Asteria Colored Diamonds

Asteria Colored Diamonds


TechForm Platinum Jewelry Casting

Leibish & Co

Friday, March 4, 2016

How Do I Choose The Best Precious Metal Alloy For My Jewelry?

This is the first in a monthly series of educational articles for jewelry professionals and consumers by Teresa Frye, founder of TechForm Advanced Casting  

The precious metal alloy you choose for your jewelry can make a world of difference for both the manufacture of your designs and consumers. Therefore, understanding the risks and benefits associated with alloy choices can go far towards assuring that you get the look you want and the quality you need. Every jeweler benefits from a deeper understanding of an alloy’s characteristics. Listed below are the most important of these characteristics.

While this one may seem obvious, there is a lot of nuance in the world of color that can make a big difference in the end product. For example, matching a 950 platinum cobalt wedding band with a 950 platinum ruthenium engagement ring will yield a noticeably different color between the two. And while this might not be obvious when the ring is new and highly polished, with time and wear it will become more apparent. White gold runs the same risk. When gold alloys are whitened with palladium versus nickel, the latter will be much whiter than the former. Therefore, it is a good idea to do your homework and find suitable color matches, whether you are trying to match a customer’s existing piece of jewelry or launch a new line.

Tarnish Resistance
Although most jewelers are fairly well-versed in tarnish resistance, most consumers are not. A full understanding and disclosure of tarnish resistance for the products you sell will go far to protect your reputation. White gold tarnishing is probably the least understood by the consumer, so extra care should be taken at the point of sale to assure they understand that the metal will change color over time or that rhodium plating has been used and will eventually start to wear off. Your metal supplier should know how their alloys perform and can help you with the information you need to inform your customers.

Molten Fluidity
When you design it is important to understand the molten fluidity of your chosen alloys. While silver and yellow gold alloys have high fluidity that enable good flow into fine cross-sections, platinum and some of the white gold alloys do not. Fluidity is determined by a number of factors including an alloy’s solidification range. Alloys with inherently low fluidity, such as platinum ruthenium, need larger sprues and generally larger cross-sections to adequately fill all features of the design. If you are unsure of an alloy’s fluidity, your caster or the technical contact at your alloy supplier should be able to help.

Mechanical Properties
The mechanical properties for an alloy, including strength, ductility and hardness measurements, are crucial to understanding how your jewelry will wear for the consumer. In addition, they also indicate how an alloy will behave on the bench in terms of finishing and setting. The most common mechanical property cited in the jewelry industry is hardness, although this is only one measure and not necessarily the most important one for jewelry manufacturing. It is equally important to know how strong an alloy is to assure it will not distort with normal wear, or how ductile it is, which will indicate the degree of ease in setting. For example, while 950 platinum iridium is a dream to cast, polish and set, it has very low strength and hardness. If you understand the mechanical properties of this alloy, you will immediately conclude that the consumer cannot be well-served because your design will easily distort and potentially lose stones. Simply switching to a stronger alloy will shift these properties higher and protect your design from unnecessary failures. Your alloy supplier should be able to give you mechanical properties for your alloys if you do not already have them. 

8mm platinum Lattice ring with pave-set white diamonds by Etienne Perret

Hypo-allergenic Properties
Lastly, it is important to know whether your alloy contains nickel. A small but significant portion of the population has nickel sensitivity. Typically, these individuals already had some reaction to a jewelry metal in the past, and they will be looking to you to assure they get the right metal to avoid reactions in the future. Ask your metal supplier for a breakdown of the elements in their gold alloys, and avoid any that contain nickel. Another option is to use a platinum alloy composed of only platinum group metals, such as 950 platinum ruthenium or 900 platinum iridium. These alloys have no known instances of allergic reactions and are safest for those who are highly sensitive to base metals.

Teresa Frye is founder of TechForm, which specializes in the casting of platinum group metals for the jewelry, medical, and aerospace industries. She is also founder of the Portland Jewelry Symposium, an annual gathering of custom jewelers, designers, and retailers described as a “great think tank” for jewelers who are passionate about their craft. Frye is a renowned specialist on the casting of platinum group metals who speaks at jewelry events throughout the world. 

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