What causes this blue cameo toning on copper proofs??

Ed62 · January 8, 2013 8:58AM

airplanenut · January 8, 2013 9:10AM

If you're asking why the frost looks blue, it's because the entire coin is toned in blue. At that lighting angle, only the toning on the frosty devices gets picked up, so the rest of the coin looks brown. If the coin were well illuminated, you'd see the whole thing glowing blue.

SUMORADA · January 8, 2013 9:41AM

nevermind.........pretty coin!

coinsarefun · January 8, 2013 9:56AM

As in copper and silver
I have always wondered that too.
I came to a conclusion after seeing so manny
proofs toned red and blue or mostly blue.

I'm not sure if its the right conclusion but here goes

Most of the older coins and proof coins were stored
in coin cabinets where there was felt shelving and over
those years of being there have tones from the felt.

Simaliar to the ASE proofs. If they take them out of the capsules
and place them in the mint pakaging they take on a blue or
blue/ red toning. Sometimes purple even.

If its not right will someone explain then?

coinsarefun · January 8, 2013 10:30AM

Or it can be something else as this is graded red/brown

Prooflike, copper token.

keets · January 8, 2013 11:20AM

J-935.

If you're asking why the frost looks blue
what about when the fields look blue??

If its not right will someone explain then?
I don't claim to be an expert in tone, but the color isn't affected by the color of the contaminant that causes it, it's the result of light reflected/refracted back and the thickness of the surface film.

L1ncolnF4n · January 9, 2013 3:31AM

MS-70 and Ammonia are two chemicals which can cause copper to blue depending on how they're used (sometimes it's nice, other times not so much).

JCMhouston · January 9, 2013 5:25AM

I've seen some early copper that looked like that after a bath in MS70.

johnny9434 · January 9, 2013 5:25AM

i wanna say blue dykem for steel but that wouldnt be right

Coinsponge · January 9, 2013 6:17AM

<< <i>

>>

Not an expert but I think the blue toning on a cameo would be caused by the oxidation of copper into cupric oxide and it probably affects the cameo more because it has more exposure to oxygen due to the "rough" texture. A low porosity proof field would be very resistant to oxygen reactions. Just my guess.

keets · January 9, 2013 6:58AM

A low porosity proof field would be very resistant to oxygen reactions.

the Pattern I have pictured would seem to violate your premise since the smooth fields toned blue and the rough devices tended to stay red/brown. I don't think there's any real mystery here, it's just that as Copper darkens it does tend to have bluish color when the light is at the proper angle relative to the viewer/camera lens. Copper tone is a different animal than Silver tone; Copper almost always has to be at the proper angle to see the color while Silver color can be seen most of the time yet still has that sweet spot of optimal reflection.

Coinsponge · January 9, 2013 7:36AM

Missed that earlier. You are probably right. The angle of viewing/lighting makes it look that way. Nice pattern.

What causes this blue cameo toning on copper proofs??

Comments

Leave a Comment