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What is Orange Peel?
EagleEye
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Orange peel is found on the mirrored fields of Proof gold and copper coins. The effect is simulated on the Proof Buffalo bullion coin. It was earlier thought to be a product of die crystallization and shrinkage in the heat- treating process of the dies. However, it is not seen on nickel or silver coins. Why is that?
The answer is that the galvanized look is due to too high an annealing temperature for the gold and copper blanks. The annealing furnace was set for nickel and silver which required higher temps. You see the effect on Proofs because the mirrored surface makes it very easy to see. Occasionally you can spot it on toned copper as well.
The answer is that the galvanized look is due to too high an annealing temperature for the gold and copper blanks. The annealing furnace was set for nickel and silver which required higher temps. You see the effect on Proofs because the mirrored surface makes it very easy to see. Occasionally you can spot it on toned copper as well.
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Comments
Note: I was told
I'd really like to hear CaptHenway's or Fred Weinberg's take on this.
An old and not very good image example
Not to be confused with "peach fuzz" flow lines on mint state copper
So, is this orange peel, or whizzing, or something else?
I was trying to learn all I could before buying my first (and only) Proof IHC.
Thanks to those who posted pics. Clearer understanding now.
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That is not "Orange Peel".
<< <i>I was told that, on gold, it has to do with die suction and a soft metal. As copper is soft, I'd imagine the same phenomenon occurs. Silver and nickel are much harder metals.
Note: I was told
I'd really like to hear CaptHenway's or Fred Weinberg's take on this. >>
this is what i was told as well. and something about the metal involved as well. (fwiw)
I'm not qualified to define the term, but whatever the OP's intent, it is certainly in common use with reference to Peace Dollars.
To me, it looks like this:
Was it all theory or was Chris able to prove it??
Obviously there is some lack of consensus.
Is it a "look", a minting process, a method of manufacture, die state, or what? Who sets the definition? Is it simply a descriptive term or does it imply something specific? What did Chris Pilliod say about it?
Metalurgy, crystal size, alloys, annealing, cold flow, strain hardening...... these are reasonably advanced engineering concepts. Maybe this topic doesn't lend itself a simplified chatroom answer. If I hear Rick correctly, he's saying the official "orange peel" look is a result of properties imparted to gold or copper planchets during the annealing process. What I'm showing above on the Peace Dollar is a grainy unofficial "oragne peel" look theoretically imparted to a regular silver planchet by a late die-state die.
Look at galvanized steel. It has irregular geometric shapes in the surface. That is what we are talking about seeing on the surface of gold and copper Proofs.
--Severian the Lame
<< <i>1924 peace dollars can have an orange peel surface. Vamworld calls it "die fatigue":
That is what I call "die erosion." It repeats from coin to coin as it slowly gets worse. If some collectors want to call it "orange peel," I can't stop them.
IMHO, the term, "orange peel" refers to a specific effect (probably) caused during striking, when the surface of the coin ripples.
I have never heard of this term being thought of as a color before.
Eric
<< <i>
Agreed. This is an excellent picture of the rippled effect.
Can be bright or toned. Doesn't matter.
AngryTurtle above raises an important point about whether each coin from the same dies show the effect differently.
New collectors, please educate yourself before spending money on coins; there are people who believe that using numismatic knowledge to rip the naïve is what this hobby is all about.
1. Is this orange peel only found on Proof coins?
2. Is the orange peel a texture or does it just look like a texture?
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<< <i>Define "Orange Peel".
Obviously there is some lack of consensus.
Is it a "look", a minting process, a method of manufacture, die state, or what? Who sets the definition? Is it simply a descriptive term or does it imply something specific? What did Chris Pilliod say about it?
Metalurgy, crystal size, alloys, annealing, cold flow, strain hardening...... these are reasonably advanced engineering concepts. Maybe this topic doesn't lend itself a simplified chatroom answer. If I hear Rick correctly, he's saying the official "orange peel" look is a result of properties imparted to gold or copper planchets during the annealing process. What I'm showing above on the Peace Dollar is a grainy unofficial "oragne peel" look theoretically imparted to a regular silver planchet by a late die-state die. >>
Re: '24 P$1. Stippling is not "orange peel" I might be getting too semantic here. It presents as an "orange peel effect" but doesn't result from the same physical process.
1) Who is Chris Pilliod? Sounds like he knows something many of us don't.
2) I can't accept EagleEye's hypothesis of annealing issues unless he can explain how such a consistent pattern of stippling on a planchet can survive the intense pressures of the striking process.
As I expected, CaptH makes the most sense to me. I'd still like to hear Fred Weinberg's take on this. He's spent more time on the floor of the Mint(s) than the Superintendents.
Someone go to his table at Long Beach and ask him about this.
Edit: Unfortunately, it appears that the lighting is so different that a reasonable comparison can't be made...obviously there could have been many coins struck between the striking of these two coins.
We coin nerds can claim knowledge by looking at coins, but without the real world experience in other related subjects like metal production, we are only making guesses. Chris, if you know him, doesn't guess.
To further the discussion, I see orange peel on MS Indians sometimes. The surface looks like galvanized steel. It would be interesting to see if orange peel surfaces on Proof gold and copper have actual elevation or it is an optical illusion. A SEM test would show any differences in elevation clearly since it does not show reflectivity.
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How about foreign coins? If orange peel comes from too high an annealing temp, then what if a mint used the proper temp? Are there British examples of orange peel in Victorian era Proof gold and copper?
Anyone seen this effect on later date Coronet copper proofs? Classic Head proofs? Business strikes? The consistency of the annealing result may be different (less precise, more primitive?) for pre-steam press coins. The lower die pressure may result in less obliteration of any poor annealing results.
I understand Fred W. is at his table at Long Beach currently examining a Wreath 1c claimed to be 100% off-center because others consider it to be a 100% clip.
Those who claimed to see it said it won't grade.
<< <i>I understand Fred W. is at his table at Long Beach currently examining a Wreath 1c claimed to be 100% off-center because others consider it to be a 100% clip.
Those who claimed to see it said it won't grade.
Somebody do a specific gravity test on it.........
<< <i>Chris Pilliod is the President of the Fly-In club and his profession is metallurgist. He has great insight on how dies are made and metal properties. I respect his opinion over other numismatists, because he has knowledge in both numismatics and metallurgy and die making.
We coin nerds can claim knowledge by looking at coins, but without the real world experience in other related subjects like metal production, we are only making guesses. Chris, if you know him, doesn't guess.
To further the discussion, I see orange peel on MS Indians sometimes. The surface looks like galvanized steel. It would be interesting to see if orange peel surfaces on Proof gold and copper have actual elevation or it is an optical illusion. A SEM test would show any differences in elevation clearly since it does not show reflectivity. >>
Can't argue with his expertise, but I'd still like to know why the stippling (assumedly, from what you say), in or on the planchet isn't obliterated by the pressure of the dies on the planchet. Double-struck proofs especially.
Like I said in the OP, my thinking for a long time was that the orange peel was in the die. But then, why is it not found on nickel and silver coins?
<< <i>The orange peel is a crystallization of the metal in the planchet. The various grains of the metal is orientated in a multitude of different angles. The surface looks like raised, angled geometric shapes, right? Is it raised or an optical illusion?
Like I said in the OP, my thinking for a long time was that the orange peel was in the die. But then, why is it not found on nickel and silver coins? >>
Has Mr. Pilliod ever imaged (viewed) a true 19th c. "orange peel" gold or copper proof under a scanning electron microscope or a 1000x+ metallurgical scope?
Also, at those magnifications he should also be able to discern whether 19th c. silver and nickel proofs have a slight hint of the orange peel effect which the naked eye is unable to discern. If SEMs still cause a surface "burn" like they did in the late 1970s, you could sacrifice some PF62/3 coins which shouldn't cause any discernible harm to the proof's fields.
That the description "orange peel" has been used in our industry does not necessarily constrain us to rooting the numismatic definition of the term to any other industry in particular. This is especially true since each of the other references characterize the unintended result of poor process control, rather than a successful outcome of their respective processes.
I suspect that, because it is referenced in so many other industries, and seems consistently used as a descriptor of unintended surface texture, that was likely the intent of the original reference in our industry as well.
I work for an OEM making products of steel, aluminum, zinc, bronze, polyethylene, nylon, urethanes, and paints, and have seen the term used universally to describe texture across all disciplines. I personally think it should be similarly applied here in numismatics as well.
Adherents to the notion that the orange peel effect is attributable direclty to the poor annealing of the planchet stock, and applies only to copper and gold coins, to the exclusion of silver and nickel, should rethink their position as the grain size in a planchet will be coarser than normal for any metal that is insufficiently annealed, resulting in the abnormalities cited in several examples above.
<< <i>While "orange peel" is a recognized term in several different industries, notably metal forging, plastic injection molding, painting, metal casting, etc, the root causes for it are not all consistent. It can result from the uneven flow of insufficiently annealed metal, eroded tooling, premature cooling of the flow front in a molded plastic part, premature "skinning" of paint, contamination of casting sand, etc.
That the description "orange peel" has been used in our industry does not necessarily constrain us to rooting the numismatic definition of the term to any other industry in particular. This is especially true since each of the other references characterize the unintended result of poor process control, rather than a successful outcome of their respective processes.
I suspect that, because it is referenced in so many other industries, and seems consistently used as a descriptor of unintended surface texture, that was likely the intent of the original reference in our industry as well.
I work for an OEM making products of steel, aluminum, zinc, bronze, polyethylene, nylon, urethanes, and paints, and have seen the term used universally to describe texture across all disciplines. I personally think it should be similarly applied here in numismatics as well.
Adherents to the notion that the orange peel effect is attributable direclty to the poor annealing of the planchet stock, and applies only to copper and gold coins, to the exclusion of silver and nickel, should rethink their position as the grain size in a planchet will be coarser than normal for any metal that is insufficiently annealed, resulting in the abnormalities cited in several examples above. >>
Better then any if my first couple posts, welcome to the forum
Welcome to the forum.
I understand there are different types and causes, which is why I want to limit the discussion the 19th century gold and bronze (as well as silver and nickel)
Since you are in the metals business, what are the proper annealing temperatures for bronze, copper-nickel, silver and gold in the typical coinage alloys?
<< <i>Adherents to the notion that the orange peel effect is attributable direclty to the poor annealing of the planchet stock, and applies only to copper and gold coins, to the exclusion of silver and nickel, should rethink their position as the grain size in a planchet will be coarser than normal for any metal that is insufficiently annealed, resulting in the abnormalities cited in several examples above.
Welcome to the forum.
I understand there are different types and causes, which is why I want to limit the discussion the 19th century gold and bronze (as well as silver and nickel)
Since you are in the metals business, what are the proper annealing temperatures for bronze, copper-nickel, silver and gold in the typical coinage alloys? >>
Good question which probably leans towards the science and phenomena of eutectics in some manner. The answer is most likely somewhere between their annealing temps used, time proximity to actually striking the coins, and die pressure used.
It's curious that silver wouldn't exhibit more "orange peel" given it has a lower MP than Au or Cu, which are very close (assuming they annealed using nickel as a worst case). I wonder if RWB has ever come across any early mint records on annealing temps, processes, etc.?
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