Ever wondered what exactly do terms like 916, Hallmark, KDM, mean? Here we explain these terms and also the basics of gold jewellery making.
This is quite simple, 916 represents the finesse of gold jewellery – 91.6 gms of gold per 100 gms. The figure 916 denotes 22 carat (22 ÷ 24 = 916). And if you are wondering why not make jewels in pure gold, pure gold is too soft to be made into wearable jewellery. There are some 99% pure jewellery made with special alloys, but delicate workmanship & intricate designs are not possible in pure gold.
Hallmark is a sure way to be assured of the quality of the jewels you buy. Every jewel that has been hallmarked is tested for purity at an BIS authorised assaying centre and once it passes the check, a laser engraving is done to identify the jewel. A hallmark seal consists of five parts as in the image above. Next time you buy a jewel make sure to check for all the five seals as above.
Good to know
- All our Jewels including coins are Hallmarked.
- Apart from 916 (22 carat), Hallmark is also offered for 23 carat (958), 21 carat (875), 18 carat (750) purities. The purity of a jewel will always be mentioned in the Laser engraving of a Hallmark seal.
Ever heard about KDM & Non KDM jewellery? So what does KDM jewellery mean? Before talking about KDM, we will tell you about jewellery making in short. The basic process in jewellery crafting is soldering a myriad of intricate gold parts. Without soldering, there is hardly any jewel that can be done. Needless to say this solder should have a melting temperature lower than that of gold, so just the solder melts and joins gold pieces without affecting the gold parts. Earlier this solder was a combination of Gold & Copper. Though there was no particular ratio for this solder, generally it was about 60% gold + 40% copper. Since this alloy was very strong and also easy to make, it was widely used in jewellery making for a long time. But the downside to this solder is that, the purity of the solder is only 60%. So when this jewel is melted, the quality will be less than 22 carat. This is the reason your old jewels may carry an seal of 22/20 (20 carat represents the melting purity).
To overcome this problem and maintain a high standard of gold purity, cadmium began to be used in place of copper. The advantage being that unlike the traditional gold & copper solder, gold and cadmium can be mixed in a ratio of 92% + 8%. In other words the solder itself has a purity of 92%. This ensured the finesse of jewel remains constant regardless of the amount of solder used. Such jewellery using cadmium began to be widely known as KDM jewellery.
But shortly after the introduction of cadmium, it was banned by BIS as it was found to cause health issues for artisans working with it. After the ban, cadmium was replaced by advanced solders with Zinc and other metals. But the term “KDM” hung on and is still commonly used. So a KDM jewellery means it will have the same purity even when it is melted, as the solder itself has a purity of 92%.
Now that you have known about Hallmark, 916 & KDM, why not browse our unique collections of Hallmarked jewellery?