Most is made in the name of art. As
we have become more... what is the word..
more civilized..we turn to things that are
convienent, fashionable, expedient and feel
good to take care of our appetites and more
and more want the government to take care of
us and now depend on it while they take more
away. ok I'm off the IVORY or is it the DAWN box.

Don't walk in tradition just because it feels good!!!!!
Romans 10:9,10
Psalm 91