Do you know that 6000 medals for the 2008 Olympics Games were made by Shanghai Mint and they are blend with jade?
The Coin Link has a story.
:-)Inlaying jade
The Shanghai Mint, under the China Banknote Printing and Minting Corp, works mainly in casting metal coins for circulation, and precious metal badges. It is the provider not only of the medals for the Olympic Games and Paralympics, but also of the medals for demonstration events, and commemoration badges.
For the first time in Olympic history, the medals for the Beijing Games blend metal and jade. The technology of inlaying jade into metal can be dated back to the Han Dynasty almost 2000 years ago.
Blending metal and jade is a new technique in minting coins. It is not easy to bond jade perfectly with metal. The key to the process lies in the inner layer of the medal metal and the groove of the jade ring. A seal ring is put between the inner layer and the groove to join the metal and jade together. The seal can also buffer the effect of vibration to protect the jade against impact.
Working with jade
The Jade ring must be matched with the medal metal, so it must comply with the necessary outer and inner diameters. Jade rings used for casting Olympic medals have been subject to rigorous quality controls, and those not up to the standard have been discarded.
To make use of those jade rings that do meet the quality criteria, metal medals were produced to fit the jade rings, and more than ten different sizes of seal ring were designed.
To avoid any loosening of the jade rings due to aging of the seals, glue has been used in casting the Olympic medals, a painstaking manual process.
Experts from the International Olympic Committee (IOC) were concerned about the risk of fragility when the jade ring design was proposed. The IOC required that jade rings should be strong enough to withstand a 2-meter drop test. The Shanghai Mint raised that standard to three meters.
A considerable effort has been made to bond the Jade rings successfully to the medals. Medals can survive a 3-meter drop test with only minor cracks on the jade rings, proved through destructive experiments.
The unique feature of the medals for the Beijing Olympics – the inlaying with jade – is commonly regarded as the most difficult process in making the medals. But Liang Dekui, chief of the production division of the Shanghai Mint, does not share this view, “There are 30 steps in making the gold medal, and the jade inlay is only one of these. The major challenge is in the processing of the metal because we are not familiar with two thirds of the process.”
Medal production differs greatly from the traditional production of coins. Since production of a limited series is a far cry from mass production, the Shanghai Mint encountered a range of practical difficulties in producing the Olympic medals.
According to Liang, the biggest single problem was welding the medals to their clasps at high temperature without producing any change in the color of the metal.
The names of the individual sports were engraved on the medals after pressing. The following process involved spraying lacquer over the medals to protect their surface. But the lacquer had to be evenly sprayed without changing the color and luster of the medal’s surface.
Because the jade rings did not arrive in Shanghai on schedule, much of the jade inlay work had to be carried out in June, the rainy season in Shanghai. Indoor humidity reached 80-90 percent. Moisture and sulfur in the air might easily have altered the surface color of the silver and bronze medals.
In response, the Shanghai Mint urgently equipped four powerful moisture reducing machines to lower the humidity level. In addition, all workers were required to wear face masks to prevent breath and saliva from harming the medals. “The medals represent a lifetime’s achievement for the competitors. It would be disappointing if the colors were to change with the passage of time. So we took great care.”
Olympic medal production is subject to zero defect. In order to meet the standard, the gold plating had to be strictly controlled. “The gold medal is not of pure gold. It is made of pure silver, plated with no less than six grams of gold. Any medals with less than six grams of gold plating were rejected.”
In order to ensure the exact weight of the plated gold, the workers had to control the duration of the electroplating and the strength of the electric current. Additionally, uneven color distribution over the medal surface was not acceptable.
Each medal was weighed before being put into the electroplating bath. To better control time and achieve the right finish, medals for electroplating were batched together according to weight. Eventually each medal was plated with 6 to 6.1 grams of gold.
In order to improve the look of the medals, the top end of the ribbon clasp was designed with a point. During bulk production processes after the clasps had been welded, there was a risk of medals scraping against each other. To avoid medals getting scratched, the staff at the Mint designed a number of protective measures such as the “safety bag” – each medal was stored in a soft paper bag.
All the staff at the Mint treated the Olympic medal making task with the utmost seriousness. They had not only to guarantee the quality of medal production within their time deadlines, but also to ensure the security of the medals. Strict quality control measures were implemented to guarantee the safety of the materials and the quality of the final product. Employees also signed a non-disclosure agreement forbidding them from talking to their families about the making of the medals.
