Featured My Experiment using MS70 Coin Brightener.

A very useful post.
As the Chinese say, "One picture is worth a thousand words".

 

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I have seen some blue/purple color on copper that I thought looked like NT. I suspect this develops over an extended period of time from prolonged exposure to some unknown substance in the coin's local environment. Obviously, however, the most common type of oxidation we see on copper alloy coins is the brown to black copper oxide.

This is an informative article on copper reactivity.
https://copperalliance.org.uk/knowl...ation-resources/copper-reactivity-patination/

I have wondered if the "unnatural" blue/purple seen from things like MS70 isn't more related to the particular alloy of the coin. It seems that the areas that take on the most color are the areas that were a darker brown to start. If the degree of copper oxide formation in these areas is more pronounced, and the MS70 somehow washes away the oxidized copper, would not the remaining tin and zinc in the alloy be more visible giving a blue/purple color as light is refracted from the coin?

Although the ratios of Cu, Sn, and Zn in small cents has remained fairly constant (with some notable changes), surely there have been major differences in the billions of alloyed planchets manufactured over the years. This could certainly account for the unpredictable results people describe when copper alloy coins are exposed to any chemical that alters its oxidized surface.

JMO

 

BOIL IN SALINE SOLUTION. VERY BAD

 

I have discussed this topic and have yet to confirm this but I have on several occasions toned copper with MS70 and removed the tone with a subsequent bath of MS70 followed immediatly!! by an acetone dunk. Try it.

 

This coin was soaked in MS70 and then rinsed with distilled water. The coin has remained stable 20 years now and was slabbed by ANACS maybe 18 or 20 years ago. My experience with the product on UNC and Proof copper has been negative though overall. Pink unnatural hues as well as Blue and darker coins that are not as stable long term. I was doing a lot of early proofs and experimented on some copper and found out fast to avoid this product. My own perspective and experience only. Silver the product rocks with careful diluted use.