Platinum Durability and Scratching

One of the most frequently asked questions about Platinum concerns scratching.  It seems that the consumer equates durability with scratch resistance and is then disappointed when Platinum jewelry scratches and show signs of wear.

Let me say that all metal scratches.  From the finest steel to the finest Platinum, no metal is immune to scratching.  When two materials come into contact, the harder one will always prevail. Whether you use a kitchen utensil or a wrench while wearing a platinum ring, a scratch will result if contact is made.  The same is true for door hardware, garden tools and any other item that is harder than Platinum.  Since these are the objects that we come into contact with each day and impart scratches, the Platinum will develop a patina-like appearance that will last.  This is also the reason why many designers prefer satin finishes, brushed and sand-blasted finishes over the bright polished look.

There are, however different alloys that have a different hardness and thus a greater scratch resistance.  This does not mean that any of the alloys are completely impervious to scratching, it only means that some alloys have somewhat more resistance to scratching.

Another point to keep in mind is that there is a difference between strength and durability.  Strength is measured in pounds per square inch (PSI) and scratch resistance is determined by hardness.  The following is a comparison of some Platinum alloys:

Platinum 900 Iridium               110HV*           55,000PSI
Platinum 950 Iridium                 80HV             40,000PSI
Platinum 950 Cobalt                135HV             64,000PSI
Platinum 950 Ruthenium       130HV             66,000PSI

*The hardness of these alloys is measured in Vickers Hardness (HV) and this value is not indicative of the strength of the material.

As you can see, Pt/Ru has the most tensile strength, whereas Pt/Co has the highest scratch resistance.

When discussing the relative strength there is also the subject of specific gravity that plays a role in the care and handling of Platinum.   This material is much more dense than other precious metals and therefore if a ring made of Platinum is accidentally dropped, even from waist height, it will have a tendency to deform somewhat.  This will be true of very light and open work pieces as well as the much heavier and thicker bands due to the high mass.  This sort of abuse can be particularly troublesome if the ring has stones set into the shank such as channel set, burnished or baguettes.  In such a case, a major repair may be necessary.  Platinum clients should be made aware of these properties and informed as to the proper care of fine jewelry made from Platinum.

To further clarify, there is a major difference between durability and scratch resistance.  Platinum is very durable.  When scratched, the scratch will actually displace the metal, leaving ridges on the edges of the scratch.  This is where durability comes in. whereas other precious metals, if scratched, lose metal, and thus wear down, Platinum does so at a much slower rate.  This is why finishes on other precious jewelry wear off, prongs wear down and the rings actually become thinner and even wear through in time.  Because many gold products, white or otherwise, are plated, and the plating creates a hard skin, they sometimes seem to have more scratch resistance than Platinum.  You will find that soon the plating will wear off and the material will again scratch with daily wear.

With Platinum, this is a different story.  Many pieces from the turn of the century have engravings that look as good as new, beads that hold stones appear to have just been made and the overall signs of wear seem insignificant on these pieces of Platinum jewelry.  A Platinum wedding band will last a lifetime.

Polished Platinum, especially the iridium alloys, will display a bright natural white color. In spite of daily wear and scratching, the finish will endure for a very long time.

Make sure to check out our Jewelry Casting section for more information about our casting services. If you have any questions concerning the above suggestions, or we can help you with any piece, please contact us. We will be happy to assist you.