The Main Differences Between 9ct and 18ct Gold.
Fine gold content:
• 18 carat gold contains twice as much fine gold by proportion (750ppt vs 375ppt)
• 18 carat gold is approximately 40% heavier.
• 18 carat gold contains over 2.6 times as much fine gold as a 9 carat product of the same size/volume. That is to say, don’t expect that if you have two identical items in 9 and 18 carat gold, the 18 carat one has twice as much gold, this is not the case.
• Tarnish resistance – 18 carat gold is more resistant to tarnishing and other chemical attack than 9 carat gold. This is because silver and copper, which constitute a larger proportion of 9 carat gold, oxidises more readily than gold.
• Hardness – An issue on which there is much discussion. It is often claimed that 9 carat gold is harder than 18 carat, but this does not mean it is more durable. Gold rings can give many years of wear – a ‘soft’ 22 carat ring can easily last for more than 50 years, and the wearer can appreciate the fine colour and lustre of almost fine gold for the whole of that time!