what causes cartwheel on some coins and not others?

1907Quarter

just wondering.

coinguy1

1907quarter - simply put, cartwheel luster is a result of light hitting and reflecting off of the surface of a coin. There are a number of factors that can affect and / or interfere with that process.

Among them are:

Toning or haze on the surface of a coin,

Differences in the designs of various coins, where the devices (such as the portrait of Liberty or whomever appears on the coin) might comprise a larger or different % of the coin's surface,

Metal flow from the way the coin was produced,

Subdued luster from storage, mishandling, or, in the case of circulated coins -circulation / wear,

Cleaning,

The light source being used

barberlover

I would say that on seated coinage at least 90 % of the coins that I've seen graded by pcgs and ngc as mint state are overgraded sliders and not mint state at all, many people I've talked to feel the same but probably wont say so here.

Les

CarlWohlforth

As CoinGuy1 says one reason is

<< <i>Metal flow from the way the coin was produced >>

. This can change as the dies wear. You can find Morgans with great cartwheel effect and others with none. The DMPL Morgans should not have a cartwheel effect if they have really deep mirror like fields.

edited to say: most proofs should not have that effect either. When people describe a proof coin as lustous I often wonder if the coin has good mirror like fields or if the person describing the coin doesn't really know what luster is.

Fairlaneman

Correct me if I am wrong on this. Its my understanding that the Cart Wheel effect gets a little better as the Die is used longer. True or False ?

Ken

clackamas

>>Correct me if I am wrong on this. Its my understanding that the Cart Wheel effect gets a little better as the Die is used longer. True or False ?

From what I have seen from countless rolls is that you can have coins from the same die, in the same roll, and get good cartwhell on one and not the other. But when you do find some coins with nice cartwheel you will usually find others (in a roll) and these typically are from the same die pair and from what I have seen these are typically new(er) dies. I think the metal composition plays apart as well as strike. It would be nice to know for sure what causes it.

BillJones

<< <i>I would say that on seated coinage at least 90 % of the coins that I've seen graded by pcgs and ngc as mint state are overgraded sliders and not mint state at all, many people I've talked to feel the same but probably wont say so here. >>



I'll say so here. It's darned hard to find a real Mint State seated coin in a PCGS or NGC holder. Most of them have a rub on Ms. Liberty's breasts, thighs andor knees. It’s made me think that most of all the REAL Mint State seated coins are either hiding in collections, or they are a lot scarcer that we have been led to believe.

I've seen a few seated coins with a flat spot at the knee that many not have struck off the coin at the time. But for the most part there are too many liberty seated sliders around that are getting credit as Mint State coins. Ditto for many scarcer gold pieces in grades up to and including MS-64.

As for the cartwheel question, coinguy 1 covered it pretty well. It has to do with the metal flow that the dies imparted upon the coin when it was struck and what has happened to the coin since then. Brand new or recently repolished dies can show “proof-like” surfaces which might have little or no cartwheel luster. Well used dies may have a duller sand-blasted looking luster, but it takes experience to tell the difference between that and coins that have cleaned or fooled with.

EVillageProwler

In principle, luster is caused by light reflecting off flow lines that were created as metal flows into the design details of the dies. Any coin that is made this way will have luster -- including proofs.

Of course, the state of the dies and the force of the strike upon the planchet (and relative to the hardness of the metal) will have a bearing on how pronounced the cartwheel luster is.

For example, a die that's been around the block will create a frosty texture to the surface of the coin. That, in turn, will allow for the appearance of greater radiance of light bouncing off the coin (because the surface is less smooth) as you swivel the coin.

A coin that's been struck from a highly polished die will, on the other hand, have a smoother surface. That means that the light will bounce off the coin with less of a scattering effect, thus giving the appearance of less radiance. That, in turn, means a less pronounced luster.

A nice DMPL Morgan Dollar should, and will, exhibit very nice cartwheel luster.

I think Mark Feld gave excellent reasons why a coin can develop impaired (or non-existent) luster.

EVP

CarlWohlforth

<< <i>A nice DMPL Morgan Dollar should, and will, exhibit very nice cartwheel luster >>



OK, to me cartwheel luster is when I tilt the coin under a light and the reflection rotates around the coin. This reflection looks like a bow tie. Most of us may not know what the wooden wheel of a cart looks like when the cart is moving quickly. When the wheel gets spinning the spokes blur and looks sort of like a bow tie.

Proof Like Morgans can have cartwheel luster. The surfaces are not deep mirrors. Deep Mirror Proof Like Morgans shouldn't have a pronounced cartwheel effect. There may be some luster but there really shouldn't be much, if any. If there are lots of flowlines the fields would not reflect perfectly like a mirror.

Anyway that is how I understand it.

1907Quarter

thanks to all who participated in this discussion. The ANA Grading book has a short paragraph on this. It gives 4 types. Satin(dull and uniform) frosty, brilliant and prooflike. Further examples(photos anyone?)of these would be I'm sure add to the thread!

Conder101

<< <i>Correct me if I am wrong on this. Its my understanding that the Cart Wheel effect gets a little better as the Die is used longer. True or False ? >>


True to a point.
Brand new dies that produce dmpl surfaces do not produce good luster. As the die starts to wear slightly it both develops its own flowlines and imparts flowlines on the coins it produces. It is these flowlines that produce the luster on the coin. As the flowlines gradually become heavier the coin becomes less prooflike and more lusturous. But at some pont the flowlines become large enough that the light scattering is no longer even and the coins begin to lose luster and just take in a satin appearance. If the die continues in use the flowlines become large enough to be easily visible to the naked eye and the surfaces develop an "orange peel" appearance. With even more wear to the dies heavy die wear lines begin to appear on the coin and details begin to become smeared and drawn out or doubled. The surfaces look rough with clearly visible radial lines and the coins look like mush.

1907Quarter

in other words, and correct me if I'm wrong Conder, there is indeed a general evolution from prooflike to frosted to satin. So if this is true, where does "brilliant" fit in?

Conder101

Yes it does evolve. Where "brilliant", "frosty", and "satin" fit in depends on how you define the terms. What one person calls frosty, someone else calls brilliant etc.

Baley

types of luster, from smoothest to roughest:

Proof or prooflike: smooth, mirror finish
Brilliant: not quite mirror, but no "texture" visible to naked eye
Satin: slightly more frosty, but still pretty smooth; silky or satiny look
Frosty: self explanitory, it's white and frosty!
Crunchy: Very frosty with texture and flow lines. (my favorite)

Fairlaneman

<< <i>types of luster, from smoothest to roughest:

Proof or prooflike: smooth, mirror finish
Brilliant: not quite mirror, but no "texture" visible to naked eye
Satin: slightly more frosty, but still pretty smooth; silky or satiny look
Frosty: self explanitory, it's white and frosty!
Crunchy: Very frosty with texture and flow lines. (my favorite) >>



Would you think the graders at PCGS or NGC would take the different types of luster into account when grading a coin ? I can see where they might give a coin the grade bump up for prooflike and a bump down for crunchy, nice term by the way. Outside of those two it probably would be just graded by the persons own preference.

Nice thread with excellent information.

Ken

Goldog63

I don't think they break it down like that. Exellent luster can be brilliant, satin, frosty etc.. Proof(like) coins are the only ones where the luster is less apparent (tho still there and still important). Luster breaks or a lack of luster such as a "dipped out" coins get knocked down

cladking

<< <i>

From what I have seen from countless rolls is that you can have coins from the same die, in the same roll, and get good cartwhell on one and not the other. But when you do find some coins with nice cartwheel you will usually find others (in a roll) and these typically are from the same die pair and from what I have seen these are typically new(er) dies. I think the metal composition plays apart as well as strike. It would be nice to know for sure what causes it. >>



There may be other phenomena at work here, but I think generally the
cause is planchet condition. Some planchets will be heavily marked, greasy,
or slightly thinner than others. Sometimes tiny differences in conditions will
result in huge differences in appearance.