how do i check if its platinum

Discussion in 'Platinum' started by purgatori, Feb 11, 2012.

  1. purgatori

    purgatori New Member

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    hi all i was just wondering if there is away i can test a ring to tell if its platinum without sending it to a jewler
    its stamped 900 and other markings but they are to worn to tell what they are
    any help would be good thanks
     
  2. THUCYDIDES79

    THUCYDIDES79 New Member Silver Stacker

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    Do a specific gravity test.

    Pure platinum is around 21

    Since it is 0.900 than the remaining 10 % is mixed with either

    a. gold ( around 19.5 )
    b. silver ( around 11 )
    c. base metals ( 7 - 9 )

    calculate the specific gravities of a,b & c and compare it with ur measured specific gravity
     
  3. Water&Food

    Water&Food New Member

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    THUCY, not quite. Platinum is normally plated with Rhodium buddy to give the article extra mirror shine.

    Anyway, the most popular Alloy for Platinum is Palladium (helping to make Pt more ductile to work with).

    What is strange is the 900 Hallmark. 950 is the most popular purity for Platinum. If it is real Platinum, this leads me to believe the Jeweller is not well known and is possibly a hobbyist, since he/she lacked tools and technique to effectively work with 950 Platinum.
     
  4. silverstar1

    silverstar1 New Member

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    Actually Platinum is not usually plated with rhodium, white gold is usually plated with rhodium because white gold is still usually a bit yellow and gets more so in time. There would be no point in plating PT(platinum) or PD (palladium) with rhodium, platinum polishes just fine. Also the most popular alloy for PT is NOT PD , I have heard of it but PT PD alloy but it is rare and is usually 900. 900 PT is actually quite common 900 is usually alloyed with 10% Iridium ( and there is always usually small trace elements which make alloys temperment , colors and polish vary ever so slightly) the other most common and more popular is 950 PT which is usually alloyed with 5% ruthenium or irridium . There is no different tools or techniques that are any different from 900 to 950 PT , just make sure to wear your dark welding goggles if you are going to be melting any. So if you are doing a SG test I would use irridium as the other 10% and I do not know the SG off hand. I hope this claifies this for anyone that actually cares.

    PT900 (platinum irridium) alloy density 11.349 troy oz per cu. in.
     
  5. THUCYDIDES79

    THUCYDIDES79 New Member Silver Stacker

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    Even if it were plated with Rhodium, the weight of the Rh would be negligible in comparison to the weight of the object being examined.

    the specific gravity of the 0.900 Pt object should be at least around 18
     
  6. silverstar1

    silverstar1 New Member

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    Do you know the specific gravity for iridium?
     
  7. purgatori

    purgatori New Member

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    it was made in the 1920s its not a late ring
     
  8. hiho

    hiho Active Member Silver Stacker

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    well in my game platinum/platinum-rhodium Resistance Temperature Devices [RTD] are used for thermal measurement offering 100ohm resistance at 20 degrees celsius, they are used for processes such as steam, pregnant liquor solutions, acid etc

    They are deemed highly accurate and very expensive when you have an 1.5mm compensation wire 20-30m long
     
  9. camylopez

    camylopez Member Silver Stacker

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    You should be able to tell the difference between plat and other metals just by picking it up, plat will be a lot heaver than what you would be used to if it were gold or silver. I have also come across 900 silver a fair bit, so silver is also an option, however doesn't sound like anything else so it would be one of those two.
    Please also bear in mind, that if you are doing gravity test, make sure no air pockets, shake any air bubbles out, I have seen big variances on this test if not testing solid pieces.
     
  10. purgatori

    purgatori New Member

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    thanks all
    heres the ring its been on here before and i want to get it fixed and if its platinum its going to cost $900 to fix
    [​IMG][​IMG]
     
  11. camylopez

    camylopez Member Silver Stacker

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    looks silver to me
     
  12. Water&Food

    Water&Food New Member

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    True. I only speak from some buddies telling me. Depends on country and jeweller. I preferred Pt/Pd myself.

    Anyway, just to clarify, Rhodium plating popular on articles desiring extra shine and durability.

    johnsonmattheyny.com PDF
    Here in Australia 950 Pt is the most popular.
    .
     
  13. Water&Food

    Water&Food New Member

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    silverstar1, helps to give sources. Also helps if others know your background (other than Google). Hence, "John Galt".
    Cheers.
    .
     
  14. Water&Food

    Water&Food New Member

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    Under 2.5 grams of additional Platinum + under 30 minutes labour time = $900 rip off.
     
  15. THUCYDIDES79

    THUCYDIDES79 New Member Silver Stacker

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    The difference between pure gold and pure platinum would not be easy to feel in the hand with smallish objects.

    Pt is around 10% denser than Au.

    Pt and Ag is easy to tell apart by picking it up.

    A 1 oz Pt coin which has the same diameter as a 1 oz silver coin will have HALF the thickness.
     
  16. silverstar1

    silverstar1 New Member

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    Seeing the picture now this is kind of a stumper. From the inside of the shank it does look like silver but I think it is just the lighting. The top does look like a platinum alloy espescially if it is really that old because any silver from that time period unless it had been thourughly cleaned would have tarnish in the crevices and it does look alot like some of the alloys back in that time period, real grey and brittle. The best way at this point i would say is the SG test or if you hold a peice of silver of similar size the weight difference will be very noticable with platinum.
     
  17. silverstar1

    silverstar1 New Member

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    The source is me , and i dont think you will find me on google, there may be a silverstar 1 but it is not me. Yes I think $900 to replace the shank on this is a little much as well.
    W&F I hope you are not still sore at me for asking to buy opals from you!
    Cheers
     
  18. camylopez

    camylopez Member Silver Stacker

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    An easy to clear this up, go down to your local GB kiosk, (Their in most shopping centers these days) and ask them to do a scratch test. They will tell you they cant test plat or silver, and they prob wont know anything. However just watch them, and ask them to test with 18k acid, and 22k acid.
    If the 18k acid melts the scratch and comes back a blue color, your looking at silver.
    If 18k doesn't melt the scratch, but 22k does, then your maybe looking at a white gold alloy, though it doesn't look like it. But please wait 10 to 15 seconds for it to melt as 900 is quite high.
    If neither acids make any impact, then your most likely looking at platinum.

    I agree about the tarnish, however the weird thing is I have seen quite a bit of old silver stamped 900, but with no tarnish on them. Usually from some european country, Ive had most commonly seen it on german silver.
     
  19. LTEK4NZ

    LTEK4NZ Member Silver Stacker

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    .900 could be coin metal people used to melt their money into jewelery and service wear. if they had that much coin to spare. you still see some items at IRL auction houses that are listed as say"silver coin cutlery." or "coin metal vase"
     
  20. Water&Food

    Water&Food New Member

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    No buddy.
     

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