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Granulation Chemistry?


#1

All; Can someone please explain me the chemistry behind granulation?
My apologies if this is not the appropriate place to submit the
question. Mark

Mark Silver


#2
    All; Can someone please explain me the chemistry behind
granulation? 

Eutectic bonding, the exchange of molecules to join two materials
together by the process of fusing, rather than soldering. Another
example besides granulation is keum-boo.


#3

Granulation uses a mixture of a carbon based glue and a copper salt
to stick the granules in place. Then heat is applied.

As the temperature rises the copper salt is broken down into copper
oxide and the carbon in the glue further reduces the oxide into pure
copper. This forms a molecule thin layer between the silver base and
the granule. As the temperature rises the copper molecules migrate
into the surfaces of both and an eutectic alloy forms. This melts and
binds the two together.

Am I right, or am I right?

Tony Konrath


#4
 chemistry behind granulation? 

Oppi Untracht’s “Jewelry Concepts & Technology” has it all regarding
JPM’s methods Mark.

cheers
al heywood


#5

It is not really eutectic bonding it is liquid phase diffusion
welding. The presence of a eutectic alloy is not required for
granulation. You can granulate fine gold, and gold and copper do
not form a eutectic alloy. All that is happening is a small amount
of copper is diffusing into the surface of the gold and for a brief
moment the surfaces become liquid due to the high local
concentration of copper which creates a lower melting point alloy on
the surface as compared to the bulk metal. This local melting fuses
the granules to the surface.

Keum-boo is not the same thing at all in that no melting occurs. It
is a form of solid state diffusion welding. Because there are no (or
very few) oxides present when you burnish the gold foil onto the
fine silver surface the molecules actually diffuse together into new
crystals due to the application of heat and pressure. If the
surfaces were absolutely clean and oxide free you could make them
stick together at room temperature with only pressure from the
burnisher.

Jim
James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160


@James_Binnion
Member of the Better Business Bureau


#6

Well Tony yes and no. You are right in so far as silver is
concerned that a eutectic alloy may be formed but the fact that it
is a eutectic alloy has nothing to do with the bonding. In gold
granulation there is no eutectic alloy formation. What is happening
is that the copper diffuses into the surface of the gold or silver
and creates a lower melting point alloy which melts on the surfaces
and welds the granules in place.

Jim


#7

Dear Mr. Binion, I saw the class mentioned and you were going to
teach how to bump up the metal for the mokume Gane… I am afriad I
missed it and am rather sick about it… Are you going to teach it
agah somewhere close to my area… New Jersey… HOw I would love to
be able to do it right and get interesting patterns… well lets hope
you will teach it nearer to this area… calgang@aol.com My
daughter showed up the other week with a mokume bracelet I had made
yrs ago with the Parsons class in New York with Gene Pijanowski
teaching… She wears it for the copper content for her wrist etc.
It is so beautiful … a star pattern… I had forgotten all about
it… neat… I can still see the billets we made… 20 plus layers, a
special coal fire and everyone taking their turn turing the fan
under their work… Then the pounding and pounding to get it to some
managable piece of metal,I even made a small pot about 4x4… such fun…