Properties of 9ct vs 18ct gold

[roz]

Hello!

I mainly work with sterling silver, but have one piece I make from 9ct gold. I have had a customer ask me specifically whether 9ct or 18ct is 'harder' or 'stronger' than the other. There is some very opposing information about this online, with most sources saying 9ct is harder due to the added metals to the soft gold, but others saying this is a myth, and referring to the Vickers scale.

Can anyone elaborate based on their hands on experience?

[Dennis]

Hi Roz,
The difference in hardness is really just academic. Both will give many years of faithful use, provided they are not worn for vigorous work, or in contact with abrasives such as sand or earth, and more so for 9ct, strong chemicals. See the post below.

The difference is more aesthetic. 18ct yellow or rose remain bright, whereas the same in 9ct can tarnish and become dull.
Most 18ct white is actually rather dull and grey, whereas 9ct white is bright with a yellow cast, which I find attractive,Dennis

[roz]

Dennis, thanks so much! That was sort of the conclusion I had come to but it's a difficult one to explain when they're asking specifically! Part of the reason they ask is because the item has some thin pieces so I think they have durability on their mind. I think they will also be interested in the tarnishing qualities though I really like the soft gold colour of 9ct gold, but see why people would go for a higher purity.

[CJ57]

I’ve been wearing my 9ct gold wedding ring for nearly 30 years and it’s never tarnished. I’m not sure a woman’s wedding ring ever gets a chance from being in dishwater or gardening and making jewellery. Women who lunch as I call them might be another matter but then I guess they wouldn’t look at 9ct I’ve checked and the ring I wear next to it is 18ct and I think I prefer the colour of the 9 though