We were lucky enough to receive some comments from a reader of the blog who has some experience as a copper artist and also happens to be a coin collector. His comments were in response to the recent post about PCGS and Perth Minted Australian Copper. His comments can be found below.
Hi, Regarding the October 09 article on PCGS gradings and rainbow copper coins. While my following comments should not be in any way taken as an accusation I think the reason that PCGS is not inclined to accept such rainbow coins as "genuine" is this "Rainbow Effect" can be brought about with fresh copper by the simple use of a Blow Torch. I know this because I use to do Copper Art at one time as a hobby. There is also a chemical that can be purchased that is sold in Craft Shops that will also give "rainbow" effects to fresh copper. Personally as a Coin Collector and ex copper art artist I am always very wary of any "Rainbow Copper Coins". That is not to say they don't come about this way purely by natural means. However, I can well understand PCGS being nervous to put their name to such coins. Great photography and very intersting article.
Our Response:
Thanks for your input regarding this, we strive to post accurate information from reputable sources. Would you mind if we post your comments (anonymously of course) as a potential cause of this effect? In the USA artificial toning is common practice so I realise it must be difficult. The whole idea of the article is that it is well known by Aussie numismatists that Perth copper does come in spectacular colours and PCGS should be aware of this.
The learned gent was kind enough to reply again:
Like you say there are natural processes where copper will go those rainbow colours by its own accord. However, it is more rare than common as the pennies/half/pennies are not completely copper as you realise they are a form of bronze with two additional metals. It becomes much more difficult for bronze to reach that colour level. The more pure the copper the easier the colour. Annealed will show those colours in areas when heated. If you ever watch a Gas Fitter at work you'll see the copper tubes go multi-colour while using brazing torch etc. Too much heat and the copper will go almost dark/brown/purplish. It is an interesting subject and as I said originally there is no intention on my behalf to say it doesn't happen naturally with Perth Mint Copper Coins. Just suggesting a reason why PCGS might be reluctant to accept same.
So here we have some reasons why PCGS might reject rainbow toned coins, and given the huge premiums rainbow toned US copper coins can garner I can understand this caution. Of course this doesn't apply to most Australian copper, rainbow toned copper are usually later common date coins and of low catalogue value. Also, while Australian rainbow toned coins can command a small premium over their more plain brethren it is never very much, a few tens of dollars at most, and one wonders if it is worth 'doctoring' a coin for such a small benefit.
There's some other things to take into account too. Firstly, rainbow toned Perth copper isn't common, it is much easier to find reddish or brown Perth copper and very nicely rainbow toned coins are quite scarce. Secondly, rainbow toned Melbourne minted copper is almost non existent in comparison to Perth minted material. If someone was out there doctoring coins why are they only doing it to Perth minted material and not those coins minted in Melbourne? The answer of course is that in almost every case the toning is natural and a result of the different ways planchets were prepared in the two mints and the way the coins were struck! For example, why are Perth minted coins so often found with spotting and Melbourne coins not? The Perth mint washed their planchets (before or after striking I am not sure) and the Melbourne mint did not! Secondly, Melbourne minted copper coins of the 1950's and 1960's are, on the whole, much more strongly struck than Perth coins, and it is my experience that the most eye popping rainbow toned coins are also the worst struck coins the Perth mint released!
Now none of this is intended to dis-credit the kind reader of this blog whose comments are found above. After all if you read his responses you'll see that he's not suggesting that rainbow toned Perth copper is artificially toned, but rather why PCGS might think it is artificially toned. My responses to his post have just pointed out to PCGS why rainbow toned Perth copper coins are almost always naturally toned. They are not fiddled with or manipulated like their American brethren can be. Here's hoping someone out there can educate them and we can get these lovely coins protected and graded by a good third party grading company!
Posted by mnemtsas at October 8, 2009 8:12 AM
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