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Tamahagane Analysis + Question


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A scientist that I know is analyzing samples of tamahagane that I picked up during my recent trip to Japan (from the NBTHK in Tokyo).  To his (and my) confusion and surprise, he found ~20% copper (Cu) alloyed with the iron!

Since he didn't find any copper minerals in the iron sand (satetsu) sample, the only guess we have is that somehow some copper-bearing mineral was accidentally or purposefully mixed in the tatara during the smelting.

Could anyone please comment on this and shed some light?  Thank you!

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Hi J.

I also purchased some when I was over there, when I was home I showed it to all my fellow collectors, which had some but bout 30 years older.

 

the visual difference was huge, so after discussing the two, we had agreed that they are sell the lesser scrappy parts as they were probably to poor to make swords from.

 

this may be why the copper is so high. just my thoughts,

 

regards H

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Yeah, I agree with Hamish that you probably got some of the unusable stuff, John. But after visiting the Bizen Osafune forge on my last trip, I really can't figure out where the copper would come from. Maybe trace amounts would show up, but I'm not sure that you could even get 20% copper to alloy with iron. Could his analysis equipment be miscalibrated or defective?

 

Ken

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Thank you all.  Yes, it is quite bizarre.  I have asked him to sample other parts(?) of my ores.  There is also another, much larger ore that was sent directly from a smith's forge in Seki, and he will be analyzing that sample as well.  I'll update with any interesting information.

By the way, any suggestions about where on an antique nihonto would be most useful to take a sample for metallurgical analysis, without diminishing the value/risking its overall integrity?  Wouldn't there be a lot of variation depending on the portion of the blade?  My scientist friend only needs to take about 1 cubic millimeter, but my guess is that a sample from the nakago (I was thinking from around the mekugi-ana, to be on the safe side) would yield different results than from say, around the ha-machi.  If the construction involves complex lamination, then there would be even more variables.

In case anyone is wondering, the samples will be taken by another researcher from the archaeology/anthropology dept of the university, with very sensitive/fine tools... (just in case anyone was horrified, imagining someone going after a nihonto with a chisel and hammer~  lol ).

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By the way, any suggestions about where on an antique nihonto would be most useful to take a sample for metallurgical analysis, without diminishing the value/risking its overall integrity?  Wouldn't there be a lot of variation depending on the portion of the blade?  My scientist friend only needs to take about 1 cubic millimeter, but my guess is that a sample from the nakago (I was thinking from around the mekugi-ana, to be on the safe side) would yield different results than from say, around the ha-machi.  If the construction involves complex lamination, then there would be even more variables.

 

Hi,

What if you removed the habaki and see if it is scratching any part of the piece and take a small scrape from there after cleaning? It is already scratched. Just be sure that no trace of habaki material is left there.

 

Also, dont do this before consulting with someone far more knowledgeable than me, just an idea...

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where on an antique nihonto would be most useful to take a sample for metallurgical analysis, without diminishing the value/risking its overall integrity?  From the side of the mekugi-ana on the nakago would do the least damage but still would do damage.  Anywhere else on the blade, even if only a cubic mm, would be desecration.  If you can find a broken blade have at it, but since this analysis has been done before and you would be adding nothing new, leave intact blades alone please.

Grey

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No, no, no! There are a number of hand-held instruments on the market that you can simply use by pointing them at the blade, & reading the various percentages of elements. These instruments start at around $30K, so you'd probably end up using a service, rather than buying one yourself. I've used a Bruker handheld XRF spectrometer for several of my engineering projects (https://www.bruker.com/products/x-ray-diffraction-and-elemental-analysis/handheld-xrf.html), but just rent it for a few days or weeks. X-ray diffraction won't harm a single atom of your kouho blade!

 

Ken

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