Platinum Engagement Rings
Platinum, one of the rarest precious metals, is a white metal and does not need any colouring agent. The appeal of platinum is in its unique white luster. Around 5% of other metals are added (iridium) to give platinum better hardness and wearing qualities. Platinum has advantages over white gold, but is very expensive because it is so rare and weighs half as much again as white gold. It is mainly used on fine gem set pieces of jewelry.
While not as strong as many jewelers suggest it is, platinum is very hard wearing and clings to itself. A platinum ring will wear through any gold bands worn beside it on the same finger.
It is almost twice as heavy as 14-karat gold, which gives a “heft” to fine jewelry, which people naturally equate with value. In recent years platinum has rapidly grown in popularity. It’s become the new choice for many diamond engagement rings. It brings out the brilliance of fine diamonds better than gold.
It takes more experience and more expense to work in platinum. Gold melts at about 1,000°C, whereas common platinum mixes melt at 1,700°C – 1,800°C. It doesn’t flow as smoothly as gold due to its density so if you’re not experienced you can run into problems with porosity. Also important is that a jeweler goes through many more burs and drill bits working with platinum because of the density – so it’s more costly in terms of the actual tools themselves, not just the metal. It’s more malleable, and that’s nice when setting, but smithing and crafting take considerably more know-how and effort.
Platinum prices today are very high. To show platinum properly requires a very large investment. This investment does not turn quickly for much of the work needed is special order. With gold you can size it or switch the prongs. Platinum is a totally different animal. Because of the purity and density a platinum inventory can easily run a jeweler 3 times the cost of a gold inventory.
Different platinum alloys have different useful properties. The metals used to alloy are not usually added at 100%, but alloys themselves and different combinations yield different results.
Some variances are: casting results: (porosity, finesse, and polish ability), workability/malleability, colour, fusibility and weather it can be re-melted/refined without expensive dedicated equipment, hardness and how well it polishes and how well it keeps its polish.
Cobalt is the most common casting alloy and the results in castings are excellent. It is bluish and it oxidises, but it takes rhodium better then gold alloys and the oxidation can be removed (though not with sulphuric acid). It has a good hardness, fairly workable (though you would never use it as stock gauge metal for hand wrought pieces). It is difficulty to refine. It does not overtly soften by annealing and does not ‘work-harden’ very much. The hardness is therefore relatively stable, which suits is mass-production purpose. It lacks good colour. Cobalt is a heavy metal making 950 platinum, less platinum by volume, but it is a decent alloy and for cheaper jewellery, therefore it is a good bet.
Iridium is the best and worst alloy, with the best colour and a liquid platinum finish in harder alloy varieties. Plat 950 and pure iridium is terribly soft. What is worse is that it becomes very soft after annealing (heating). It shouldn’t be sold. Plat 900 is perhaps the best alloy. Plat 950 with some other Plat group alloys in the mix (which I have more personal experience with), is extremely white, it polishes well and keeps its polish well because it is hard, it is extremely workable and hardens well with hand wrought techniques, known as ‘work-hardening’. I prefer this metal to all others, but it does soften with heat and may need to be hardened by burnishing (hitting it with a hammer etc), and plannishing (polishing with tungsten bits etc). It also will harden over time and a few days make a lot of difference. It is one of the best metals for hand wrought pieces and fine wires can be polished to extremes and be malleable and hard, offering a lot of scope for a smith wanting fine results. Unfortunately, I know of only one place that sells this alloy.
Ruthenium is the hardest alloy. It takes a lot to polish. I have never seen it produced in Australia and I think it is becoming rare. It takes an eon to polish and is not often cast well as it is prone to porosity. The finish is not as high as most alloys because of poorer casting on a microscopic level, but it will retain a good polish very well. It is greyish in colour. I am not sure if it is ever used in hand wrought pieces, as it is never offered in stock gauge (raw material) and perhaps it is too brittle for that. It must be refined professionally. It is hard but it is only ever cast so it is a bit limited when strength is the priority. Its main weakness is the time it takes to polish. The trade in general don’t achieve the best results due to the extra time needed. It averages approx’ three times as long to polish.
Copper is the most common metal for stock gauge. The vast majority of wedding bands are made from this alloy. It is used for hand wrought pieces. Though cheap to make, it is as good a metal as any for its purpose. The colour is not reddish at all. It takes an excellent polish. It can be fused and it is very malleable. It is not as white as an alloy with more iridium, but is almost every aspect it works as well as the iridium based platinum group metal alloy, which I prefer. It hardens very well by hand forging, perhaps that is in a direct correlation with its malleability. That is, in working the metal, a grain is worked into the structure of the metal. This is true of all precious metals. Many cast metals won’t polish very well.