A Guide to Metals
9 Carat versus 18 Carat Gold
Most people have always believed, or been told, that 9 carat gold is harder, or harder wearing, than 18 carat gold. This is not true … as 9ct gold has less parts of pure gold in its makeup (only 9 parts out of 24 parts of pure gold – 18ct gold has 18 parts out of 24). It is also much less resistant to chemical attack in normal use than 18ct gold. 9ct alloys will go dull or even black merely from exposure to certain chemicals in the atmosphere. They will also discolour in contact with perspiration, chlorine in swimming pools, medication taken by the wearer, bleach and other household chemicals. 18ct Gold contains twice as much gold as 9 carat which makes it more expensive … but in terms of durability and performance – including a resistance to corrosion – 18ct gold has such excellent all round properties that it can be declared the best gold alloy standard for fine jewellery.
White Gold versus Platinum
Did you know that 18 carat white gold is 75% pure yellow gold? The colour is changed to white gold by adding alloys (25% of the total mix) and coating the jewellery with bright white rhodium. The quality of white gold is determined by the choice of alloys used to alter the colour. When the rhodium plating begins to wear (approx 6-12 months) the true colour of the gold is revealed. If the gold has been mixed with nickel, the white gold will appear quite yellow. If mixed with platinum and palladium alloys, the white gold will appear much whiter and brighter, hence requiring less maintenance.
Platinum is the rarest and most valuable of all precious metals. It is a pure and natural white alloy and weighs approximately 50% more than gold. It does not fade, or tarnish and it is hypoallergenic. The premium quality platinum used in jewellery should be 95% pure for strength and durability. Platinum settings do not require rhodium plating. Platinum is a denser metal which maintains its integrity over time above and beyond other metals.
Palladium versus Platinum
A platinum family member, palladium is rich in lustre and has a slightly different shade of white to its sister platinum. As platinum, palladium requires no rhodium plating. This rare white metal has been found among early Egyptian artifacts, but it is only in the last few years that it has rapidly gained recognition for us use in fine jewellery. As strong and as naturally white as Platinum; Palladium is durable and will last forever. The premium quality palladium used in jewellery should be 95% pure for strength.
Platinum jewellery contains more fine metal than most other jewellery, being at least 95% pure. This rich purity makes Platinum hypoallergenic, and its natural white colour will not tarnish or lose its lustre. One of the strongest metals used in jewellery, Platinum will endure through all uses. It will resist wear even after a lifetime of use and is one of the best precious metals for setting gemstones and diamonds.
The main differences between palladium and platinum are colour, density – palladium is a lot lighter than platinum and price per gram – palladium is cheaper than platinum and weighs less. Palladium is also not yet widely used for setting gemstones and diamonds – although it is a suitable metal for that use.