First, it's important to understand that all metals scratch. From the finest steel to the finest platinum, no metal is immune to scratching. A metal's resistance to scratching is determined by its hardness. As a result, tempered steel is less likely to scratch than softer precious metals.

A metal's tendency to scratch can be assessed by measuring the time it takes for a polished sample to lose its reflectivity when exposed to abrasive media under controlled conditions. This information is available for most common platinum alloys, and can be used to determine the best alloy choice for a particular job. (See "Comparison of Common Platinum Alloys" chart.)
 

Another relevant measure hardness, measured in Vickers (HV). Vickers is a means of determining the hardness of a metal by pushing a pointed object into the surface of the metal with a determined load and then measuring the penetration. The deeper the impression, the softer the metal, and the more prone it is to scratching. As a rule, the harder the metal is, the more scratch resistant it is.

Hardness differs from strength, which is measured in pounds per square inch (PSI). Whereas hardness determines a metal's scratch resistance, strength determines how much force is required to make the metal deform or bend to failure.
 

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