What specifically causes orange peel surfaces on proof gold?

Longacre

I was taking a look at the upcoming Stack's auction, and this coin caught my eye. Does anyone know specifically what causes the orange peel surfaces on proof gold? I like the look, but was curious how the surfaces get that way. Here is the description in the catalog, as well as the picture:

1899 Proof-63 CAM (PCGS).

A splendid example at the Proof-63 level of this late 19th-century issue, with the desirable "orange peel" character to the mirror surfaces on both obverse and reverse. Excellent eye appeal. Original "warm" color, not brightened or enhanced (such original pieces are becoming increasingly hard to find in today's market).

PCGS Population 1; 2 finer (Proof-66 Cameo finest).

Regulated

The truth is that no one really knows what causes it (although a lot of people will claim they know). Due to the wave-like nature of orangepeel, I have begun to suspect that it is a function of multiple strikes from a fresh, uneroded die. Perhaps we should commission a study with Ron Landis.

guitarwes

It also looks like Ms. Liberty sneezed.

Regulated

It seems like there was an interesting thread about this a year or so ago.

Longacre

<< <i>It seems like there was an interesting thread about this a year or so ago. >>




I see that now. Thanks.

And I will overlook the fact that michael called someone "his tasty bananna split"!

Zoins

Link?

EagleEye

Claiming to know, but I wasn't there.

It is found on extremely early die state pieces, not just gold. It is due to the shrinkage of the dies during the hardening process. The deep deep mirrors are due to the dies being polished while in the soft state.

Regulated

Rick -

Have you ever encountered any PL business strike pieces with orange peel? It seems odd to me that the effect is only encountered on proofs.

D

EagleEye

Well I know extremely early die state Lincolns look like Matte proofs, but that is different. I think the polished fields really bring out the subtle crystallization that the die face goes through. BTW, to harden the dies, I believe they heated them in charcoal to eliminate scaling due to oxygen then quickly quenched it in water.

Regulated

I really want to set up my own mini-mint, so I can actually get hands-on experience doing this stuff.

EagleEye

BTW, I love the orange-peel on Proof Indians. Most Cameos are found with the orange-peel.

Also I think the gold that has orange-peel is prettry sure not to have been altered by a laser or metal manipulation. Another good reason to like it.

MrEureka

You never see orange peel on silver or nickel coins, only on copper and gold. Any guesses why?

Coinosaurus

<< <i>You never see orange peel on silver or nickel coins, only on copper and gold. Any guesses why? >>



Maybe because it is softer?

ONETHREE

Orange Peel? What Orange Peel?

GoldenEyeNumismatics

the copper in the coin tones causing the coin to take on an orange-ish color

ONETHREE

Gotcha. Thanks.

MrEureka

<< You never see orange peel on silver or nickel coins, only on copper and gold. Any guesses why? >>

Maybe because it is softer?

That seems likely to be part of the answer. But how does the softness of the planchet translate into an effect that seems caused by the dies?

MrEureka

the copper in the coin tones causing the coin to take on an orange-ish color

"Orange peel" refers to the texture of the coin, not the color. Take a look at the fields of the 1899 $5 above.

LanLord

How much you wanna bet some SOB can do it with a laser.

CalGold

<< <i>But how does the softness of the planchet translate into an effect that seems caused by the dies? >>



There is almost no relief to the orange peel texture. Perhaps it just does not strike up on the harder silver and nickel planchets.

CG

MrEureka

There is almost no relief to the orange peel texture. Perhaps it just does not strike up on the harder silver and nickel planchets.

If the metal can flow into the deepest devices of the dies, it can certainly fill any shallow die imperfections that might cause the orange peel.

EagleEye

Orange-peel has nothing to do with the color, it is the surface texture. I never thought about no nickel or silver with the effect. Perhaps it is effaced quickly from the die face with the harder metal planchets, perhaps it is done on purpose for copper and gold., although I doubt it.

Brilliant obvservation Mr. Eureka, what do you think?

MrEureka

Is it possible that the orange peel is the result of the dies being less hardened than usual? (Perhaps a proof die intended to coin a relatively small number of soft planchets wouldn't need to be as hard.)

And a related question...

Does the process of striking coins further harden the dies? (If so, it would explain why the orange peel disappears as the dies are used.)

mgoodm3

CalGold

Logically. What about striking pressure differences? Higher pressure on the silver and nickel coin presses obliterating the ripple effect?

CG

PS nice photo of the proof IHC.

CG

MrEureka

What about striking pressure differences? Higher pressure on the silver and nickel coin presses obliterating the ripple effect?

If the ripple effect is on the die, the higher pressure would maximize the visibility of the ripples.

Newmismatist

<< <i>The truth is that no one really knows what causes it (although a lot of people will claim they know). Due to the wave-like nature of orangepeel, I have begun to suspect that it is a function of multiple strikes from a fresh, uneroded die. Perhaps we should commission a study with Ron Landis. >>



The truth is that it's from the hardening process of the die - they die either expands when heated and then shrinks when it cools thus causing the wavy rippling effect - it only last fro the first few strikes from the die as the striking pressure and metal against metal wears away this very thin delicate surface of the die - plus for proofs, they dies are polished after a certain number of impressions to maintain the mirrored surfaces on the die. So a coin with orange peel surfaces is an early strike coin.

MrEureka

Ron - Why don't silver and nickel coins have orange peel?

CalGold

<< <i>(Perhaps a proof die intended to coin a relatively small number of soft planchets wouldn't need to be as hard.) >>



Proof IHC were struck by the thousands and each received multiple strikings.

CG

MrEureka

Proof IHC were struck by the thousands and each received multiple strikings.

Sure, but each proof die may have only coined a thousand coins, compared to perhaps 100,000 or more from a business strike die.

CalGold

If the proof dies had rippled due to contraction during the cooling stage of the hardening process, why weren't they relapped to smooth them?

CG

CaptHenway

<< <i>Ron - Why don't silver and nickel coins have orange peel? >>



Just a wild guess--perhaps the heat generated by multiple successive strikes was sufficient to melt the surface of the copper and gold, causing it to ripple, but not the silver and nickel?

Whose got a chart of melting points for copper, gold, silver and nickel?

TD

TwoSides2aCoin

A numismatic bump because I learned a lot from this thread.

CaptHenway

ttt

MrEureka

Just a wild guess--perhaps the heat generated by multiple successive strikes was sufficient to melt the surface of the copper and gold, causing it to ripple, but not the silver and nickel?

Tom - If that was the case, the orange peel would appear on all strikes, not just the early ones. And we know that the orange peel is exclusive to early strikes because the orange peeled coins are more cameo'd and more deeply mirrored than later strikes.

And to Regulated, I believe I've seen orange peeled 1891-2 business strike gold, but the coins were so PL that they almost looked proof. So I believe that the orange peel is a function of die preparation, not of multiple strikes, despite what we have discussed privately.

Newmismatist

<< <i>Ron - Why don't silver and nickel coins have orange peel? >>



Andy - I don't know for sure, but my WAG is that both silver and nickel are harder than copper or gold (I know for sure that they are ALL harder than gold) - I think we're starting to get into the realm of Physics and metalergy and that's a bit beyond my level of education - I know that stiking pressure results in metal flow on the planchet, that proof planchets are polished before striking to give them a mirror surface, multiple strikes provide the sharpness & squared rims on the coins and that in the 19th & 1st half of the 20th century that cameos are only on the first few early strikes of the proof coinage and then dissipate so that the cameo look disappears Also, there's NO cameos on Matte proofs and I've never seen orange peel on a Matte Proof, either gold or copper.



<< <i>f the proof dies had rippled due to contraction during the cooling stage of the hardening process, why weren't they relapped to smooth them? >>



CalGold - Don't know why they didn't lap the dies - but if they had immediately after the hardening process, it should have removed that microscopic ripple effect and as you see orange peel surface IHC proofs and Liberty Head proof Gold (19th and early 20th century) it has to be the way the initial dies were prepared - I don't recall seeing this effect on proof copper after the recommenced proof coinage in 1936, so my best "guess" is that the die preparation changed - there were new employees and it had been nearly 30 years since the last copper and gold coins that did exhibit orange peel surfaces had been struck (1909 Proof IHCs and 1908 Proof Liberty gold)

RWB

There are several letters by engraver Charles Barber discussing a change in die radius that occurred during hardening of the dies. This was a common problem in preparing the dies for use. However, none of the letters say anything about changes in the die surface being caused by this.

One way to analyze the problem is to list all the specimens identified with "orange peel" (or any other citrus fruit peel...). For each specimen, identify the characteristics of the surface (fields only, fields and portrait, portrait only, etc.) Last, note the differences between how the effect is portrayed on different specimens. The result is a list of commonalities and exceptions; then look for a known process that can produce these results without introducing others that are not present on the specimens.

(My "seat of the pants" thought is that "orange peel" is created by mechanical "chatter" during basining or possibly polishing of the dies.)

LeeG

"Super" info guy's! Much appreciated. I think this is "Orange Peel" on a 1909 Lincoln Cent?