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Do you know how much of precious metal is in your watch(es)? Read this
All that glitters may not be gold
By KELVIN LEE
SOLID gold watches are sometimes offered by watchmakers as encasements for their finer movements, or as luxury alternatives to stainless steel. Gold watchcases usually come as yellow, white, rose (or pink) gold and in one of several possible purity levels. The amount of gold within is referred to as 'karat' or 'fineness'. Pure gold is 24 Karat (K), or .999 fine on its purity scale.
Higher purity is not necessarily better, as pure gold is too soft and malleable for making watchcases. Even 22 karat gold, containing 91.8 per cent gold content mixed with other metals is too soft. The most commonly used purity of gold hard enough for daily wear is 18K. Older gold watches, mostly before the 1970s, are often seen in purity levels ranging from 9K to 14K. Generally, only watches marked as 10K and above are allowed to be sold as solid gold watches.
A quick guide to gold content commonly used in watch cases:
18K - 75 per cent
14K - 58.5 per cent
12K - 50 per cent
10K - 41.7 per cent
9K - 38 per cent
Golden rainbows
Gold alloys are sometimes mixed with small amounts of silver and copper. The percentage alloyed determines its colour and hardness. A small amount (0.2 per cent) of zinc can also be added to harden the alloy. An equal ratio of silver and copper gives gold the yellow hue we are accustomed to seeing. When more silver is used, the result is slightly greener and when more copper is used the gold has a richer red colour.
White gold is made when gold is alloyed with nickel or palladium, rather than silver and copper. Harder wearing than yellow gold, it polishes beautifully. White gold cases are sometimes plated with rhodium for even harder wearing characteristics. Care should therefore be taken not to use household metal polishing chemicals to buff white gold cases, as it may damage the rhodium.
Another commonly used type of gold in watchcases is 'rose gold'. There is no single recipe, and variations abound. For example, the highest karat version of rose gold is 22K, and also known as 'crown gold'. In the Middle East, a 'red gold' is often found in 14K purity which is 42 per cent copper.
The most common purity of rose or pink gold found in watchcases today is 18K. This consists of 75 per cent gold, 21 per cent copper and 4 per cent silver. Common wisdom is that contact between rose gold and some compounds such as chlorine (from water) and alcohol (perfume) should be minimised, as this reacts with the rose gold.
Rolex uses a slightly less red version of rose gold which they call 'Everose'. A little platinum is added to the mix to improve resistance against corrosion and tarnish.
Yellow outside, white inside
Where gold is too expensive, the most commonly used method of adding a gold lustre to a watch case is gold plating. This is sometimes marked as 14K or 18K GP, depending on the purity of gold used. An electrical process, a piece of base metal (normally brass) is typically plated with between 1 and 20 microns of gold in a plating solution.
Less commonly used these days but more durable, is gold-fill. Also known as rolled gold or RGP, this process involves a very thin sheet of gold being fused to a lesser metal (usually brass) under heat and pressure. Gold-filled watches are sometimes marked as 'GF', inserted after the purity of gold used, for example, 14K GF. Compared to gold plating, gold-filled watches and jewellery have more gold and have much longer lasting gold lustre if heavy wear or chemical contamination is avoided. Both options provide the look and feel of gold at a fraction of the price.
A watchmaker once told me that a rule of thumb for checking if a gold watch contains only solid gold is by looking at the back case. Watches which are gold plated or gold filled often have steel back cases. If buying a gold (or precious metal) watch, you should also plan to examine the hallmarks on the watch case and bracelets. These are marks guaranteeing the purity or fineness of the metal as determined by formal metal (assay) testing.
The Swiss system of hallmarking was introduced in 1881. Under current laws, all gold, silver, platinum or palladium watch cases made in Switzerland or imported into Switzerland are affixed an official Hallmark; the head of a Saint-Bernard dog. This is near another Maker's Responsibility Mark and the indication of purity. Hallmarks are often found on the watch's mid-case between the lugs or on the lugs themselves, with the back case having its own hallmarks.
Do note however that various hallmarks have varied over time, across different countries and with different watch makers. A bit of research will be required to determine if a hallmark is correct and if it is authentic.
The Business of Time
Published August 26, 2011
Do you know how much of precious metal is in your watch(es)? Read this
All that glitters may not be gold
By KELVIN LEE
SOLID gold watches are sometimes offered by watchmakers as encasements for their finer movements, or as luxury alternatives to stainless steel. Gold watchcases usually come as yellow, white, rose (or pink) gold and in one of several possible purity levels. The amount of gold within is referred to as 'karat' or 'fineness'. Pure gold is 24 Karat (K), or .999 fine on its purity scale.
Higher purity is not necessarily better, as pure gold is too soft and malleable for making watchcases. Even 22 karat gold, containing 91.8 per cent gold content mixed with other metals is too soft. The most commonly used purity of gold hard enough for daily wear is 18K. Older gold watches, mostly before the 1970s, are often seen in purity levels ranging from 9K to 14K. Generally, only watches marked as 10K and above are allowed to be sold as solid gold watches.
A quick guide to gold content commonly used in watch cases:
18K - 75 per cent
14K - 58.5 per cent
12K - 50 per cent
10K - 41.7 per cent
9K - 38 per cent
Golden rainbows
Gold alloys are sometimes mixed with small amounts of silver and copper. The percentage alloyed determines its colour and hardness. A small amount (0.2 per cent) of zinc can also be added to harden the alloy. An equal ratio of silver and copper gives gold the yellow hue we are accustomed to seeing. When more silver is used, the result is slightly greener and when more copper is used the gold has a richer red colour.
White gold is made when gold is alloyed with nickel or palladium, rather than silver and copper. Harder wearing than yellow gold, it polishes beautifully. White gold cases are sometimes plated with rhodium for even harder wearing characteristics. Care should therefore be taken not to use household metal polishing chemicals to buff white gold cases, as it may damage the rhodium.
Another commonly used type of gold in watchcases is 'rose gold'. There is no single recipe, and variations abound. For example, the highest karat version of rose gold is 22K, and also known as 'crown gold'. In the Middle East, a 'red gold' is often found in 14K purity which is 42 per cent copper.
The most common purity of rose or pink gold found in watchcases today is 18K. This consists of 75 per cent gold, 21 per cent copper and 4 per cent silver. Common wisdom is that contact between rose gold and some compounds such as chlorine (from water) and alcohol (perfume) should be minimised, as this reacts with the rose gold.
Rolex uses a slightly less red version of rose gold which they call 'Everose'. A little platinum is added to the mix to improve resistance against corrosion and tarnish.
Yellow outside, white inside
Where gold is too expensive, the most commonly used method of adding a gold lustre to a watch case is gold plating. This is sometimes marked as 14K or 18K GP, depending on the purity of gold used. An electrical process, a piece of base metal (normally brass) is typically plated with between 1 and 20 microns of gold in a plating solution.
Less commonly used these days but more durable, is gold-fill. Also known as rolled gold or RGP, this process involves a very thin sheet of gold being fused to a lesser metal (usually brass) under heat and pressure. Gold-filled watches are sometimes marked as 'GF', inserted after the purity of gold used, for example, 14K GF. Compared to gold plating, gold-filled watches and jewellery have more gold and have much longer lasting gold lustre if heavy wear or chemical contamination is avoided. Both options provide the look and feel of gold at a fraction of the price.
A watchmaker once told me that a rule of thumb for checking if a gold watch contains only solid gold is by looking at the back case. Watches which are gold plated or gold filled often have steel back cases. If buying a gold (or precious metal) watch, you should also plan to examine the hallmarks on the watch case and bracelets. These are marks guaranteeing the purity or fineness of the metal as determined by formal metal (assay) testing.
The Swiss system of hallmarking was introduced in 1881. Under current laws, all gold, silver, platinum or palladium watch cases made in Switzerland or imported into Switzerland are affixed an official Hallmark; the head of a Saint-Bernard dog. This is near another Maker's Responsibility Mark and the indication of purity. Hallmarks are often found on the watch's mid-case between the lugs or on the lugs themselves, with the back case having its own hallmarks.
Do note however that various hallmarks have varied over time, across different countries and with different watch makers. A bit of research will be required to determine if a hallmark is correct and if it is authentic.
The Business of Time
Published August 26, 2011
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