Have you noticed how many gold engagement rings have platinum settings? This is because platinum’s high density, strength, and resistance to metal erosion makes it the most ideal metal for securing valuable gems—provided, of course, the right platinum alloy is used. The way the metal is worked during jewellery manufacturing also plays an important role in the durability of the platinum.
Platinum alloys
Platinum Iridium (PLATIR)
Platinum Iridium – consisting of 95% platinum with 5% iridium – was once the most widely used platinum alloy. It increases the Vickers hardness of pure platinum which is still too soft for sturdy jewellery and casting. However, PLATIR has a high work hardenability, which can further increase platinum’s Vickers hardness
Many Edwardian and Art Deco pieces were made with PLATIR, as the alloy’s malleability makes it ideal for the fabrication of intricate filigree and milgrain metal work. Given early platinum pieces were hand-worked instead of cast, their hardness was suitable for jewellery wear.
It was only in the mid-1950s that modern-day centrifugal vacuum casting was developed; however, this was not commercially implemented to a larger extent until the 1970s. According to Platinum Guild International (PGI), PLATIR should not be used in casting because it is too soft and may likely result in bent prongs, misshapen shanks, and overall poor wear performance.
Platinum Cobalt (PLATCO)
Platinum Cobalt – consisting of 95% platinum with 5% cobalt – is a good flowing alloy recommended for casting. It can be hardened with cold hammering. Cobalt platinum alloys are slightly magnetic, which is regarded as undesirable for a precious metal. In fact, there have been some cases where jewellery professionals have misidentified PLATCO as a non-precious metal because it was slightly attracted to a magnet.
Platinum Ruthenium (PLATRU)
Platinum Ruthenium – consisting of 95% platinum with 5% ruthenium – is a hard, ductile general purpose alloy which is ideal for everyday rings. When it is cold-hammered or die-struck, its hardness increases. Luxury companies (including Harry Winston, Tiffany & Co., Cartier, Bulgari, and so forth) use PLATRU to ensure a metal that is “the whitest white,” which brings out the best in high-quality diamonds.
Dangers of choosing the wrong alloy
If an unsuitable alloy is used for jewellery, a piece’s prongs and mountings may bend and result in the loss of stones.
It is especially important for eternity bands to be made with an alloy of sufficient hardness such as PLATRU. If the wrong alloy is used, the stones could fall out when the ring is deformed, which could occur by simply grabbing a suitcase by its handle.
Benefits of platinum
In jewellery, platinum offers several advantages. Namely, the metal’s natural white hue enhances the lack of colour in D- to F-colour diamonds. By comparison, since white gold is created with yellow gold, the metal may be yellowish, so it is often plated with rhodium to resemble platinum. Over time, this plating can wear off, requiring the jewellery to be re-plated. The rhodium plating also complicates repair work and resizing, as this layer will burn in the heat of a soldering torch, flaking off the jewellery piece and making it impossible for the solder to flow. Meanwhile, platinum does not need to be plated.
In addition to its colouring, the metal offers several other benefits:
- Platinum does not tarnish and is not attacked by chemicals. While the same can be said about pure gold, the metals used to make gold alloys can sometimes cause it to discolour and be corroded by, for example, chlorine in swimming pools and household cleaning solutions.
- Platinum is hypoallergenic (unlike nickel white gold, which can cause a reaction in some wearers).
- Because of its higher density, platinum is stronger than white gold and retains its shape if the right alloy and manufacturing process is used. As such, it is more suitable for delicate mountings and thin prongs. Platinum prongs stay in place when formed and do not spring back like white gold prongs.
- Platinum’s high malleability makes it a much better shock absorber than white gold, which can dampen the impact of a hard knock and potentially save a gemstone from chipping.
- Platinum pieces can come at an affordable price, while also offering the look of expensive high-end diamond jewellery.
- Platinum jewellery lasts longer and resists abrasion better than gold. When gold is scratched or polished, part of the metal is worn away, whereas platinum is displaced or compressed. Considering platinum does not wear thin, it is, therefore, the precious metal of choice to create heirloom pieces that can get handed down from generation to generation.
Strength in design
Today, there are more platinum alloy options available than 20 years ago, and many of these are specifically engineered to fulfil certain manufacturing and lifecycle requirements. When selecting an alloy, it is important to choose one able to withstand the wear and tear a piece will be subjected to. The structural design, durability, and strength of any jewellery design is ultimately the responsibility of the creator, and only well-designed pieces with the appropriate metals will stand the test of time.
At Cape Precious Metals we offer various brilliant Platinum alloy metals with Platinum Ruthenium (PLATRU) being our most popular. We sell this in granule and bar form.
To complement this we also offer Platinum Butterflies and Platinum Solders.
