Does 9 carat gold last longer than 18 carat gold?
It’s surprising for most people to learn that the answer is NO.
It would be fair to assume that this confusion has arisen due to the fact that pure gold is known to be quite soft, too soft in fact to be used successfully in jewellery. 18 carat obviously contains twice as much gold as 9 carat, the assumption being that it is therefore softer.
Also, it is widely known that if gold is alloyed with other metals it becomes harder, however, many people assume that the more other metals are added the stronger and harder the resultant alloy.
There are many different combinations of metals which can be used to make gold alloys with each combination having specific characteristics. This can be further influenced by mechanical working and appropriate heat treatments; however in general most common 18 carat gold alloys are both harder and more hard wearing than their 9 carat equivalent.
| Alloy | Hardness | Max. Annealed Hardness |
| 9 ct Gold | 70 – 105 | 160 – 170 |
| 18 ct Gold | 85 – 125 | 170 – 230 |
A simple table comparing 9 carat and 18 carat gold using the “Vickers” hardness test.
The “Vickers” hardness test method consists of indenting the test material with a diamond indenter then establishing the relationship between the load applied and the area of indentation. A little scientific perhaps, and not easily achieved at the jewellers workbench.
