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Japanese Alloys


Karl Carvalho

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Guest ford hallam

Hi Patrick, Jeff,

 

nice result and collaboration there :) . I can discern grain structure in your sample Patrick, that's delicate polishing, as it ought to be done. Cheers. :)

 

Jeff,

naturally I don't know exactly what procedure you followed but the fine cracking visible on your plate may actually be the result not of impurities, but oxygen absorption. As you probably know molten copper, and fine silver for that matter, can absorb up to 100% its own volume in oxygen. The fissures I can see are the same as I've created in the past when not covering my melt with a generous layer of charcoal. Pouring into water or a closed mould ( second best option ) also helps limit oxygen absorption. Another "trick" would be to remove the outer layer of the ingot, the area most likely to have absorbed oxygen, because any potential flaws will direct the stresses deeper into the metal which can lead to a fracture. Anyway, I'm probably trying to teach you how to suck eggs as you've most likely got all this covered.

 

Regards, Ford

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Thanks Ford,

I learned from a fanatic and some of it "rubbed" off on me :)

I use a steel ingot mold and the exposed top absorbs too much oxygen. This portion is sawn off and recycled, but if I were to forge it would behave as Jeff's sample. The rest of the ingot would be perfectly fine as the Carbon layer in the mold protects the ingot. Though I still tend to lightly scalp the skin from the whole. There is still a shallow layer of oxygen absorbtion all over, but it is easily removed.

Patrick

 

Hi Patrick, Jeff,

 

nice result and collaboration there :) . I can discern grain structure in your sample Patrick, that's delicate polishing, as it ought to be done. Cheers. :)

 

Jeff,

naturally I don't know exactly what procedure you followed but the fine cracking visible on your plate may actually be the result not of impurities, but oxygen absorption. As you probably know molten copper, and fine silver for that matter, can absorb up to 100% its own volume in oxygen. The fissures I can see are the same as I've created in the past when not covering my melt with a generous layer of charcoal. Pouring into water or a closed mould ( second best option ) also helps limit oxygen absorption. Another "trick" would be to remove the outer layer of the ingot, the area most likely to have absorbed oxygen, because any potential flaws will direct the stresses deeper into the metal which can lead to a fracture. Anyway, I'm probably trying to teach you how to suck eggs as you've most likely got all this covered.

 

Regards, Ford

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What about alloys of gold

 

How pure was the gold they used for inlaying - would 24K have been "too soft" for sword fittings? I haven't used gold yet, but want to start and would like some pointers- and I want to buy a batch of gold before it doubles in price again!

 

Color palette of various shibuichi mixes

 

I think it would be really useful to have a spectrum of rokusho-patinated shibuichi, from pure silver to pure copper, in graduations of say, 5% by weight. Has anyone done that before?

 

I'm appreciating all the interesting discussion here. Show of hands- who uses the arsenic containing alloys?

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What about alloys of gold

 

How pure was the gold they used for inlaying - would 24K have been "too soft" for sword fittings? I haven't used gold yet, but want to start and would like some pointers- and I want to buy a batch of gold before it doubles in price again!

 

Color palette of various shibuichi mixes

 

I think it would be really useful to have a spectrum of rokusho-patinated shibuichi, from pure silver to pure copper, in graduations of say, 5% by weight. Has anyone done that before?

 

I'm appreciating all the interesting discussion here. Show of hands- who uses the arsenic containing alloys?

 

Brian Gold is soft, but it does work harden to some extent. Fitting made from pure gold do exist even Habaki, but they would not be pieces meant to go into battle. Judging from the colors of some of these alloys and from what Ford mentioned to me there are definitely high gold alloys. Percentages of copper and or silver added to the gold would have changed the shade of color slightly and increased durability. You will often see in sword fittings two distinct shades of gold used together for contrast. One being close to pure if not pure and the other containing a fair amount of silver which takes some of the yellow out and leaves the Gold more pale with greenish hue. At first by itself it might be mistaken for pure gold unless you already have an eye for metal color already. side by side it is obvious. Ford would be best to comment on the topic. He had serious training as a Euro Gold smith before "Turning Japanese" and knows gold better than anyone I have met.

 

I am working on the Shibuichi thing. I have 14 different percentages so far. There is a catch though. Technique in creating the alloys plays a large role in how they color. A simple gradient will not tell much about alloys outside of your test batch. How the silver is dispersed in the copper is a big variable. You can get a consistent result by letting the alloy soak a long time with the components together in the Crucible. Getting the silver to disappear to it's maximum. Unfortunately those results will not be representative of what you find in top quality fittings. Fine Shibuichi has that dispersment interrupted hopefully creating a pleasing pattern of distinct and visible silver nodules in a matrix of copper silver alloy. So you have both continuous alloy and noncontinous alloy coexisting on a macro level. Ford calls the pattern Nashigi. It can be quite attractive though I don't have a handle on achieving a quality nashigi yet. So far it is rather bla and splotchy for me. Anyhow, good nashiji will make the best quality base metal for fittings in a classical sense. In a modern sense you can get nice shades of gray with continuous alloys. There are also gold bearing Shibuichi. Progress on exploring those is limited by my budget lately.

Regards,

Patrick

I use Arsenic, but only when I have to.

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Guest ford hallam

Hi Brian,

 

not much that I would add to what Patrick has already written except to say that the gold alloy you use is very dependant on what sort of inlay you intend to do and into what ground. If you have something specific in mind I could make a suggestion. Also, are you able to make your own alloys and process the metal; ie, make sheet or wire? If not then you may be a little limited in your choices.

 

The gold alloys that we see used in antique pieces tend not to have copper added to them as this would harden the metal. The reddish bloom sometimes seen, particulary on gold habaki is the result of a depletion gilding process which includes a small amount of copper sulphate.

 

Patricks comments regarding shibuichi are also spot on. I would suggest that before you start making up vast ranges of alloys you focus on getting some sort of consistancy in terms of patination. Unless you know that your patination procedure is sound and you can recognise when it is off then all the alloy samples you may make will be hit or miss in terms of actual colour achieved. As Patrick will tell you, this is no small thing. If you can get a decent and consistant colour on copper and can manipulate the patination solution to push the colour in certain directions then you may be in a position to begin exploring the wide range of possibilities that shibuichi offers. Without that kind of grounding though you will really be flying blind.

 

I don't mean to sound discouraging, my intention is quite the opposite in fact. Shibuichi is possibly the most sensitive alloy in the Japanese pallette and achieving a good opaque, and clean colour, is often very tricky particularly if you don't really know what to expect.

 

As far as arsenic goes, I only add it to alloys in an already alloyed state. I use a commercially prepared alloy called kuromido which contains 3% As and the rest Cu. By making the required adjustments to the alloy composition I'm making I can fairly accurately add As. What I would say though, is that apart from replicating Momoyama period Shakudo and making Nigurome there is no need to use the stuff. You may have read the discussion we had here some time ago about unrefined copper. You might try your hand at processing some of the samples you can get at rock and gem shows, there is invariably a trace of As in these. Just remember to hold your breath when smelting :rolleyes:

 

regards, Ford

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Hi Brian,

 

before you try yourself on gold alloys try to work for a while in silver. It will help to understand the working properties of precious metals without being too expensive. If you master sterling silver you will find it easy to work with gold. (Exept some red and white alloys and low karat alloys - these metals are a bit tricky)

You will find lists with coloured gold alloys in every technical book on jewelry.

 

regards,

Karl

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Guest ford hallam

Hi Karl,

 

you are absolutely right, Brian would do well to gain some experience in inlay using silver rather than gold. I'd suggest fine silver though as it is softer and doesn't discolour as badly as Stirling silver when you come to patination. Unless of course you want the inlay to look like a very pale shibuichi :rolleyes: The working properties of Japanese gold alloys ( in classical work ) are also much closer to fine silver. One can also experiment with copper wire if inlaying into steel, electrical flex is a handy source for very fine copper wire.

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Thanks for the replies,

 

I am interested in using gold for mostly inlays (takabori zogan, hira-zogan and sen-zogan), but also a little for overlays (nunome-zogan). I've some experience inlaying pure silver and forming it (my cricket menuki), so I think I am ready for gold. I'll just go carefully and of course keep all the chips. I have a few specific project in mind that would work best with gold.

 

I don't have easy access to foundry equipment, but I know a guy at MIT who now runs the foundry, and I can work with him if and when he's free to be there. I read about the inhomogenous shibuichi mixes. I'd like to try that sometime, but for now I think I will be happy enough to order some shakudo and shibuichi from Shining Wave, just to get familiar with the basic alloys before I try some variations.

 

I do have a large lump of homemade shibuichi, 1/4 silver in copper. I think while I was melting it it may have absorbed oxygen, because as I was hammering it, it kept cracking on the edges. Should I just melt it down and surround it with charcoal, and then re-cast it into water?

post-1626-1190087694.jpg

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I suspect I have been rather lucky creating the alloys. I have a small billet of 4% shakudo I made nearly 30 years ago that I have used portions of without any problems. At the time I used a simple ingot mold. I have also made the 3/4 shibuichi without difficulties. The forgings with this alloy were not bad. It is not nearly as maleable as copper and will crack if I overstress without annealing. Not sure what I am doing right and I do not feel we should be too intimidated by the process. I recall an indepth paper by members of the Society of North American Goldsmiths on the making of several different shibuichi alloys. Brian, The image of the mounted tsuba with the mayfly, is that your work?

 

Fred

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