Hunting sword - weird color

[Drabant1701]

I recently bought a indian hunting sword. I know it not actually made for hunting, and is more of a novelty item, although it is sharpened. But I liked it, so I bought it. I noticed that the upper half was lighter, and the side toward the edge was darker, both left and right side are the same way.

I wanted to lightly etch the sword with lemon since I saw watered steel. So I cleaned it with oil and 0000 steel wool. Then degreased with soap and after that alcohol. After that I etched it with a lemon for 10min, dryed and oiled it. I was pleased with the etch but the sword i still darker on the bottom half. It is hard to show in a photo and is more obvious in real life.

The question is: have anyone seen this on other swords? What could be the cause of this difference in color?

My thought was that someone has sand papered the upper half, and that is why it is lighter and wont etch as much. Or thay the edge has been hardened with heat and therefor is darker. One thing that is a little odd is that there is a streak of dark in the light section and its on both the left and right side, in the same place. Now this had me thinking that it may actually be the steel itself that is darker on the edge side, on purpuse or not. Im rambling a bit it may well just be dirty, I cleaned it well but I wont use anything more than 0000 steel wool and wont etch again so it is all just speculation.

Any opinions are welcome.

[Tim Simmons]

This is not my field of interest though I have seen similar decorative swords with a tempered and sharp blade. Perhaps our Asian experts might give more information.

[Battara]

If the top part was polished bright and then you give it a light etch, it would indeed not darken as much as the bottom part.

The idea that there is differential heat treatment is possible, but I think less likely.

Great piece in any case!

[Oliver Pinchot]

Jose is right. It's the way the blade is heat-treated.
It's a desirable characteristic, congratulations.

[kronckew]

yes, the different crystallisation patterns from the softer spine down to the harder edge show as different colouring. the indians were quite good at differential heat treatment. and still are. nepali kami that forge khukuris heat their blades to the right red colour (by experience) then quench just the working part of the edge with a tea kettle full of boiling water. the residual heat in the spine tempers the edge and thats that. using clay along the spine area does much the same, and is a bit easier to accomplish with larger blades and less experience.

[Drabant1701]

Thank you everyone for your replies. I cataloge all new aditions to my collection and like to have as much information about the items as possible, your help is much appriciated.

Originally Posted by kronckew

yes, the different crystallisation patterns from the softer spine down to the harder edge show as different colouring. the indians were quite good at differential heat treatment. and still are. nepali kami that forge khukuris heat their blades to the right red colour (by experience) then quench just the working part of the edge with a tea kettle full of boiling water. the residual heat in the spine tempers the edge and thats that. using clay along the spine area does much the same, and is a bit easier to accomplish with larger blades and less experience.

That is very interesting. Thank you.

[kronckew]

just to show the extremes of colourisation due to steel compositions, here is a recent knife. the back is of twisted 'damascus' (pattern welded) and the hard steel cutting edge joins serrated to the middle rod of mild steel. the actual cutting edge is bright because it's been sharpened on a diamond 'stone'.

[Philip]

Originally Posted by Battara

If the top part was polished bright and then you give it a light etch, it would indeed not darken as much as the bottom part.

The idea that there is differential heat treatment is possible, but I think less likely.

Great piece in any case!

Jose, it seems to me from experience that if you polish the upper side bright and etched the whole thing, the lower side will darken if the composition (crystalline structure) of the steel gives it that tendency, regardless of what you do to the surface. Wootz reacts to etchants according to its own nature.

Differential heat treating was not only possible, but it was indeed widely practiced by smiths working in "pulad jawhar" (wootz) in Iran and India. I have polished many blades which show this effect. The delineation in many cases is quite crisp, and with a skilful polish and etch, on an exceptional blade you can see a narrow, cloudy crystalline border between the zones. This is akin to an identical effect called the habuchi which is quite distinct on some Japanese blades and is a much-desired aesthetic effect. The fact that its appearance is not limited by culture or geography is also borne out by its emergence when I have polished some outstanding Burmese dha and knife blades as well. Some of those are truly dramatic.

Differential heat treating of edges may be done with or without the use of a layer of refractory clay to cover the body of the blade and provide a sort of heat-sink (this controls the amount of heat absorbed in each area, and therefore the hardness after the blade is quenched) . Moro barong blades, for example, were treated without the layer; the result is not artistic but is the functional result leaves nothing to be desired. In such cases, the blade is merely held edge-down and moved rapidly to and fro in the forge to bring the edge only up to heat, followed by dunking in water or oil.

Most people think that the use of a refractory clay layer is a specifically Japanese technique. Wrong! Read this from the treatise, "On Iron", by Mohammed ibn Ahmed al-Biruni (10th cent. AD):

"During quenching, they [the smiths of Iran and India] coat the broadside [full width] of the sword with suitable clay, cow dung, and salt in the form of a paste, and test [i.e. mark out] the place of quenching at two fingers from the two sides of the cutting edges. Then they heat it by blowing [the hearth with bellows], the paste boils, and they quench it and cleanse its surface from the coating..." (trans. Brian Gilmour and Robt Hoyland in MEDIEVAL ISLAMIC SWORDS AND SWORDMAKING, Oxford 2006, p 152.

In my more limited experience in working with the steel blades of late medieval and renaissance-era European swords I detect signs of a similar albeit less-developed concept at play. I'd love to investigate this further on damaged blades as they become available, since the aesthetic standards of collectors in these fields tends to frown on polishing and etching blades.

[Miguel]

Originally Posted by Drabant1701

Thank you everyone for your replies. I cataloge all new aditions to my collection and like to have as much information about the items as possible, your help is much appriciated.



That is very interesting. Thank you.

Anthony Tirri in hi book Islamic Weapons Maghreb to Moghul names this type of sword with hunting scenes as Shikari.
Thank you for sharing.
Miguel