Gilt Tsuba

[JohnTo]

I bought this tsuba a couple of months ago as part of a mixed lot and was going to post it on the notice board when I had done a bit more research.  One of the features of this tsuba that I was going to write about was the base metal, as determined by Archimedes principle. I notice that the topic of metal composition by this method has cropped up recently (Nick Ricupero), so I thought that I would post what I have.

The tsuba is essentially round (7.3 cm high, 7.0 cm wide, 0.35cm thick) and has a thin gold gilding over an unknown soft metal base.  Each side of the tsuba is carved on low relief and depicts a tranquil scene of one or two thatched huts next to a stream, one scene also having a footbridge.  The trees also appear to have some shakudo in their makeup, but may be due to gilding rubbing off.  At first glance the surface appears to be nanako, but closer examination reveals the texture to be more random in shape and distribution than nanako.

I have only found two examples of gilt tsuba so far.  The first is illustrated in Masterpieces from the Randolph B. Caldwell Collection, #16 (a late Muromachi piece, carved in low relief with a nanako ground.  The copper base metal clearly visible around the nakago).  The second was sold at Bonhams, 7 November 2013, lot 197 and signed Hishu Ngagasaki no ju Raitensai.  This was carved in low relief and the photo looks like the plate was textued in a similar way to mine, rather than nanako.  The gilding was worn and a brown metal underneath was showing through.  I must have actually seen and handled this tsuba, but, having no interest at the time, have no recollection (old age probably).  This 18thC Hizen tsuba was most like mine and so I will put mine from the same school (based on a limited sample population of two!).  How popular were gilt tsuba and who wore them, as they look a bit gaudy to me?  Any other ideas?

Now to the main theme of this posting.  What is the base metal of this tsuba?  The inside of the nagako ana looks like brass in both colour and in the cut of the file marks.  However, the rim shows a brown metal where the gilt is worn and looks like bronze or shibuichi.  Like other Nihonto correspondents, I also remembered Archimedes, who thanks to his personal hygiene routine was able to exclaim ‘Eureka’ and demonstrate that the king’s gold crown had been debased with silver.  I did the experiment as follows, using my wife’s kitchen scales.  Suspending the tsuba with a piece of fishing line (see photos) I was able to determine its weight (148g).  Bringing up a jug of water to submerge the tsuba reduced its weight to 130g.  Thus the average density of the metal in the tsuba was 148/(148-130) = 8.2 (OK, let’s say 8.0-8.5 as weights were only determined to nearest 1g).

Looking up density tables for metals I found that the density of steel is 7.8, brass is 8.4-8.7, bronze is 7.4 -8.9, depending upon tin content, copper is 8.9, silver is 10.5 and gold 19.3.  So it looks like the base metal is either bronze, or a more likely Japanese brass alloy with increased density.  I did not expect it to be solid gold.

Regards, John

(Just a guy making observations, asking questions and trying to learn) 

[John A Stuart]

I enjoy the curiosity. The sad fact remains with all the composite ranges available all you can posit is that it is not pure silver or gold. John

[JohnTo]

Hi John,

I did not mean to imply that I had definitively identified the alloy by its density.  I have shown that its not iron or aluminium (modern forgery) on the low density side and not silver, gold, or lead in the high density end.  The Japanese kinko used lots of alloys when making tsuba.  Ford gave a talk at the Asmolean Museum in 2016 on Japanese brass and showed the collection of Japanese alloys from the Victoria and Albert museum and I seem to remember that they have about 20 ingots of alloys, collected as definitive types in the 19thC.  Ford is doing research on these and comparing the original wet assay results with modern spectroscopic ones.  Maybe he will do some density measurements.  I expect that many of them will be in the range of my tsuba.

Out of general interest I read that tungsten has been used to make the core of fake gold ingots as it has almost the same density as gold.  Luckily the forgers of the crown that Archimedes investigated was silver, or he would have paseed it as genuine.

 

Regards, John

[John A Stuart]

Yes, more effective indicating what it isn't. Still an interesting experiment. Here is a screen-shot pointer to an article where colour of bronze may indicate content. John

[Baka Gaijin]

This may be of interest:

 

https://www.mastermeltgroup.com/wp-content/themes/mastermelt/files/documents/pm/ScrapBuyersGuide/?page=8