How do coins lose luster?

dan1ecu

Hi, Everybody -

I've got a few coins in slabs that are extremely lustrous. Should they stay that way indefinitely? What are some causes of coins losing their luster over time?

Thanks,

Dan

my3cents

wearing off the upper layer of metal, repeatedly dipping the coin which strips away the upper layer of metal, or, the toning (i.e. reaction with the elements) goes through the upper layer of metal.

That's about it.

Just my 3 cents worth

ldhair

Folks trying to make them look better.

tjkillian

To understand what is going on, you need to understand just what luster is. It is the raised part of a coin called "flow lines" that occur when the planchet is squeezed together in the minting process. If you look at a coin very closely with a microscope, you will see tiny ridges around the coin where the light reflect off of to create luster. If these "flow lines" get destroyed, then the coin will loose its luster. Some ways this can happen is through wear or chemical removal (caused by dipping in a mild acid).

Some folks try to recreate luster through whizzing, but that really does not work and just ruins the coin. If unmolested, luster should remain forever.


Tom

Sequitur

Should they stay that way indefinitely?

Very likely yes, the coins will remain lustrous, so long as the slabs are secure.

ibzman350

Tom.....great post, thanx for the lesson.


Question...dipping in a mild acid=acetone bath ??




Herb

Ryana

<< <i>Tom.....great post, thanx for the lesson.


Question...dipping in a mild acid=acetone bath ?? >>



Acetone is a solvent, not an acid. It won't harm the metal although I hear it isn't copper-safe. Something like Jeweluster (now eZest) is a weak sulfuric acid solution. Interestingly, weak sulfuric acid solutions are what the mint used to use to whiten planchets.

Steve27

Over time ALL coins will lose their luster due to oxidation (aka toning); however, if you store your coins properly, they can stay lusterous for decades if not hundreds of years.

nwcs

To reinforce the idea that if a coin is not messed with and is handled well the luster will last forever, I have seen and know of a number of ancient coins with full luster. They are the exception, of course, but amazing!