January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Mar 28, 2024 6:05 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 9 posts ] 
Author Message
 Post subject: Casting Platinum
PostPosted: Fri Jan 31, 2014 9:12 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
We're having an ongoing discussion at work, about when platinum started to be cast for use in jewelry.
Any thoughts?


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Fri Jan 31, 2014 9:54 pm 
Offline
Valued Contributor
User avatar

Joined: Sun Jul 22, 2007 5:58 pm
Posts: 294
Location: California desert
As a numismatist also, I do know that Russia first produced 'circulating coins' ( 3R) in 1828 in platinum, also several medals ( some quite complex and large), but stop in the 1840s. My thoughts would be that jewelry would be about the same time or shortly after, as it was valued about 1/2 the cost of gold and minters and jewelers have always had many common needs and techniques. I think Siberia had quite a bit of platinum rather close to the surface at the time.


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Sat Feb 01, 2014 1:12 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Not really, platinum was not able to me melted for use in jewelry before 1901. It melts at 3,215°F (1,768°C)
Until acetylene and hydrogen torches were developed, platinum was not used in jewelry, except as an inlay,


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Sat Feb 01, 2014 2:57 am 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
Precolumbian native Americans made platinum jewelry iirc, though I don't remember all the details. Egpytians unknowingly incorporated small numbers of platinum nuggets along with gold nuggets in some pieces though that hardly counts.

_________________
Rough and cut classic and exotic synthetic gems:https://store.turtleshoard.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Sat Feb 01, 2014 7:07 am 
Offline
Gemology Online Veteran
User avatar

Joined: Wed Dec 16, 2009 5:03 am
Posts: 921
Location: Paris
Hi ,

Some references in french and bibliography in english

cf : A propos de l'utilisation du platine à Esmeraldas, Equateur

http://www.persee.fr/web/revues/home/pr ... 180_0000_2

We can read that there was an ore ductile platinum in the alluvial deposits in Choco ...



Quote:
Dans une analyse critique du travail de M. Bergsee sur la métallurgie et la technologie de l'or et du platine chez les Indiens précolombiens d'Esmeraldas1, M. Donald Morton, de l'University Museum de Philadelphie (Pennsylvanie), donne de très intéressants commentaires du Dr E. -M. Wise 2, directeur adjoint du Laboratoire de recherches de la Compagnie internationale du Nickel de Rayonne, au sujet de la possibilité de l'emploi par les anciens orfèvres d'Esmeraldas d'un minerai de platine ductile dont la présence a été signalée dans les alluvions de la côte du Chocó. Voici les quelques phrases très suggestives du Dr Wise citées par M. Horton : « ... J'ai discuté de ces questions avec des amis qui connaissaient bien le platine déversé continuellement par les dépôts alluvionnaires du Chocó... on remarque que ce platine existe sous deux formes assez distinctes, l'une angulaire brillante qui ne semble pas être ductile, et l'autre irrégulière présentant des déformations considérables lorsque les morceaux ont été roulés dans les graviers du lit de la rivière et qui serait ductile. Les deux types contiennent environ 85 °/0 de platine. « II est probable que des échantillons de la variété ductile, d'une taille suffisante, ont pu être façonnés рaг martelage sans aucun traitement spécial. Il semble raisonnable de supposer que les Indiens ont utilisé des masses de platine ductile chaque fois que cela était possible et qu'ils ont eu recours à l'assemblage de petits grains ductiles seulement lorsque des masses plus grandes de matières premières ne se trouvaient pas à leur disposition... ». Si des grains de platine non travaillés, rencontrés en compagnie des bijoux d'Esmeraldas, s'avéraient être de cette même qualité ductile, il serait évidemment plus aisé d'expliquer comment les Indiens ont réussi à utiliser de façon si extraordinaire ce métal apparemment infusible avec les moyens dont ils disposaient. En premier lieu, il serait intéressant de savoir à quel facteur ce platine doit sa ductilité, en général, dans la nature, le platine n'est pas pur mais il contient de l'osmium, de l'iridium, du palladium et aussi, parfois, du cuivre et du fer. Dans le platine de l'Oural, ces deux derniers métaux peuvent atteindre une proportion de 5,31 °/0 pour le cuivre et de 14,77 °/0. pour le fer. Il serait peut-être possible que le platine de Chocó et de la côte de l'Equateur contienne, à l'état naturel, de l'or en quantité suffisante pour jouer le rôle que lui attribue M. Bergs0e dans la fusion du métal. Dans ce cas, les Indiens n'auraient pas eu à intervenir artificiellement par l'adjonction d'or, mais auraient pu directement façonner les morceaux de platine et d''or par chauffage et martelage, ainsi que l'а exposé M. Bergs0e.
H. Reighlen.

- 1. Bekgs0e (Paul). The metallurgy and technology of gold and platinum among the pre-columhian Indians. Ingeniorvidenskabelige Skrifter, Nr. . A 44. Copenhague, 1937. Une analyse de ce travail a été donnée dans le Journal de la Société des Americanistes, Paris, t. XXXII, 1940, p. 293-295.
- 2. American antiquity. Milwaukee, t. IV, n° 1, 1939, p. 87.


_________________
danielle

"I always believed in being myself"- Thelonious Monk


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Sat Feb 01, 2014 11:31 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Remember the question is not when did we first see platinum in the archaeological record, it is when did we first start seeing cast platinum jewelry.

Early 1900's the pieces were all fabricated, they were not cast.

From Ganoskin:
Quote:
In 1805 William Wollaston, an English scientist, developed a scientific process to make platinum malleable and shape it into wires, crucibles, evaporating dishes and sulfuric acid boilers. Since he never let anyone into his laboratory and never released the details of his process until after his death, he amassed a fortune by becoming the sole supplier of these products.


Again, we are referring to scientific application in the 1800s, not jewelry.

Casting platinum today is easier because of Stuller's 1978 discovery that if you add cobalt as an alloy, the platinum melts at a lower temperature and remains molten long enough to successfully fill the mold.

Using iridium as an alloy, we are still talking about a very high melting temperature:
Image


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Wed Feb 12, 2014 11:06 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Finally got to the bottom of this confusion thanks to Dr. Jack Ogden.
I asked him the question last evening.
Although casting platinum was experimentally done as long as a century ago, it was not an option for jewelry manufacturing until the late 70s.....80s. That's 1970-1980 by the way. :wink:


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Wed Feb 12, 2014 4:15 pm 
Offline
Gold Member

Joined: Thu Apr 17, 2008 1:47 am
Posts: 1350
Location: Pacific Northwest
What was the specific breakthrough that allowed this?

_________________
I just dreamed that I was a butterfly.


Top
 Profile  
Reply with quote  
 Post subject: Re: Casting Platinum
PostPosted: Wed Feb 12, 2014 7:32 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
I bet Stuller's discovery that cobalt lowered the temp and kept it molten longer was the breakthrough: 1978.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 13 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock