Before platinum can be used in jewelry making, it has to be alloyed to create the metal most suitable for a specific application. Platinum can be alloyed with a multitude of metals to create a harder, more usable alloy. Platinum alloys range in purity from Pt 950 to Pt 900 and Pt 850. Pt950 contains 950 parts per 1000 of platinum and 50 parts per 1000 of another metal. Pt900 contains 900 parts per 1000 and 100 parts of one or more other metals. Pt 850 is not very common and is usually found in chain product.
Alloying platinum with different metals creates a variety of properties that make platinum extremely versatile. Adding five per cent ruthenium creates an alloy suitable for machining and faceting on a lathe. Many wedding bands are made this way. A five per cent addition of cobalt to platinum creates a very fine casting alloy. This alloy is hard and strong, yet very fluid and capable of filling very fine detail during the casting process. Adding tungsten will create a springy alloy that is generally used for findings. There are many more specialty alloys on the market, not to mention proprietary alloys that manufacturers create to make jewellery such as tension rings.