Featured Luster: A guide for Beginners

Posted this in another thread, but I think its important for beginners to read and know, so I'll add a bit more and start a new thread for it.

Ok, first we're going to start with seeing the cartwheel. This can be tricky at first, because it takes just the right wrist movement to be able to move the coin and get the fluid cartwheel effect on the luster. Once you get it though, you will appreciate the beauty of it! Go get a slabbed, uncirculated coin (by a Top TPG - PCGS or NGC) and a strong light source. Hold the coin at an angle, so that it reflects the light. You should see the coin shining. Now, slowly and gradually, turn the coin. Notice the shine move? That is what we call cartwheel luster - if you turn the coin in the right way, the "spokes" of luster will appear to rotate around the coin like a cartwheel. Practice at this until you can see the cartwheel luster. Practice at this before reading the rest of this thread. Practice at this before buying anymore coins. If you can't see and discern luster, you can't properly grade, evaluate, or purchase coins.

Now, what causes this luster? When a coin is struck, the metal flows up into the recesses in the die, filling out the details and causing raised areas, which we see as devices, letters, etc. As it flows, the metal wears on the die; because the metal flows the same way each time, it will wear "grooves" into the die. I say "grooves" because I can't think of a better way to describe it - in numismatic parlance we call them flow lines. These microscopic lines reflect light in every direction, causing the diffuse shine that we call luster. Because luster is caused by wear on the die, later die states often have better luster. A brand new die will occassionally even be prooflike - having a mirrored surface and no cartwheeling luster. These prooflike coins are highly prized by collectors. As the die wears, the flowlines become etched into the die. The striking of coins wears the die down, often softening the details, until finally you get a late die state coin. By this point, the flowlines are strongly etched into the die, and you will sometimes get incredibly flashy luster.

When a coin is cleaned, this microscopic surface of the coin is disturbed. Depending on the method used to clean the coin, different disturbances are noted. This is one way we can tell how a coin was cleaned - baking soda or dipping will affect a coin differently than a wire brush or polish or whizzing, some of the most common ways to clean a coin.

There isn't really a single definition for a polished coin, its more of a catchall phrase, and can include wire brush, baking soda, or other methods. Whizzing, however, has a very specific meaning and a very specific look. Whizzing refers to when someone takes a rotating tool, such as a dentist's drill or a dremel, attaches a wire brush, sander, or polishing head, and goes at the coin. It gets its name from the "whizzing" sound this makes. If you are familiar with these tools, you can imagine the look this creates on a coin, although an expertly done whizzing can be hard to detect.

Taking a brush to a coin (wire or otherwise) creates a much different look. It usually has a large number of parallel lines, or groups of parallel lines in different directions. Usually, these polish lines will go over devices - if a line goes from the field, over a device, and back into the field uninterrupted, you can usually safely bet that it is a post-mint hairline or cleaning mark. Notice also that cleaning lines are recessed into the surface of the coin - the wire brush is intended to move and remove surface metal. Distinguishing raised versus recessed lines in the surface of the coin is tricky, but with proper lighting and experience, you can do it.

Both polishing and whizzing a coin have the same intended affect - to simulate original luster. This is why understanding luster, how it looks, and how its created, are so important - if you don't know what real luster looks like, you will never be able to discern artificial luster.

When you hold and rotate a polished coin under the light, in the same way you held your slabbed coins, you might at first see something that strongly simulates natural luster. But continue to rotate, and notice how differently it behaves. On a cleaned coin, because the polish lines all go in the same direction, quite often the luster will apear very strong in a particular direction. You must hold the coin just right to see it sometimes, and sometimes it is immediately obvious. It will glow unnaturally, and I'm sorry that I can't explain it better - but being familiar with natural luster, you will notice that it just doesn't look right. Experience is one of the best aids to determining this - hence my recommendation to examine and study numerous slabbed coins, to understand natural luster.

As you begin to learn and understand luster, you will see differences in the luster between different coins. I am going to use Franklin halves as an example, since that is the series I am most familiar with. There are several different kinds of luster - there is flashy, booming, dripping luster. This sort of luster makes the coin look like it is wet almost, with strong reflection and great luster. In the old school technical grading, better luster like this is required for a higher grade (it really begins to be important in differentiating a 64 from a 65 or higher). The 1950 Franklin half is known for this booming luster, as illustrated on my coin below.


Next we have average luster. This type of luster definitely cartwheels, and is pleasing to the eye. Its not booming though, like the coin above. My 1952D is a good example of average luster.


Finally, we have the creamy, subdued luster of my 1950D. Some coins just never have the great luster of other dates. These differences are important to a specialist in a series, because when you can find a 1950D with booming luster, you know you have a special coin.



Well, I hope that helps you. The best thing to do is examine as many coins as you can. Good luck!

Jason, aka physics-fan3.14

 

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Thanks for sharing! This helped me instantly.

 

Very glad to hear that. And thanks for the nomination, speedy.

 

I wanted to nominate this post in my original thread but didn't want the nomination to go to me. Anyway, I see the difference between pics 1 and 3, and 2 and 3; however, I don't see much, if any difference between pics 1 and 2. I know.....it's the beginner in me! When I think of cartwheel luster I can see it as I rotate the coin on two axes, both vertical and horizontal.

I'm going to "try" and illustrate what I want to convey with the standard keys on a computer keyboard. When I think of cartwheel luster, I think of something like this (looking horizontal where c equals the center of the coin)>c<, what you describe as polished flow lines running from the fields through the devices and back into the opposite field or edge, would look like this =c=?

What I typically notice is a 'flat' (kind of, all over the coin, and maybe in parallel lines across the entire diameter of the coin, not emitting from the center of the radius) consistent luster, no cartwheel. There is "shininess" across the entire face of the coin, but no noticeable cartwheel. Is this always an indication of a polished coin?

 

Feel free to nominate this thread, xtrmbrdr, I won't mind at all

To answer your questions: The actual shape of the "spokes" on the "cartwheel" will vary by coin, and by series. This is dependent on the shape of the coin, how the metal flows, any basining done, textured fields, and a number of other things. The main idea is that it should emanate from a central location and rotate with the proper movement. The luster on a Buffalo nickel, for example, will behave in a very different manner than the luster on a Morgan or Franklin.

What you describe as "flat" and unifromly across the coin sounds like how I might describe polishing. If it shows up very strongly when held in one direction, but doesn't rotate and seems to disappear at a different angle, chances are you are looking at hairlines due to cleaning. To illustrate, take a look at this French Indochine 50 cents. Notice how in the first picture, the coin looks very nice. There is cartwheel luster around the outside of the wreath, but not really inside. Look now at the second picture, how suddenly at the right angle, a whole bunch of parallel lines show up and it seems to glow. This coin has been very harshly cleaned inside the wreath.

 

Good article on luster, and what the difference is between mint luster and shine.
When it comes to proof coins, how could one tell if the polished planchet has been repolished?

 

What exactly do you mean by this? You mean, how can you tell if the proof coin has been cleaned (post mint)? Or how can you tell if the proof die was repolished? Or something else?

 

Proof coins do not have the cartwheel effect, so how could one tell if a coin was polished expertly enough to seem to be a proof coin? or if a proof coin acquired what some might consider ugly toning, (corrosion) and was repolished?
I work in a shop where mirror finishes are regularly put on different metals, so thats probably why the question arose in my mind.

 

Bravo! I've tried to explain this many times, you did a better job by a mile!

 

Even a proof has flow lines. Polishing a proof with leave obvious signs, even more so than a business strike.

 

Okie, I understand what you're getting at now. A proof is actually much easier to notice polishing or cleaning on, because the mirror finishes are very sensitive to disturbances. On modern or cameo proofs, the devices do actually appear to have luster. Just wanted to point that out. A proof coin will have several characteristics which differentiate it from a business strike coin, without ever looking at the luster - because a proof (by definition) is struck at least twice, the details are much stronger on a proof coin. The rims are also squared and sharp, as opposed to the rounded edges of a normal business strike.

Because the planchets for proofs are burnished before striking, it is unlikely that polishing after striking will produce the same mirrored finish. Especially in the recessed areas, or protected areas inside letters, for example, the polishing will not be able to get into every crack or crevice on the coin.

If a proof coin is cleaned by wiping or any mechanical removal of surface corrosion, toning, etc., is attempted, the mirrors are quickly ruined. Many early collectors would do just that - wipe their coins clean occassionally. This is why many proof coins are "hairlined" - and their grade suffers accordingly.

 

Just wanted to add and elaborate that Bad Thad is correct about proofs having flowlines. They are just much harder to see, and usually are only evident on lower quality proofs or later die states. Because for much of numismatic history proof dies were only used for a few hundred or maybe thousand coins, they rarely ever got to this state. As the mirror finish of the die begins to wear away through repeated striking, the flow lines which produce luster will begin to appear. You will notice on these that the mirrors appear more shallow. This is the same process that turns a DMPL into a PL, and then finally into a normal coin - eventually the mirrors become less deep.

 

Excellent post Jason, the French Indochine 50 cents perfectly illustrates what you have been trying to convey. I see it perfectly now.

So, (lol) I headed out to the garage, put a dime I had dipped to death in the vice, started with a wire brush for the Dremel, looked a little black or burnt in the center, went to a stiff nylon brush, looked better but still not too good. Ok, now what, ahhh yes the buffing wheel. Wow looks much better. Now for a bit of liquid polish and the buffing wheel again. WOW! This coin looks brand new to the naked eye. Magnified was a different story, looked like the second picture of the French Indochine 50 cent, except all across the coin.

I guess the unanswerable question is, why do this? Your French Indochine 50 cent would look fantastic without the polishing. For what I paid for the Morgan, just in melt, there is NO WAY anyone could make money doing this for non key coins, at least for what I consider my time worth.

AWESOME post, thanks. More experimentation to come from X's garage lol.

 

Perhaps another set of photos of a different series will help illustrate what the OP is saying. Photographing luster is one of the most difficult things to accomplish IMO. In hand, the difference between booming and average luster is clearly evident, but in photos, the difference is extremely difficult to represent. Here are photos of Jefferson Nickels with Booming, Average, and Satin luster.

BOOMING LUSTER
​

AVERAGE LUSTER
​

SATIN LUSTER
​

I tried to use virtually untoned coins in my example because the presence of toning further complicates the appearance of luster in photographs. I hoped this helped.

 

quote"Because the planchets for proofs are burnished before striking, it is unlikely that polishing after striking will produce the same mirrored finish. Especially in the recessed areas, or protected areas inside letters, for example, the polishing will not be able to get into every crack or crevice on the coin."

Thank you, for the answer, it makes sense. It also is a good reminder to check expensive coins with a good loupe, keeping in mind what you wrote about luster and the cartwheel effect

 

Thanks Lehigh, now I have to figure out the difference between booming luster, average luster and satin luster lol.

I guess the overall lesson learned is that luster, at least a proper luster, cannot be determined adequately from pictures, especially from ebay, it can only be done in hand. I'm sure I could make my whizzed dime pictures look how I wanted them to look very easily. What's a 1994D AU whizzed dime worth on ebay? :whistle:

 

Good post, PhysPi!

I think that luster is the most under-appreciated feature of a coin. Not only is it difficult to be a good judge of, but it is also the key feature in grading most coins.

 

I agree 100%. I hold eye appeal the most important, but the two are dependent upon each other. A high grade mint state coin must have excellent luster in order to have superior eye appeal.

 

I think strike is also very important, and very underrated. Luster and strike seem to have gotten the short end of the stick in modern market grading.

 

gREAT LEARNING GOING ON HERE FOR ME.

But I've got to ask......What is Whizzed? It that like You'in therapy for a coin?