Primer on Nordic Gold

JohnZ

I was wondering about this alloy myself, so I found some info on it. Originally developed in Sweden, it is now used in the Euro coins, as well as by several other countries.

Mariann Sundberg, now director of the Scandinavian Copper Development Association was actively involved in the development of the copper alloy, 'Nordic Gold' used in the new Euro 10, 20, 50 cent coins introduced in January 2002. The following questions were presented to her in conjunction with the introduction of the Euro.


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1. Nordic gold is the new alloy for the 10, 20 and 50 Euro Cent coins. What is Nordic gold and was it especially created for the Euro?
Nordic Gold is an alloy which combines copper (89%), with smaller quantities of aluminium, zinc and tin. It was originally developed more than 10 years ago for the Swedish Mint and is today being used for the Swedish 10 Crown coin.

2. Did the Swedish Mint have specific expectations for this alloy?

When the Swedish Mint was looking for a new material for the 10 Crown coin, they identified a number of performance criteria that had to be met by any material submitted for approval. The mint specifically wanted the following:

The appearance of the coin had to be golden and tarnish resistant. No discoloration of the golden colour should occur over time.
The material had to be malleable (formable) to make the minting process easy.
The material had to be durable and resistant to long usage and heavy handling.
And, equally important, the Mint was very concerned about possible allergic reactions caused by some metals, so the new metal had to be non-allergenic.
The final Nordic Gold alloy was able to meet all these requirements and has now been used in the Swedish 10 Crown coin for over 10 years.

3. What were some of your major challenges along the way?

One of the major challenges was the colour of the metal. Copper is the only metal, besides gold, with a colour that differs from grey. By alloying the red-brown copper, the colour of something like a coin can be changed considerably to obtain a look much closer to gold, hence it's name, Nordic Gold. The second key challenge was to ensure the tarnish resistance of the coins. We tested the material for its reaction to, amongst others, hand sweat, leather, and various clothing fabrics. We tried a number of combinations, and as it turned out, the most tarnish resistant combination was copper alloyed with aluminium, zinc and tin.

4. Why was the Swedish Mint concerned about allergic reactions?

The Swedish Mint was concerned because research has shown that other traditional metals used in coins can present certain people with contact allergy reactions. This made our combinations very tricky to ensure that we combined copper with metals minimised this possibility. Nordic Gold was ideal in that it induced little to no allergic reaction. A parallel health concern to be addressed was that of hygiene. The daily handling of coins can provide an easy way for bacteria to spread quickly from one individual to another. Copper has the unique characteristic of being a naturally antibacterial material. This hygienic aspect of copper is very well known and explains many of copper's other uses, such as doorknobs and handles in antiseptic environments like hospitals.

5. Can you tell us a little more about the security features of the coins?

The security features are perhaps the most complex, because this new currency has been introduced simultaneously across such a wide area. Obviously, when we originally worked on Nordic Gold for the Swedish Mint, we had these concerns as well, so a lot of these issues were already addressed.

Obviously there are some parts of the process that we won't reveal, but there are some very practical features in developing a coin for use as currency. For example, vending machines across Europe must have a way of identifying coins, including those minted and issued by other countries, as real. This requires every coin denomination to have a unique "electronic signature".

In addition, the electrical conductivity of the coins is important to identify coins. Again, this is where copper is a great choice. It's excellent conductivity can be changed over a large range of values by different alloy additions. Nordic Gold possesses just the right levels of conductivity to meet security standards.

6. When you say that the alloy needs to be malleable and durable at the same time, isn't that a contradiction?

Not really a contradiction, it just sounds that way. Copper's malleability enables the mint to use a much more efficient process in striking the coins. The copper alloys are cast into cakes or thick strips and then rolled into the correct coin thickness. The coin blanks are stamped from the finished strip and then rimmed and struck. One of the best things about copper is that it is malleable to allow fairly complex reliefs, as you can see on the new Euro coins. During embossing, the coins are further hardened, with copper's resistance to corrosion then ensuring a long life.

7. How important was copper's recyclability in the selection process?

Copper is fully recyclable, which in this time of increasing environmental consciousness, made it even more of a perfect choice for the currency. It is well known that the remelting and reuse of copper has been practiced since the Bronze Age. It is estimated that more than 80% of all the copper ever mined is still in use today and the value of scrap material, at the end of its useful life, will guarantee copper's future recycling. Maybe that's another reason why I found it so interesting to use - imagine the long line of coins from the Roman Empire, the Vikings, the French.

© The UK Copper Development Assoc. Used with their kind permission. www.cda.org.uk

trozau

good reading. thanks.

newbiecollector

Thanks...... It helps me to understand some terms.

JohnZ

What interested me was the fact that vending machines are measuring the conductivity of the metal to determine it's authenticity. This is the first I've ever heard of such a thing, but it makes perfect sense.

Askari

The "allergy" thing was an overblown concern about the supposed allergic properties of nickel. Nordic Gold, though, does seem to retain its color very well over time with handling. It was seriously considered for the Sac "golden" dollar, but domestic metal suppliers really pushed Congress about the "sacrilege" of buying coinage metal from a foreign country. The mint's own efforts at achieving the same objectives is readily apparent.

1jester

Quite informative!