What makes "glossy brown" copper....glossy?

topstuf

The mint red is rather a fragile looking sorta "powdery" look. Looks very dry and microgranular.
Yet when it is brown, it has a ...."sheen."

What makes that seeming texture change?

Fingering?
The oxide?
What?

mgoodm3

interesting question. Don't know myself.

airplanenut

Since the brown is an oxidized version of the red copper (and will eventually turn green like Lady Liberty), my guess is it simply lies in an altered chemical composition. Possibly think of it like rust--while it's the same metal, the rust is rough and a different color due to oxidation.

Jeremy

topstuf

ttt Anyone else?

???????????

dragon

Sometimes that oily, glossy look on coppers is from the oils from peoples hands from handling the coin, also, some coppers have been purposely oiled at one time for various reasons including to prevent corrosion.

earlwbollinger

wax.
They used to use some kind of s wax on them many many years ago.
I have one like that, that looks glossy chocolate brown, I'd swear someone waxed it with some
kind of a wax.

shylock

Some brown copper retains that fragile looking "powdery" condition you nicely describe, though as Jeremy stated it's less obvious due to the thicker skin it acquires which reflects the light rather than absorbing it. Off-center brown coppers make this more obvious because you can compare the quality of the unstruck planchet vs the struck area. This 1899 off-center strike is full brown yet the powdery texture of the fields is obvious compared to the smooth reflective planchet.

Oiling and other conservation aside, whether a brown copper looks shiney or frosty may have to due with the quality of the planchet and strike when it was minted. This 1895 is an extreme example of a quality planchet that was soft enough to create thick flow lines in the fields when struck. But there are many other high-grade RDs that have smoother fields, varying from lightly frosted to semi-prooflike. I would guess those coins will have a shiney look to them if they ever turn full brown, while that 1895 will retain most of its frosty look no matter how much it turns.

Just a guess based more on observation than knowledge...

BillJones

The term can mean two things to me.

Even when copper tones, it still has the mint luster that is formed in the coin is struck and the medal flows within the dies. It's not as intense as that found on silver, but it is still there.

The second way to look it is the appearance of it after the copper has been given an application of CARE, Blue Ribbon or some other lubricant. CARE and to a lesser extent Blue Ribbon is a decent preservative, and it can enhance the coins for photographing. And the coins do get a cerain gloss to them that many people might find more attractive.

NoGvmnt

WD-40.

Jim

longtimecollector

Maybe they were on Cammies desk when he opened the "duck" picture