Featured Have you ever wondered what luster looks like?

Discussion in 'US Coins Forum' started by TypeCoin971793, Jan 23, 2019.

  1. Insider

    Insider Talent on loan from...

    physics-fan3.14, posted: "For those reading this thread who are unfamiliar with this term, please read the brief summary on wikipedia here: https://en.wikipedia.org/wiki/Chatoyancy

    A tiger's eye is one of the best examples of chatoyancy in gems. The key quote from the summary on wikipedia is this: The difference between the gem and a coin is that the fibres in a gem which reflect the light are all arranged in a parallel fashion. The ridges that produce cartwheel luster are arranged radially around the coin, converging on the center (usually, depending on the design). Thus, when you rotate the gem, you don't see a cartwheel - you see the chatoyancy as unidirectional. However, when you rotate the coin, you are changing which set of parallel lines you are reflecting light off of, according to which direction your light is angled.

    The principle which is creating the effect, that of light bouncing off microscopic disturbances, however, is exactly the same.

    A wheel mark, or hairlines from polishing, are absolutely going to be chatoyant as you mention. However, their stark unidirectional reflective pattern is the fundamental difference between that and natural luster - they don't have that cartwheel, and just as the gem, may be nearly invisible at the wrong angles. "Natural mint luster" should be radial, not unidirectional.

    Based on this explanation, and my extrapolation of the term to numismatic, I stand by my assertion that this word may have some application in this discussion."

    That's why I wrote: "Hold the coin rock steady to mimic chatoyancy with a coin." Then, the radials going from the center to 1 o'clock will line up with the radials going from the center to 7 o'clock. They line up in a basically parallel direction! It mimics the gem. I hope the term never gets into the numismatic lexicon. :D
     
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  3. RonSanderson

    RonSanderson Supporter! Supporter

    Will do. I need a little time to create four 1920x1920 images from the original larger images. I have access to the files but not my computer. Maybe in an hour or so.
     
  4. RonSanderson

    RonSanderson Supporter! Supporter

    Per request, these have been scaled down to the max size allowed here. Click to expand!

    F8AC45D1-0D0D-45DF-9879-385545B98E0A.jpeg


    BA2773CE-1005-4AD4-8D3C-6BF18CC79CFC.jpeg

    C4E2C619-6067-4486-AE45-95BD52BAEC3E.jpeg

    D402EAF0-BB6C-44D9-BEF8-4C0CF984A718.jpeg
     
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  5. physics-fan3.14

    physics-fan3.14 You got any more of them.... prooflikes?

    I'll be honest, I don't know what the value of this coin is. But if it were mine, I might consider dipping it and then taking another image of that area. But only if its a low value or common coin. I'm really curious to know how much that "rub" actually changed the metal structure, or how much of what we are seeing is a residual fingerprint.
     
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  6. GDJMSP

    GDJMSP Numismatist Moderator

    Thanks. The reason I asked for the still pics is so that the result of misalignment could be more easily seen on the rims.

    To understand what the dies being slightly misaligned does to the resulting coin, and why that causes a weaker strike, which results in a lower quality of luster, one must first understand that there are two ways for the dies to be misaligned. One is on the horizontal plane and the 2nd is on the vertical plane. Or, they can be misaligned in both directions at the same time.

    I can't draw pictures on a keyboard, so to make it easier to visualize things perhaps a couple pictures of a die as seen from its edge would help.

    die5.jpg

    die6.jpg


    As we can see from those 2 pics the highest point on the die is the fields, with the denticles being slightly lower and the outer edge of the rim being even lower than that. These things are the same on pretty much all dies, I'm merely using these pics above because they're the best pics I have to illustrate what I'm talking about.

    Now imagine 2 dies, one set down on top of the other. If the dies were perfectly aligned the outer edge of the fields (the high points) would line up perfectly with each other all the way around. And the surfaces of the fields on both dies would be touching each other everywhere. And the denticles and outer edges of the rims would line up with their opposites as well. And if a coin were struck then it would be well struck, assuming the pressure was correct, because everything was lined up just right. Metal would flow exactly as it was intended to and a high quality of luster would be produced on the coin.

    But if there was a slight misalignment in the vertical plane then the edge of the fields of one die would overlap the denticles of the other die on both sides, left and right. This would result in the rims being wider on one side of the coin and narrower on the the other. All by itself this results in the metal not flowing the way it's supposed to and thus producing a lower quality of luster because the metal wouldn't all go where it's supposed to.

    And if there was misalignment in the horizontal plane, and the dies were lowered one on top of the other, then the fields of the dies would be touching on one side but there would be a thin gap between the fields of the two dies on the other side. And if that were the case then of course there would not be as much pressure exerted upon the planchet as there was supposed to be, which would also result in less metal flow, a weaker strike and lower quality of luster.

    And if the dies were misaligned in both directions, horizontally and vertically, then the luster would doubly affected, weakened.

    Taking all of that into consideration, looking at the 1939 coin we can see that the width of the rims are pretty close to equal all the way around. They're not perfect but they are pretty close. And they also appear to be of roughly equal height all the way around. This means those dies were pretty well aligned with each other in both directions, and that produced a higher quality of luster on that coin.

    But when we look at the 1941 coin it is obvious that the rims on both obv and rev are a good bit wider on one side than the other, (comparing left and right), and they also appear slightly higher on one side than the other, (again comparing left and right). This tells us the dies were not properly aligned, in both directions, which explains why the coin has a much lower quality of luster.

    And the point that you brought up Mike that if that's what defines misaligned dies then most coins are that way, I readily agree, most coins are indeed that way ! And it stands to reason that they are because finding coins that are well struck and have high quality luster is pretty hard to do isn't it ? I mean if most coins were not struck with misaligned dies then far more of them would have that higher quality of luster.

    Coins that are struck with properly aligned dies is what produces the higher grades of coins. Properly aligned dies not only produce the higher quality of luster, they also produce coins that are well struck, and coins that well centered, all of of which are individual grading criteria. But few ever think about it enough to realize that all of that is caused by one single thing - properly aligned dies.

    And when we don't have properly aligned dies, well the '41 coin is an example of what we see.
     
  7. GDJMSP

    GDJMSP Numismatist Moderator

    It makes perfect sense. I've tried to explain it many, many times by using this simple illustration - /\/\/\/\/\/\/ - to simulate what luster looks like. And if you view that illustration and imagine the light striking those angled lines, at various points from the top to the bottom of the angled lines, it then becomes easier to also understand that before the light ever reaches our eyes that at least some of it can bounce from one line to another, and only then be reflected back to our eyes. This is what produces the diffused reflection of light, the wider beam of light if you will, that we see when we view a coin.

    You said it differently than I have many times in the past, but we are saying the same thing. It also explains why each type of coin has a different kind of luster than other coins. Because those lines are all different heights and widths on each type of coin. And we've seen that in all the pics that have been posted, including those of Proofs.
     
  8. Insider

    Insider Talent on loan from...

    IMO, neither of the dimes is struck with a misaligned die. ;)
     
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  9. GDJMSP

    GDJMSP Numismatist Moderator

    Well then you apparently have a different definition of misaligned dies than I do. Care to tell us what your definition is ?

    edit - I guess I should have added that I readily agree there are very different degrees, some of them extreme, of just how far dies can be misaligned.
     
  10. RonSanderson

    RonSanderson Supporter! Supporter

    I’m making some popcorn and settling in for some interesting give-and-take! This is already an education worth the $25 I paid for these dimes.
     
    Last edited: Jan 31, 2019
    Insider, 1916D10C and -jeffB like this.
  11. physics-fan3.14

    physics-fan3.14 You got any more of them.... prooflikes?

    I agree. Neither of these coins show misalignment, and certainly not to the degree that the luster would be affected. (I'm not convinced that die misalignment would actually affect luster the way that Doug is claiming - I will look into the matter more and see what I can find)
     
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  12. Insider

    Insider Talent on loan from...

    And something else would be nice to research...

    I've been told that in order to be considered struck "off-center," part of the design must be missing - otherwise, it is considered to be just a misaligned die! The rim is not included as it is not a part of the design. This makes no sense to me.
     
  13. Off-center requires part of the design on BOTH sides to be missing. Otherwise, it is just a MAD
     
  14. GDJMSP

    GDJMSP Numismatist Moderator

    I readily agree that the 1939 was not struck with misaligned dies - and said so.

    But the 1941 coin, if the dies were properly aligned, then the width and height of the rims would be equal all the way around. They are obviously not. And to me, that can only mean one thing - the dies were misaligned.

    But if you guys wish to disagree, OK. Then please show me a picture of a coin that was struck with misaligned dies. Or, describe in words how you define misaligned dies. So that I can understand what you're talking about.

    First off, can we agree that the quality of luster on a given coin is a function of pressure because pressure is what creates the metal flow, and metal flow is what creates luster to begin with ?

    If we can agree on that, then we need to agree or disagree that there are a few things that can affect the pressure being exerted on a planchet. The most obvious of course would be the pressure setting on the press. Granted, that setting can vary and often does for a couple of different reasons. As has been mentioned previously sometimes one mint will use a lower pressure setting than another to extend die life. Sometimes it is an accident, somebody on the floor makes a mistake with the pressure adjustment.

    Another would be die spacing - which is defined by how far apart the dies are set to be in the press. Make the space too far apart and not as much pressure will be exerted. This setting too can be deliberate or accidental. And less pressure means a lower quality of luster - assuming we agree on my first comment.

    Yet another would be a planchet that is too thin, or too thick. Either one will affect the resulting coin and its luster because either one will affect the amount of pressure being applied to the planchet. Too thin and the quality of luster will be lower, too thick and the quality of luster will be higher, but there will also be finning produced on the coin, to varying degrees, as a result of the higher pressure.

    And lastly, proper or improper die alignment. How proper or improper die alignment affects pressure should be obvious. Proper pressure is only applied when and if the dies both come together on the planchet in the right places. In the vertical plane, if high points and low points on one die don't line up just right with high points and low points on the other die then proper pressure cannot be applied. This is simple logic.

    In the horizontal plane, if one die is set slightly out or parallel with the other die, or if both dies are set slightly out of dead level or plumb as the case may be ( as in horizontal vs vertical presses) then the faces of the dies simply cannot come together as they were designed to do. It is impossible because they will further apart on one side than they are on the other. And if they do not come together as designed then this exerts less pressure. And less pressure results in a lower quality of luster. Again this is simple logic.

    Edit -

    Just realized I left something out here, I forgot to mention die wear. Die wear most definitely affects the quality of luster. Coins with the highest quality of luster are struck with fairly fresh dies, dies that have little to no die wear. And the more die wear a die has the lower the quality of luster will be.

    And yes, I realize there are those who disagree with that. But they fail to take into account that uniformity in the flow lines is what produces the highest quality of luster. And die wear by definition reduces uniformity.

    Now if you wish to disagree, please do. But please explain the how and why.
     
    Last edited: Feb 1, 2019
  15. messydesk

    messydesk Well-Known Member

    That depends on how they were prepared. Not all dies are polished to a mirror finish before being put into service. 1921-S Morgans don't exist in PL, but the early die states can have a satiny or frosty luster before the dies start wearing (quickly) through the cartwheel luster to the mushy orange peel luster typical of 21-S Morgans. In all cases, die wear produces flow lines, which give anisotropic reflection as described above. Whether the dies are produced to initially have high specular reflection (mirrored surfaces) or diffuse reflection (frosty cameos, satiny surfaces) doesn't matter.

    So to answer your question, a fresh satiny die will produce satiny coins until it produces "cartwheely" coins, and a mirrored die will produce mirrored coins until it produces "cartwheely" coins, but a mirrored die won't eventually produce satiny coins, nor will a satiny die eventually produce mirrored coins.
     
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  16. RonSanderson

    RonSanderson Supporter! Supporter

    Thanks. One can conclude, then, that a satiny business strike is not quite comparable to an early Cameo Proof strike. I have been considering whether this is a stage all new business dies go through. If it were so, a satin stage business strike would be just as uncommon and rare as an early Cameo Proof. (With attendant premium pricing.)

    Still, looking at the surface, these finishes would not be produced for long, so maybe there should be a comparable interest in them and a similar premium.

    I will volunteer my dime as the discovery coin!
     
    Last edited: Feb 1, 2019
  17. messydesk

    messydesk Well-Known Member

    Perhaps, but a DMPL or non-modern cameo proof has much more "wow" factor. I chose 21-S Morgans as an example, because of this coin I bought a year or so ago. I knew it was a super early strike and a rather special 21-S, but it's not so obvious to most that don't really know the series. Sharp, satiny, more diffuse reflection than anisotropic. When I showed this to some Morgan specialists, I covered the label and had them guess the grade, so that it didn't look like all I was covering was the mint mark. They were shocked when they looked at the reverse and saw the S.

    [​IMG]
     
  18. Insider

    Insider Talent on loan from...

    GDJMSP, posted: "...But the 1941 coin, if the dies were properly aligned, then the width and height of the rims would be equal all the way around. They are obviously not. And to me, that can only mean one thing - the dies were misaligned.

    Actually, there are several reasons a coin's rims may not be full or equal. It has nothing to do with the die alignment.

    EDIT: After reading the rest of your post, I see that you addressed those issues and I can delete my original comments.
     
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  19. Pickin and Grinin

    Pickin and Grinin Well-Known Member

    That's an amazing looking 21S Messydesk.
    I see know what you were saying.
     
  20. GDJMSP

    GDJMSP Numismatist Moderator

    @Insider I'd still like to see an example of what you think a coin struck with misaligned dies looks like. And, your verbal definition of misaligned dies.
     
  21. Insider

    Insider Talent on loan from...

    I'll search my pocket change jar at work and take an image. The internet is full of them + definitions but I'll get on it tthiscoming week.
     
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