What You Need to Know about Luster

[physics-fan3.14]

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

[Schatzy]

Great Job Jason!! (thumbs u (thumbs u

[PCcoins]

Of course I already knew that, but that was a great and interesting read!

 

 

This '57p has incredible booming luster!

 

[physics-fan3.14]

Of course I already knew that, but that was a great and interesting read!

 

 

I'm sure most of the regulars on here know all this, but its intended more for a beginner, or someone who doesn't really understand luster. And of course, it never hurts to review the basics

 

And in reply to your frankie: mmmmmmmmmm

[Bugmann1974]

To be perfectly honest I didn't know what "cartwheel" refered to. I absolutely have always known the difference between a coin with luster and a coin without, I just never had rotated a coin like that (untill just now!) But with the term being used so frequently I figured the subject would come up at some point.

 

I do know what booming luster is, I have an absolutly dripping Peace Dollar that I picked up recently.

 

I also knew all about flow lines, I have a CWT that has flow lines that you can see from 10 feet away. Not quite so microscopic

 

I guess I will have to post pictures when I get home from work.

 

Thanks for the article Jason!

[bsshog40]

Nice informative post there jason!!

[WoodenJefferson]

There ya go!

 

Good read.

 

I want to point out or add to Jason’s comments, that a coin that has “luster breaks” on the coins surface, especially in the fields, could indicate some types of wear characteristics. Also, luster that is still present around devices and lettering on a circulated coin, does at times, help in determining a specific grade, something like a post-mortem examination.

 

That’s how important luster on a coin can be.

 

Thanks again.

[RWB]

Wasn't he Batman's nemesis?

[Jim Beam]

Thank you, sir, for a very informative explanation of luster and how to interpret what it means. I found it to be very helpful and something I can actually experiment with to learn even more. Good job!

[praedator-migration]

Very informative Jason, thanks!

[Bugmann1974]

1923 Peace Dollar, Booming luster.

 

1864 Civil war token, This has heavy flow lines but my camera refused to focus on it tonight. In these old images of the coin that I took a while back you can see some of the flow lines in between the letters and the rim on the reverse of the coin. These flow lines are much more apparent in person. These dies were well wore out by the time the token was made.

[michael]

Very informative Jason, thanks!

 

 

(thumbs u

[Schatzy]

Awesome Post Jason!!

 

I just Nominated your post on cointalk!! You always have quality posts!!

[Oldtrader3]

Peace dollar with cartwheel luster.

[physics-fan3.14]

I thought I'd post the link to the Cointalk discussion. There were a couple of good questions and points raised, which also spawned a discussion ATS.

 

http://www.cointalk.com/forum/t58435/

http://forums.collectors.com/messageview.cfm?catid=26&threadid=727424

 

[supertooth]

Jason---- Am very glad to see you give a link to the post by Mike in Fl from ATS.

 

I had just asked both Woody and Lou to add their comments to this thread----as I thought their words added MUCH valuable information to this "luster" thread. An awful lot of knowledgable comments have been made and I do hope that Arch will put this one into the WYNTK archives. Thanks to all. Bob [supertooth]

[WoodenJefferson]

On another board, the question was posed, do LDS coins exhibit better luster than their EDS counterparts?

 

These were my comments:

 

I would not specifically point to Early Die States to impart more luster than a Late Die State or visa versa. Many factors come into play to create a coin with booming luster. From die preparation, to die standoff and striking pressures, all the way down to planchet preparation.

 

As the dies wear from repeated striking, flow lines radiating from a central point become a bit more pronounced on the coin, even eroding into the lettering and devices. Dies are normally removed from service long before coins become ugly, but I have seen modern Kennedy half dollars in the 80’s with severe LDS strikes. Even though the flow lines are significant and should by all rights create luster, the coin are actually ugly.

 

I do believe there is a happy medium with die wear and the amount of luster seen on a well struck coin.

 

When that happens, it’s magical.

[IGWT]

Bob asked that I add this post to the thread:

 

"With Mint State coins, luster is the result of light reflecting from the surface. As a coin is struck, the metal flows into the recesses of the die because of the pressure applied by the coining press. The metal flow is usually in a radial pattern, i.e., outward toward the rim. On some coins, these lines are all but invisible but are still present microscopically. The degree of luster is determined by how, and how intensely, light reflects from these flow lines. Sometimes this luster “cartwheels” around the fields (or background areas) of a coin as it is tilted back and forth under a good light source. Mint State luster is categorized in several ways: flat (flow lines are invisible to the unaided eye, as often happens when coins are struck from worn dies), satin (flow lines may be slightly visible but there is little cartwheel effect), frosty (flow lines are usually visible with a cartwheel effect, ranging from slight to heavy), semi-prooflike (light flow lines may be visible but most are not, being replaced by slightly mirrored fields that have a slight cartwheel effect), and prooflike (no flow lines are visible, with the fields now mirror-like, but with virtually no cartwheel effect). . . . Flow lines are present even on . . . brilliant Proofs, but only in microscopic form. When flow lines become visible on a Proof die, the die will normally be repolished.”

 

J. Dannreuther, Official Guide to Coin Grading and Counterfeit Detection, at 10-11 (2d ed. 2004).

 

The sentence "When flow lines become visible on a Proof die, the die will normally be repolished” implies that the wear on a die imparts flow lines that produce luster. But I'm not sure that's what he intends to say, especially because it seems inconsistent with this description of "flat" luster: "flow lines are invisible to the unaided eye, as often happens when coins are struck from worn dies).

[physics-fan3.14]

Thanks Woody and Lou, for posting those here. I wanted to comment, especially on your post Lou, but I'm not a member ATS.

 

Dannreuther does seem to be making contradictory statements, but I think his assertion that flat luster comes from worn dies is the incorrect part. My 1950D shown in the original post definitely qualifies as flat luster, but those dies are not LDS.

 

Look at the progress of a die from prooflike, to semi-pl, to regular strike. The prooflike coin is from fresh new dies - any luster present is due solely to the metal moving. Obviously, there isn't much luster. Its the very act of wearing on the die that eliminates the mirror finish and produces lustrous coins. As the die continues to wear, these etched flowlines get stronger, and each strike makes them stronger. Its a reinforcing cycle. Polishing the dies interrupts this process, which is why coins with strong die polish don't appear to have as strong luster. As the die nears the end of its life, the flowlines become very deeply etched (relatively - they still aren't that big) These larger flowlines produces very coarse luster towards the end of its life, what I would describe as hard luster.

 

At some point over the life of the dies, there is a balance between great luster and die wear, as Woody points out. Depending on what you like, you might call this peak differently than others, but it seems to me this is how the die/luster progresses.

[physics-fan3.14]

Reviewing in preparation for the conclusion to this series, I noticed the pictures were gone from this thread. In recompense, here are a series of coins ranked from best to worst based on their luster: