What is a Gold Alloy?

Alloying refers to the mixing together of two or more metals and is usually done to improve the mechanical properties of the metal.  Mechanical properties refer to how much you can bend, stretch, scratch or break a particular metal or allow.  Jewelry metals like gold, silver and platinum are relatively soft in their pure form, so the wear and tear they would experience during day to day wear would cause your jewelry to look quite worn rather quickly.  Hence the need to develop alloys for use in jewelry production.  The science of metallurgy is quite complicated, so for our purposes the alloying practices we will discuss are relatively straightforward.  Many years of research and experimentation have given us specific combinations of metals that work well together and we will focus on those.

In jewelry, you will usually have a binary, two metal, or ternary, three metal, system.  In a binary system, two metals are melted together in a crucible, essentially a specialized cup made of metal or ceramic, until they are well mixed and form a homogenous mixture.  Think of it like when you bake a cake and you have to make sure there are no lumps of flour or unincorporated ingredients.  Just like baking, each element of the alloy has to be carefully weighed prior to mixing to ensure that at the end of the day, you get the right product.  The mixture is then cooled to a solid mixture and there you have it, your gold alloy.  Whether the allow is 14k, 18k or 22k gold depends on how much of the alloying metal you added.  You can refresh yourself on gold content by reading this post.  A ternary system works the same way except three metals are melted together and then cooled.  The rate of cooling, or how fast the material is cooled, has a big impact on the internal structure of the alloy and affects the mechanical properties we mentioned above.  The table below shows some of the common ternary and binary systems used in fine jewelry.  These are only a few of the possible combinations available.  White and colored gold alloys present different challenges in both manufacture and proper care and maintenance.  We will talk more about that in a future post. 

Over the years, gold refiners have developed specific recipes to help jewelry manufacturers achieve desirable mechanical and physical properties for their gold products.  In practice, when a jeweler wants to cast a new ring, he does not measure out each individual metal listed in the table above, rather he uses a “Master Alloy” purchased from a gold refiner and then adds the appropriate amount of pure gold.  An example of alloys available from Hoover and Strong is shown below. So, if you were making an 18k green gold ring that was going to weigh 100 grams, you would weigh out 75 grams of pure gold and then add 25 grams or your Master Alloy G18.  This is just an excerpt to give you an idea of what is available and is not intended to endorse one company over another.

This is a very simple overview of alloying gold.  Please contact us with any questions or if this is a topic you would like us to write more about.  Hopefully this helps you understand a bit better what you’re getting when you buy a 14k or 18k gold necklace. Now you can subscribe to our mailing list to learn more and share with your friends!