[Jewelry making - Article 00100] - Re: [Orchid] Platinum rings - which alloy is best?

[Matthias Fehlinger]

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Hello Keo,

    two years ago I purchased a pair of 960/40 Pt/Cu wedding rings here
    in Germany and I want to tell you a bit about the characteristics.
    Maybe you take a trip or order them here, if you hear about the
    facts? 

>     However, upon closer studies on this issue on the web, it seems
>     platinum is generally softer than gold and is, as you describe, not
>     scratch resistant in any extent - it only moves around the scratch,
>     whereas a scratch on gold will behave differently. The rings that I
>     inspected at the shop did not look very scratch resistant at all. 

    Yes, the platinum rings are not scratch resistant. But every type of
    gold ring will do the same. The difference between gold and platinum
    alloys is: platinum moves around (you were right about this) and gold
    will loose weight. 

    In fact, all the scratches on our rings add up and give some type of
    matte finish. We think it looks very fine. I would like to add, it is
    impossible to produce a ring that will keep a mirror finish over a
    period of more than some months. 

    My rule of thumb is: Mirror finish gets duller, matte finish gets
    brighter when a ring is worn on a daily basis. 

>     Upon closer inspection it clearly read Pl 950. And they said
>     plat.price was 5 times higher than gold etc. I didn't feel really
>     confident by their statements. 

    In January, here in Germany platinum price was 2.3 times higher than
    750/1000 gold. 

>     I'm trying to avoid alloys mixed with non-plat. family, such as
>     cobalt, copper etc. 

    Why? Copper makes it a lot stronger, cobalt even more! 

>     My idea is that a hand made/welded plat. jewelry is stronger than
>     the factory produced, casted ones. This has lead me thinking that
>     even 999 parts or 1000 parts platinum that has been hand welded
>     (I'm not familiar with the technique at all!) can achieve some high
>     HV. 

    No. After welding, the rings get soft. It is crucial that after
    welding, the rings must be cold worked to get strong enough. 

    Now for some facts about Pt alloys. According to my informations: 

    999/1000 Pt reaches 80 HV when 50% cold worked. This is not
    sufficient for jewellery pieces like rings. 

    960 Pt/Cu reaches 180 HV when 50% cold worked.
    950 Pt/Co reaches 220 HV when 50% cold worked.

    You see: There are improved alloys compared to those they want to
    sell to you. 

Hope this helps!
Matthias

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