Nimcha markings

[Philip]

Originally Posted by Jim McDougall

Ed and Philip, one of the greatest conundrums for me in understanding, from metallurgical perspective, can blades be stamped with these kinds of marks after they are finished?

Whether a blade can be stamped, engraved, or chiseled post-heat treat depends on the hardness achieved, and also the area of the blade affected by said process. The latter point is important because in various traditions, blades were differentially heat treated, the zone along the edge(s) becoming quite hard whereas the back or center remaining fairly soft. People automatically associate this technique with the Far East, but it has been observed on Western blades from a variety of sources, from hand-forged Bowie knives of the early 19th cent. to Italian rapier blades from two or three centuries earlier.

As an arms restorer whose practice involves a lot of blade polish, I have been able to observe a lot of this empirically. Since Japanese blade quenching involves only the edge zone, horimono can be carved on the relatively soft, burnished area above the shinogi and historically, many blades were decorated in this way post-manufacture. I have worked on Philippine blades with glass-hard edges, but with deep dents further back where some idiot tried to straighten a bend by whacking it with a hammer. If you can make such well-defined dents with a hammerhead, then a marking stamp can make quite an impression as well. Hit the edge with that hammer and it would likely chip or crack like the rim of a teacup.

Wootz is surprisingly variable. Many Persian and Ottoman blades with beautiful patterns are actually so soft that they can be shaped with a file, whereas a lot of Indian ones with low-contrast grainy structure are very hard. And yes, I've had to deal with some that have deep scars from percussion tools just as I mentioned above. And another thing -- a lot of Ottoman blades were subsequently decorated with aftermarket gold overlay, the steel would have to be deeply scored with a graver to crosshatch the surface, and annealing and re-tempering a wootz blade invites all sorts of problems especially if you want to preserve the watering.

The point that I'm trying to make is that you can't really generalize. These old blades exhibit a range of physical characteristics so something that may apply to some cases would not necessarily be applicable to all.

[kronckew]

Nepali Kamis (blacksmiths) routinely heat treat their blades with boiling water as a 'coolant' from a tea pot on the critical heated edge to harden that, leaving the residual heat to temper the spine a bit softer. It takes them years of practice to learn how to do it right. Better they should bend rather than snap, you can bend a soft spine one back to workable in the field, but snapped blade can't be fixed there.

[Philip]

Originally Posted by kronckew

Nepali Kamis (blacksmiths) routinely heat treat their blades with boiling water as a 'coolant' from a tea pot on the critical heated edge to harden that, leaving the residual heat to temper the spine a bit softer. It takes them years of practice to learn how to do it right..

I would imagine that the method works better on short, relatively wide single edged blades than long narrow ones. And having polished a few antique kukris in my time, the technique worked well. Edges were respectably hard, spines softer, and with a minor etch and rub-down afterward with very mild abrasive powder, a nice cloudy "temper line" can be seen.

A friend who makes knives once traveled to Thailand to see contemporary makers of daabs and other blades at work, and he reported that smiths use a rather long trough-like forge so that the edge side gets hotter, and they quench by immersing just the edge in the water bath, being careful to include the point on long curved blades, and then after some moments dunk the entire thing underwater. As you describe, it's all about technique and timing.

19th cent. Victorian writers have a low opinion of Burmese blades, but I've found, from actual polishing, that the better ones have a very precise and crisp hamon with a line of crystallization that is comparable to a lot of Japanese work. One would think that some sort of clay heat-sink, à la japonaise, was used but I've not been able to verify this. BTW, the use of these clay coatings was mentioned by the Persian scientist Mohammed bin Ahmed al-Biruni in his treatise On Iron (10th century) and highly visible differential heat treat is evident on wootz shamshir blades made in Iran through the 18th cent.

[kronckew]

The nimcha above looks remarkably like mine, with a blade in better condition.

http://www.vikingsword.com/vb/showth...ghlight=nimcha