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Posted

It's only very slightly magnetic, and I'm not sure..

 

Don't want to buy an acid test kit, but I want to be sure before I do anything with it.

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Posted

Silver has a very weak paramagnetism. So not sticking to a magnet much is good. Ice test; silver will melt ice quickly. Far faster than iron. John

I have a ton of silver coins/bars and the ice test is way cool. Also just dropping it (not from chest height!) on a hard surface will give a sound unlike other metals. There are even apps now for this, unreal world.

 

Could also be shibuichi (copper/silver alloy).

  • Like 2
Posted

Copper can also exhibit paramagnetism so as far as the whole gamut of Japanese non ferrous alloys goes the magnet test is not helpful I'm afraid.

 

As for the ice trick...

 

The thermal conductivity of silver is slightly higher than copper, yes. Silver is 407 W/mK and copper is 386 W/mK. But unless you're comparing two pieces of metal of exactly the same mass (that being the heat sink) and can ensure exactly the same surface contact between the ice and metal (not to mention the same size of ice) this really can't be taken as any sort of reliable test either.

 

For what it's worth the tsuba under discussion has a suface texture that makes me a bit suspicious. I would guess that it might be a cast brass copy with a layer of tarnished (deliberately) silver plating.

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Posted

Give the tsuba to a grade 9 science student and ask the student to determine the density of the tsuba. Then check the charts to determine which metal it is.  silver 10.49 g/cm3

  • Like 4
Posted

Give the tsuba to a grade 9 science student and ask the student to determine the density of the tsuba. Then check the charts to determine which metal it is.  silver 10.49 g/cm3

I was wondering why no one went this route. It was the first thing that came to mind.

Posted

The whole density approach is unreliable is because pre-modern metals are never 100 percent one single metal. If this was a reasonablle analitical approach proper scientists would be using it in the real world.

 

For an introduction to modern scientific investigation and analysis of ancient artefacts I would recommend; ' https://www.amazon.co.uk/Science-Past-Sheridan-Bowman/dp/0714120715/ref=sr_1_4?ie=UTF8&qid=1496353379&sr=8-4&keywords=science+and+the+past"

 

In fact it's entirely feasable to devise an alloy with the same density as solid silver but with no silver being present at all.  A number of bronze alloys might be easy candidates.

Posted

So we know how not to check it.
So Ford...how would someone conclusively check if they wanted to, or is this beyond the average means of the collector out there?

Posted

Hi Brian

 

XRF analysis is probably the most reasonable way to find out what it is. Having said that a good understanding of what sorts of elements are likely to be in Japanese alloys (and why and how they are there) is important to properly understand the numbers.

 

An alloy of copper with only 20% silver can be treated to look like pure silver by leaching the copper from the surface. This is called depletion silvering and was very common in Edo Japan. Similarly a low carat gold alloy can be made to look like pure gold be leaching out the silver and copper from the surface, that'd be depletion gilding and was also common wherever gold was used. So the use of terms like solid gold and solid silver may be a bit deceptive.

 

As an example (and this tsuba, if it is silver plated, would pose a similar problem) some analitical work carried out by an Italian team at the Museo Stibbert recently included a copper iroe tsuba. The results on an inlaid fish were interpreted as being shakudo as it apeared to be made of copper and traces of gold. What had been ignored was a trace of murcury also. So in fact what it was was a copper fish with a rubbed fire gilt (kin-keshi) effect on the scales. To be fair the tsuba was a bit tarnished and the colour of the inlays unclear but never the less it shows how by just having raw data it is still possible to get an innacurate result.

 

There are many other issues that need to be taken into account when interpreting analysis results. If this tsuba is silver and supposed to be Edo period then it had better also contain about 0.3% gold. If not I would suspect a modern refined silver. If it's brass there are similar tell tale trace elements that will reveal it's age too.

 

Touchstone and acid tests won't help with anything beyond the common precious metal alloys. Plating complicates things.

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