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Restore Or Not ?


peterd

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Based on how much I love that bamboo...I would say yes...definitely.
Ford should be able to recommend someone, I don't think his schedule is allowing him much new work currently. But there are others that are well capable, and this would look great. If not..sell it to me, and I will have it done :)

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Hi guys, Ford said he would take care of it. This tsuba is even brighter than in the first picture. I think it would take 20 years to tone to something really nice and i will probably be dead by then. Will show pictures when i get it back.

Thanks for all comments, i like opinions  from both sides of the fence.

Many thanks 

Peterd

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I just want to make a few comments regarding brass tsuba.

 

Firstly it's important to note that shinchu (the Japanese term for brass) and sentoku are not the same thing. Shinchu can be forged and is malleable whereas sentoku is not workable in that way.

Sentoku is a casting alloy and will break if any forging or hammering is attempted on it.

 

Shinchu is an alloy of copper and zinc, with zinc typically being in the 12 to 35% range. Traces of lead are inevitably present, generally less than 1%.

 

Sentoku is a more complex alloy that is typically Copper with zinc 10 to 15%, tin 5 to 8% and lead 6 to 8%. Other traces elements are present also.

 

And although two generations of Mitsuhiros made tsuba featuring 100 monkeys, horses and the like which bear inscriptions describing the metal as sentokukin/gane this alloy is in fact quite different. These are actually shinchu with a little arsenic in the mix.

 

Sentoku as we understand it today only entered the Japanese metalworking tradition in the Meiji period. It wasn't used for tosugu previously.

 

Now to the patina.

 

The essential componant of patina on traditionally patinated non-ferrous tosogu is cuprite. This is a red copper oxide. It follows then that copper patinates naturally to various shades of red, the red cuprite colour being modified by traces of other oxides in the patina as a result of other elements in the alloy or by means of cunning alterations to the basic patination mixture, temperature and speed/time of the patination process. Brass patina owe their yellowish/ochre  tint to the presence of white zinc oxide in the patina layer.

 

Because zinc is more reactive than copper we frequently find that the surface of previously patinated antique brass pieces are zinc depleted. This means that when a new patina develops it will be quite different to what it was originally and often much darker and copper-like.  The point being that while copper alloys like brass may indeed develop a decent patina over time the new colour will almost certainly be different from what the maker planned. The recovery of original and authentic patina is not always possible but there are processes that can be used that compensate for the zinc losses.

 

This is a close up of an early Edo period tsuba (Higo) showing the results of surface de-zincification. The structure that is revealed is called dendritic and is essentially copper rich (with a little zinc trapped in it). The missing part was zinc rich. Zinc has a much lower melting point than copper so as the alloy cools the zinc rich parts are squeezed in to the gaps of the cooling copper network/dendrites. In this example the result of the zinc loss is very clear in areas that are protected from fingers but on more exposed areas that metal has been 'polished' smooth again by years of handling.

post-164-0-59828200-1486902832_thumb.jpg

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