Pure gold makes a poor material for the crafting of jewellery. It is one of the softest metals known to humankind, and can be easily scratched or deformed with very little pressure – this makes it extremely unsuitable for the crafting of jewellery which needs to stand up to the rigours of daily life.
This softness has led to the creation of various different alloys which mix pure gold with other metals to make the resulting alloy stronger or to change their properties in other ways. Different alloys have been popular during different periods of history, so the purity of gold used in a piece can often help you to identify its age.
What is a Carat?
The purity of gold in a given piece is described in carats (spelt karats in America) which was originally derived from the weight of carob beans. These beans were used as the standard for weighing precious materials.
Carats are also used to designate the size of gemstones by weight, but in gold they have taken on a specific meaning which tells us the percentage of the final alloy that is pure gold.
24 Carat Gold
24 carat gold is the purest form of gold; the number indicates that 24 out of 24 parts of the metal is pure gold. Technically it is extremely rare to find gold that is truly 100% gold, but any metal made up of 99% gold can legally be labelled as 24 carat.
Jewellery is very rarely constructed from 24 carat gold as it would be too soft for the owner to wear without damaging it, however ancient craftsmen would create ceremonial or decorative items from this material.
22 Carat Gold
With 22 parts pure gold and 2 parts other metals, such as copper, 22 carat gold provides the most vibrant colour in an alloy which can be worked into jewellery. Such pieces must be intended for occasional, careful wear, or be designed in such a way that the metal is protected from damage.
As the alloy is still very soft the jeweller must avoid delicate wire work or elaborate engraving, instead creating larger, thicker areas of gold whose shape limits the amount of stress that can be applies to any point.
Before stronger, lower purity alloys were discovered it was only possible to work with this purity of gold, so older jewellery allowed for this in its construction. Rings with large central stones, for example, could not be held by modern claws as these small prongs of metal would easily bend or break and cause the stone to fall out.
Items crafted in the early Georgian period which used this metal were forced to enclose the stones almost completely in gold. The softness of the metal allowed them to press it tightly against the stone to hold it securely, but this severely limited the amount of light which could flow through it. To compensate many pieces from this era have a thin sheet of brighter metal pressed against the rear of the stone, referred to as “foil backing”. This allowed light to flow in and be reflected back out to showcase the stone’s optical properties.
18 Carat Gold
Comprised of approximately 75% pure gold, 18 carat gold preserves the colour and vibrance of purer alloys but is far stronger. The larger percentage of other metals allows the metallurgist who creates it to alter the colouration to suit the needs of the jeweller and eventual owner of the piece under construction.
18 carat gold can be yellow, rose or white, but all variants contain the same percentage of pure gold. Rose gold contains a higher amount of copper, whilst white gold contains either nickel, silver or palladium.
Yellow 18 carat gold is often used in gilding, where a layer of gold is chemically applied to the outer surface of a piece of jewellery. If a higher carat gold was used for this process the treatment would easily wear away. This is not to be confused with gold leaf, where extremely thin pieces of gold foil were applied to the surface of pieces of artwork. Although pieces treated with gold leaf are undeniably beautiful they are also extremely fragile.
15 Carat Gold
In the latter half of the Georgian period stronger 15 carat gold began to be used as jewellers experimented with more elaborate metalwork. Wire work in particular required stronger metals, and this alloy granted these craftsmen greater flexibility.
Advances in machinery and the technology of metalworking allowed this stronger alloy to be worked more effectively, and it was so popular that in 1854 (the early years of the reign of Queen Victoria) 15 carat gold became the official gold standard across the British Empire.
As this alloy was so much more durable than those which came before jewellers were now free to create slimmed more elegant chain links and wire work, as well as engravings which would be able to withstand wear for longer. This is why Georgian jewellery is often thicker and more substantial, whereas Victorian and Edwardian jewellery is finer and slimmer.
15 carat gold also allowed jewellers to secure precious stones with small claws, which allowed more light to flow through them. This, coupled with advances in the cutting of gemstones, made the subsequent era’s jewellery much brighter.
14 Carat Gold
Although 15 carat was the standard during the height of the British Empire the rise of America as a world power after the first world war meant that the newer nation took the lead. When American jewellers began using 14 carat gold as standard much of the rest of the world followed suit. Consequently much of the jeweller created between the world wars was 14 rather than 15 carat, and jewellery crafted in 15 carat gold became much rarer.
9 Carat Gold
9 carat gold is typically the lowest purity used in fine gold jewellery creation. It contains 37.5% pure gold, making it the strongest. As it has a high percentage of other metals it varies in colour depending on where it was made and by whom.
Although 9 carat gold is less expensive than the higher carats it has been used to create some truly wonderful pieces, including a great amount of fine antique and vintage jewellery. 9 carat jeweller has the advantage of being extremely sturdy, holding its shape and any precious stones more securely than higher carat weight.
Which gold purity is right for me?
All gold alloys have their strengths and weaknesses. When choosing what purity of gold you would like it is important to know how you intend to use the piece of jewellery in question. Anything which you intend to wear every day should be as strong as possible whilst maintaining the colour that you want. The same is true of extremely fine and delicate designs – a heavy gold chain is still relatively tough when crafted in 18 carat gold, but an extremely slim chain would be susceptible to damage and is probably better suite to 9 carat.
It can be confusing to attempt to choose a particular purity of gold for your jewellery. Luckily at Antique Jewellery Online we have a team of highly experienced and friendly staff who will be happy to discuss what would work best for you.
We look forward to hearing from you!