What foreign substance is placed on proof coins which later results in an unnatural blue haze?

Longacre

I was taking a look at a catalog, and on at least two proof coins, the cataloger stated something along the lines of "a closer examination of this proof coin is suggested as there is a blue haze in the fields", and "at first glance the grade is much higher, but an unnatural blue haze is present in the fields".

What foreign substance is placed on proof coins to make them grade higher, which ultimately turns the fields blue? Is it a particular chemical or other substance? Is there a doctor in the house who can answer this question?

OPA

Copper?

manymortages

silverware polish maybe

Animalkeeper

I have always been told by those with more experience than I that the blue haze on proof coins was from too much contact with the cellophane holders used by the mint. I own a few coins with it.

I was even told by one dealer that it did not significantly reduce the value but I personally don't find it attractive......

COINB0Y

PVC

BAJJERFAN

Selsun Blue??

Paleodale

I Have always had a theory that it is manufacturing oil residue and or a combination of the oils and the rinse... I have dipped new clad and silver kennedy's in acetone and put them back in the original case and the Haze has never appeared... I have washed the haze off of coins that were 30 years old in acetone and the haze has never reappeared... if you mix oil and humidity {water} the oil will get a milky white color to it.. I still believe it is from the mints manufacturing oils.. What else could cause this,???? it even happens to newer modern coins that are only five years old or less... They have used the same cases as in other years past,, but for some reason some years are more prone to it,, so I don't think its in the packaging... it has to be some sort of residue that is left on the coin after the minting process....

IrishMike

I don't think you can blame the mint cellos for the blue haze as many of the brown Ikes have blue haze.