Removing Toning From Proof Coins

Actually MS70 is just a catchy name. AFAIK, it is mostly potassium hydroxide.

 

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And some sulfonates.

 

What GDJMSP said.

 

No, the rule is: do not IMPROPERLY clean coins.

 

There you go. Now watch all the blue cents showing up. Why? 'Cause some people can't help themselves - they're all about unnatural colors on their coins.

 

halfcent1793, posed: "The blue color on the acetone-treated coins is the natural color of the toning. It got that way because you removed the oil on the surface. You can make it brown again by adding some oil, and you can turn it back by removing the oil. Adding and removing the oil have no effect on the coin itself, just the appearance of it. Unless, of course, you hairline the coin by brushing it."

IMHO, most of the above post is true. Since the color on a coin can be from oxidation or some substance applied to its surface. This substance can either have a color of its own or react chemically to the surface of the coin to change its color.

As to the rest ...please explain:

The poster claims the blue color is natural toning. Yet, by putting oil back on the coin, the natural toning is removed and it turns BROWN! Then, if we remove the TRANSPARENT oils on the coins BROWN surface, its natural BLUE color that was "hiding" under the clear and transparent surface oils returns.

Please... If copper collectors/dealers like chemically or environmentally altered and very attractive "blue" copper that's fine. But much of it can be produced on a coin in less than a minute and AFAIK most of the time there is no difference in the color.

 

Yup. There is nothing "natural" about blue copper.

 

"Transparent" isn't that simple. We've all seen the colorful sheen of oil or gasoline on a water surface, and both liquids are (approximately) transparent.

For that matter, it's a cloudy day outside; since water is transparent, how can I see the clouds?

Patterns and textures at a fine scale absolutely can cause a surface to change color when it's wet vs. when it's dry. I've seen numerous seashells that show vibrant color when they're wet (with water), but are very dull when they're dry. Toned cents? I have no data. I'm feeling some temptation to experiment, though...

 

Thanks for adding to the discussion; however, this discussion is not about the correct definition of "transparent."

There is a difference between an oil slick and clear lacquer. If a piece of metal has a CLEAR, uncolored, transparent coating it will not cover its true color - in this case blue. For example, I'll bet a blue proof Indian cent will stay blue when sprayed with clear lacquer. If I had one I'd do it and provide images.

Nevertheless, the blue color on copper can be produced in seconds by a coin doctor or conservator (in this case not on purpose as I've done it ) or naturally over several years.

 

Kurt Bellman, posted: "Yup. There is nothing "natural" about blue copper."

Actually, This is not the case. Both silver & copper can change to blue over a period of time under the right conditions. many of these coins came out of famous collections. No one "altered" them.

 

Yeah, yeah, I 've got a few cents with lots of blue on them. Funny thing is - that blue WAS NOT THERE when they went into ANACS plastic, and now it is there. For over forty years they "lived" outside plastic, 10 of them in MY possession, and not a TRACE of blue. Three years in an ANACS (small slab) slab, and presto, BLUE! "Chemically inert materials" my backside!

And don't get me started on what ANACS slabs did to proof nickels. Even with more recent experiences with PCGS and NGC, all that I see convinces me that slabs CAUSE toning.

That'd be okay if I LIKED toning, but I don't. Lately I put ALL my slabbed coins in boxes with anti-toning junk in there with them. That's why I jump down people's throats when they post that slabs are "air tight". What they ought to have is tiny exhaust fans to rid the slab of the inherent contaminents!

 

Do an experiment, dip a cent in vinegar and let it sit and dry. What color does it turn to?

 

Plastics "out-gas" if that is the correct term. Try to combine that with a little "warmth."

 

I wonder if I should start up a business selling vacuum safes for coin storage...

 

Ja, Ausgasung.

 

Try placing this in your boxes, next to the desiccant.

 

How long do you have to wait?

 

Give it a couple of days.