This is a brief explanation of the colour and purity of gold and platinum metals which are regularly used in our wedding rings and apply to the UK in particular.
Two terms are used in jewellery to signify the fineness of the gold and precious metal alloys, they are “carat”; an ancient measurement expressed in 24 parts, and a modern European “millesimal” measurement expressed as parts per 1000.
The original “carat” or (ct) remains widely understood as the most recognisable term of gold fineness. However the millesimal value is used on all current UK hallmarks. For example, 18ct or (750) gold is 18 parts pure gold 6 part alloys or 75% pure gold to 25% alloys.
24ct (999.9) = pure gold which is too soft for general jewellery use. It is golden yellow in colour. All gold jewellery is made from alloys of pure gold with different metals added to produce alternative colours and working characteristics.
The metals most often used as alloys with gold are palladium, silver and ruthenium for white colours and copper, silver and zinc for red colours.
18ct (750) available in a deep yellow colour, greyish white colour and strong red colour. This is generally the purest form of gold used to make shaped wedding rings. It stands up to everyday wear very well, showing very fine surface scratching which does not detract from the ring design. We use a high palladium alloy of 18ct white gold which continues to look good even as the rhodium plated surface begins to wear away.
9ct (375) available in pale yellow colour, white colour and strong red colour. This is the most popular grade of fineness in the UK.
It is very affordable and looks good when new. Its wear characteristics are not quite as good as higher carat golds, showing signs of scratching and wear within just a few years.
White gold tends to be a little softer than the yellow and red versions. The difference in the colour of the white alloy compared to the rhodium plated surface is more noticeable as the surface begins to wear.
As all white golds are either slightly grey or brownish grey in colour it has become common modern practice to electro- plate these alloys with rhodium, a metal which produces a very highly reflective, perfectly white surface colour which normally lasts 1 to 2 years.
Platinum (950) is 95% pure platinum and 5% alloys, cobalt or ruthenium. It has a clean grey/ white colour. It is a very dense metal which feels noticeably heavier than all other precious metals. Platinum has the very best wear characteristics. It shows very fine surface scratching which does not detract from the design. It is very malleable, tending to be forgiving rather than show signs of wear and it will last for many years.
It is one of the most resistant metals available and will not be affected by salt water or chemicals. Its ductility makes it perfectly suited to accept diamond setting.