ALLOYS OF GOLD – WHY NOT PURE GOLD?

Pure gold, known to jewelers as fine gold, is too soft to be worn as everyday jewelry. It’s hardness and strength are not much more than lead, and as can readily be imagined, this effectively rules out its use for day-to-day wear.  It will bend quite easily and dent, scratch etc. with very little pressure. So, jewelers blend it with other metals using a technique known as “alloying”. In this process, metals such as silver, copper, nickel and zinc are mixed with the fine gold to increase its mechanical properties – in other words, to make it harder and stronger – giving it durability and wear resistance and making it more suitable for day-to-day activities.   However, fine gold is still used for ceremonial pieces used in some religions and – in some parts of the world, is worn by a bride for her dowry jewelry.  Of course, it is also cast into blocks – called bullion – for investment purposes.

The alloying technique also allows the jeweler to vary the color of the resulting alloy, giving a range of hues for yellow gold alloys and creating families of red, green and white gold alloys. A further added benefit is that as the gold content of the alloy is reduced by alloying, so is the cost, making jewelry more affordable to the buying public – you. But, the jeweler cannot add any amount of alloying elements to his mix. There are very strict rules governing this.

The Karats of Gold

The different levels of gold allowed in alloys are measured in “karats”, the origins of the name coming from old history when the weight of the gold was compared to a specific number of carob beans. Each karat is a weight measure of fine gold present in the alloy equal to 1/24th. So, 14K is 14/24ths or 58.3% fine gold by weight, 18K is 18/24ths or 75% and 22K is 22/24ths or 91.7% fine gold. There are numerous qualities local to areas such as Europe and the Far East. These include 8K, 9K, 10K, 20K and 21K, but there are only three hallmark qualities recognized internationally: 14K, 18K and 22K.

Under-karating

Under-karating is when an item of jewelry is described as a particular quality, say 18K, but it does not contain the minimum amount of gold required by weight. For example, with 18K jewelry this is 75% by weight fine gold. But the U.S. allows minor variations which are supposed to take note of manufacturing errors on jewelry items.  It is slightly different for un-soldered and soldered jewelry items. This means that for an item to be legally marked as 18K, it must contain a minimum of 74.7% by weight fine gold if it has no solder joints, and 74.3% by weight fine gold if it has a solder joint.

The Wedding Ring Workshop Quality Assurance

Rest assured that all Wedding Ring Workshop jewelry is guaranteed to meet a minimum of 75% by weight of fine gold if it is marked 18K. We do not take allowance of the negative assay tolerance.  

Weight vs Atoms

When weighing the advantages of one quality over another – for instance “is 18K really that much better than 14K?”, you must not only take into account the weight of gold present in the jewelry, you also need to consider “atoms”. True, there is more gold by weight in an 18K wedding ring than the same ring in 14K, but there are also other important factors to consider. All matter is made up of atoms. For each different element, the atom is a specific size and a specific weight. So if we remember our math, we take the weight of the metal and divide it by the volume it occupies, giving us a result called the “density”, sometimes also called “specific gravity”.

Why is This Important?

This is important when we consider gold alloys in jewelry. If you choose a 14K gold ring, 58.3% of the weight of the ring is gold, with 41.7% comprising the other alloying metals, usually silver and the base metals copper and zinc. This seems good, since more than half the weight is gold, but because of the high specific gravity of gold compared to these other metals – each different atom being similar in size but weighing much more – the actual number of gold atoms present is much less. For a 14K yellow gold alloy, only about 30% of the atoms are gold.  With 18K gold, this number increases significantly. We know that 75% of the weight is gold but, also, at least half of the atoms are gold, or over 50% of them. So 18K gold is a true “gold alloy” with more atoms of gold present than everything else added together.

Coming Next – Different Colors of Gold

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