Precious Medals

Article From: Products Finishing, from Technic Inc.

Posted on: 3/1/2010

Making the medals for the 2010 Winter Olympic Games
 February 2010 marked the return of the Winter Olympics to North America.

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 February 2010 marked the return of the Winter Olympics to North America. Vancouver and Whistler, BC hosted the XXI Olympic Winter Games from February 12-28. This month, the same venues are in use for the 2010 Paralympic Winter Games, which run from March 12-21.

Vancouver, along with the Coast Mountain region of British Columbia, is one of the world's leading winter sports destinations. Whistler is consistently ranked as the top mountain resort in North America. Both sites have provided and will provide the venue for this year's showcase of sportsmanship and athletic accomplishment.

 

Unique Medals

Of course, No Olympics would be complete without the gold, silver and bronze medals that are awarded to top finishers in each event. Designs for medals to be presented at the Vancouver Winter Olympics were unveiled on October 15. Medals feature original West Coast aboriginal designs of an orca and a raven.

In an Olympic first, each medal will be unique, featuring part of an image cropped from two large master artworks by Corrine Hunt, a Canadian designer and artist. Also for the first time, the medals are not flat. Instead, they have an undulating surface intended to represent the West Coast landscape of mountains, waves and drifting snow. Weighing in at 500-576 g each, the medals are also among the heaviest in Olympic Games history.

Medals awarded at the Paralympics will feature parts of a larger West Coast aboriginal image of the raven, imprinted on squared-circles of undulating metal. Canadian industrial designer and architect Omer Arbel, also of Vancouver, created the undulating design of the medals, which were struck nine times each to achieve the distinctive look as part of a 30-step medal fabrication process.

For months proceeding the medals' unveiling, metal supplier Teck Cominco Ltd., the Vancouver Organizing Committee and the Royal Canadian Mint planned production. Teck supplied the metals used in production of more than 1,000 medals to be awarded at the games, including 2.05 kg of gold, 1,950 kg of silver (all Olympic gold and silver medals contain mainly sterling silver) and 903 kg of copper sourced from its operations around the world. In another first, the medals will contain metals recovered from processing of circuit boards from end-of-life electronics otherwise destined for the landfill.

The medal production process took more than a year, and began with CNC milling of 12 undulated dies for striking medals into their unconventional shape. Blanks for the medals themselves cut to precise width and thickness from cast and rolled bar stock. Blanks were then triple struck three separate times, with polishing and annealing between each group of strikes to gradually form the medal into its complex final shape.

Next, Mint employees pressed a unique Mint-designed ribbon hanger into the body of each medal. Hangers were tested to withstand 200 lb of pressure. Designers converted the 1,014 unique medal designs from two original artworks using software to prepare laser etching of the designs and text onto each medal's uneven surface.

Some medals were then finished using a transparent protective coating to prevent premature wear and tarnishing before cold-weather testing to a temperature of -20°C to confirm their integrity and durability.

 

Going for the Gold

Gold medals, obviously, required deposition of a layer of gold over the sterling silver substrate. This process began when Teck chemically refined gold doré bars (~87.5% pure) into gold grains of 99.99% purity. The grains were then used in an electroplating process supplied by Technic Inc. (Cranston, RI) and operated by the Royal Canadian Mint.

Technical service reps from Technic Canada began by reviewing the cosmetic and performance requirements for the gold plating with the Mint's engineering staff. They developed the following sequence for gold electroplating of the medals.

Pretreatment included degreasing followed by an alkaline electroclean step to further break down and remove oils and debris. Medals were then subjected to an acid activator designed to neutralize any remaining alkalinity and assure that all oxides or tarnish were removed from the surface.

Gold plating was a two-step process, with a gold strike and separate gold plate typically used. The strike plating, because of low metal and low efficiency, is formulated to provide good adhesion for the initial few micro-inches of deposit. The strike also helps collect contamination from various pretreatment steps, trapping it there to prevent contamination of the primary gold plating solution.

The primary plating solution has a higher concentration of gold with a much higher efficiency. This is the step where the medals are plated to final thickness and color specifications.

Medals were individually rack plated, with emphasis placed on deposit color, even thickness distribution, durability and the correct hardness to accept laser engraving of the athlete's name and Olympic results. This step gives the Olympic gold medal its lustrous color and brightness.

The Olympic medals were plated to a heavy thickness of 20 µm of gold using a process with a cathode efficiency of about 30%. This efficiency obviously results in slower plating, but thickness distribution is improved. The effective plating time needed to achieve 20 µm of thickness at current density of 1.0 A/dm2 was about 100 min.

After gold plating, medals were rinsed with deionized water and then subjected to a proprietary protective clear coating process. Clear coat application was followed by rinsing and drying.


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