Gravity test

Questions on polishing, restoration, conservation + manufacturing techniques

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amena
contributor
Posts: 663
Joined: Fri Jan 20, 2012 8:42 am

Re: Gravity test

Postby amena » Wed Sep 20, 2017 1:07 pm

EUREKA.
I finally found the puzzle solution
At pag. 9 of the book "Manuale dell'argento" di Giovanni Buzzi ( https://books.google.it/books?id=1SKVAw ... &q&f=false)
Image
As for investment ingots, normally made in pure silver , it's easy to roughly check the authenticity: just compute the volume (width X thickness X height) in cubic centimeters and multiply by the specific weight that in this case is equal to 10,49. This rule does not apply in the case of ingots produced by 'Metalli Preziosi", a former market leader. The M.P. coined the investment ingots starting from a powder obtained in chemical way, not from laminated sheet. The powder was pressed and then sintered, a heating process near the melting point. The coined ingot in this way has a much lower density and to meet the weight it is necessary to increase the volume, usually the thickness. It's all perfectly legal , but you can not use the method described above and the potential buyer might be misled by being in front of an ingot with an increased volume.
You can not distinguish, just by looking, the difference between a coined ingot and this sintered one, but finally everything is explained.

Joerg
contributor
Posts: 353
Joined: Tue Aug 02, 2005 6:41 am
Location: Switzerland

Re: Gravity test

Postby Joerg » Wed Sep 20, 2017 2:26 pm

Congratulation!
We all had to wait long, but what this text states makes sense. Sintered...
Was lange währt wird endlich gut.
All the best
Jörg


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