Why might a doctored coin turn colors over time?

MrEureka

I'm wondering if the answer might provide clues as to safeguards that could be taken and processes that could be performed before grading the coins.

ricko

Most of the time, I believe it would change colors due to residues (improperly or incompletely removed) from the 'medical' procedure. I would believe that the more competent 'physicians' would be able to avoid this. That statement applies mostly to enhanced color. Now, puttying, tooling or adding/removing metal will produce different effects. Metal movement will expose new and/or stressed metal, which affects molecular structure (the stressing) allowing for the environment to act upon the area affected. Puttying, of course, depending on the material, has a 'chemical life' and will change over extended periods of time. Cheers, RickO

dizzyfoxx

For every chemically induced action, there will be an eventual reaction.

BaseballAbs

Let me take a guess, because the chemical used is still active and was not properly removed or neutralized and there for still active.

sinin1

you need more to your question as it has many answers

putty on gold?
artifical frost on proofs?
dipped coin?
plugged hole?
light whizz?
art toning?
copper?

TwoSides2aCoin

We need the chemist, metallurgist and a few other analytical experts here.

LindeDad

Time in the environment is going to affect coins just in and of its self.
So until we can hermetically seal a coin in an inert environment they are going to change color.

291fifth

The PhD chemists that have been hired by some "doctors" could answer the question.

GoldenEyeNumismatics

Probably for reasons not far from why undoctored coins can change color over time.

MrEureka

For a more specific question, why would the putty on a coin become more obvious over time? I believe it's the putty that changes color, not the coin. What is going on here, and why?

keets

i know that a "thumbed" coin will sometimes turn a different color in that area than in the area around it.

GoldenEyeNumismatics

<< <i>For a more specific question, why would the putty on a coin become more obvious over time? I believe it's the putty that changes color, not the coin. What is going on here, and why? >>



The applied material probably begins to lift slightly off the surface, creating a veneer of air to diffuse the light. This would turn the translucent "putty" into an opaque layer.

BAJJERFAN

<< <i>For a more specific question, why would the putty on a coin become more obvious over time? I believe it's the putty that changes color, not the coin. What is going on here, and why? >>



Does the putty actually shrink as it cures over time. If it is like window putty, the oils such as linseed used in its manufacture contain unsaturated sites which react with oxygen in the air.

BAJJERFAN

<< <i>The PhD chemists that have been hired by some "doctors" could answer the question. >>



Cuz it's doctoRED.

I'd ventured to guess that the chemical reaction that produces the toning continues on for some time after it is "terminated" by whatever means.

yellowkid

<< <i>For every chemically induced action, there will be an eventual reaction. >>



I like that, you could be the Newton of numismatics if it catches on.

ProofCents

The surface of the coin is not longer stable

Shamika

Residue. Pure and simple.

If the coin has been completely (and I mean 100%) cleaned of chemical residue, it should be stable. Or at least as stable as the base metal is.

BAJJERFAN

<< <i>The surface of the coin is not longer stable >>



It is shorter stable?

sinin1

putty probably changes color over time related to moisture content

I would take a guess that after years, the plasticity(and moisture?) that was present on use, slowly evaporates,
reducing the size and causing cracking/deformation -> color change


have you heard of putty on anything other than gold?


have some used it to make DCAMs, or is that something that is painted on?