Featured Luster: A guide for Beginners

vrt · Jun 28, 2009

What is coin luster

I remember how the idea of luster was confusing to me couple years back. physics-fan3.14's and GDJMSP's posts are really useful and not just for beginners. GDJMSP's explanaition of how metal flows reminded me that my major was physics and now I have to ask a stupid question - What is the luster? I see 2 options here.

1. luster is the specific difusion of light. This option is supported by the mint's definition: "the dull, frosty, or satiny shine found on uncirculated coins". Discussion of different types of luster also based on this definition. This option has a dangerous effect - if your coin is locked in a safe you cannot say it has any luster - there is no light difusion without the light.

2. luster is the irregularities on the coin serface that cause the specific difusion of light. I have to go with this option (as a phisysist and as a collector who would not except the idea that his/her coins lose their luster at night). In this case the luster is not "shine" or "light difusion" - then it is hard to say that luster can be "booming" or "dull", right?

Thank you.

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GDJMSP · Jun 28, 2009

physics-fan3.14 said: ↑

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.
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Don't get mixed up here now. That is what I and Dannreuther was trying to explain. It is not that luster gets stronger with die wear - it merely changes from one type of luster to a different type of luster. A luster with a different look.

If one truly wanted to quantify luster, meaning actually measure which luster was stonger than the rest, it would be Proofs, Proof Like coins and EDS business strikes that would have the strongest luster, in that order. This is because what you would be measuring is the actual amount of light that is reflected by a given surface. You would obtain that by firts measuring the strength of the light from the source and then measuring the strength of the light being reflected from the coin and subtracting the difference.

In every case, the closer the surface of the coin was to a mirror, the stronger the reflected light would be. This is common sense, but it can be proved.

So keep in mind, it is not that luster gets stronger as the die is used - it's that the look of the luster changes. That's all. Semantics maybe, but accurate.

physics-fan3.14 · Jun 28, 2009

GDJMSP said: ↑

Don't get mixed up here now. That is what I and Dannreuther was trying to explain. It is not that luster gets stronger with die wear - it merely changes from one type of luster to a different type of luster. A luster with a different look.
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Agreed.

Thanks for all your additions to this thread, Doug.

physics-fan3.14 · Jun 29, 2009

Thanks for the Thread of the Week award, guys.

physics-fan3.14 · Dec 24, 2009

As the subjects of toning and luster are intertwined, the topic of Luster has been coming up with some frequency in my What You need to Know About the Science of Toning thread, here: http://www.cointalk.com/t84670/

So, I thought I would bump this up for you guys.

GDJMSP · Dec 25, 2009

If I had to choose 5 of the most important threads that have ever been written on this forum - this would be one of them.

chip · Dec 27, 2009

this post that I just reread has a great question in it

vrt said: ↑

I remember how the idea of luster was confusing to me couple years back. physics-fan3.14's and GDJMSP's posts are really useful and not just for beginners. GDJMSP's explanaition of how metal flows reminded me that my major was physics and now I have to ask a stupid question - What is the luster? I see 2 options here.

1. luster is the specific difusion of light. This option is supported by the mint's definition: "the dull, frosty, or satiny shine found on uncirculated coins". Discussion of different types of luster also based on this definition. This option has a dangerous effect - if your coin is locked in a safe you cannot say it has any luster - there is no light difusion without the light.

2. luster is the irregularities on the coin serface that cause the specific difusion of light. I have to go with this option (as a phisysist and as a collector who would not except the idea that his/her coins lose their luster at night). In this case the luster is not "shine" or "light difusion" - then it is hard to say that luster can be "booming" or "dull", right?

Thank you.
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sort of the classic question if a tree falls in the forest...

physics-fan3.14 · Jan 19, 2011

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, similar to the progression of Jeffersons Lehigh posted:

ldhair · Jun 22, 2014

Great choice for a featured thread.

definer · Jun 24, 2014

Can someone provide a definition of EDS, LDS, and MDS?

Thanks!

geekpryde · Jun 24, 2014

definer said: ↑

Can someone provide a definition of EDS, LDS, and MDS?

Thanks!
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EDS - Early Die State
MDS - Mid Die State
LDS - Late Die Dtate
VEDS - Very Early Die State

definer · Jun 24, 2014

Thanks!

torontokuba · Jan 7, 2015

physics-fan3.14 said: ↑

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.
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physics-fan3.14 said: ↑

Its hard to describe, but I might almost call it coarser - which would make sense given the larger size of the flow lines etched into the die repeatedly.
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With my limited magnification, it just looks like frost, so, I started explaining it as frost, to those that clean coins, in an attempt to explain what they were stripping the coin of. My favorite images to use as part of this explanantion, look like this...

If you scratch a smiley into the coin surface, it's permanent.

Swiss Frank images courtesey of @bkozak33

pratik · Mar 15, 2015

How to have a white luster to circulated coins using chemical anyone having idea pls share

GoldFinger1969 · Mar 16, 2015

Fascinating post.....awesome !

Cheech9712 · May 8, 2019

xtrmbrdr said: ↑

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?
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Like that cent icon of yours. What date is it?

Cheech9712 · May 8, 2019

physics-fan3.14 said: ↑

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.

View attachment 630572
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.

View attachment 630573
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.

View attachment 630574

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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Still way over my head

Razz · May 9, 2019

Cheech9712 said: ↑

Like that cent icon of yours. What date is it?
Click to expand...

He hasn't been seen in almost 10 years...

Insider · May 11, 2019

Nice discussion. Unfortunately, I was not a CT member when it first appeared in 2009 as I would have added a few comments.

vrt, asked: "What is coin luster?" He saw two options:

1. Luster is the specific diffusion of light. This option is supported by the mint's definition: "the dull, frosty, or satiny shine found on uncirculated coins." Discussion of different types of luster also based on this definition. PERIOD!

Additionally: In virtually every definition of luster, the reflection of light from an object's surface is what causes the luster.

THE CONDITION OF THAT SURFACE will both modify and determine the QUALITY OF THE LUSTER we observe reflected from that surface.

While this statement is true: "This option has a dangerous effect - if your coin is locked in a safe you cannot say it has any luster - there is no light diffusion without the light." It is unnecessary as there is NO LIGHT involved - the "thing" necessary to bring out the luster. This is also t

2. luster is the irregularities on the coin surface that cause the specific diffusion of light. NO! Luster is the specific quality of the reflected light FROM the coin's surface! The rest of this member's post is more of his thoughtful opinion, Hopefully, he will change it so I'm deleting it from my comments.

GoldFinger1969 · May 17, 2022

So, PF is saying that luster is caused by changes in the die's crystalline structure as it applies 100-120 tons of pressure to the planchets, do I have that right ?

And technically, a proof coin does NOT have luster -- even though it is super-reflective ?

I'm going by the chapter on LUSTER from RWB's Saint-Gaudens DE book. Maybe luster on other coins is different than for gold coins in general and Saints in particular.

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Featured Luster: A guide for Beginners

vrt Junior Member

Guest User Guest

GDJMSP Numismatist Moderator

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

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

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

GDJMSP Numismatist Moderator

chip Novice collector

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

ldhair Clean Supporter

definer definitely....! LOL

geekpryde Husband and Father Moderator

definer definitely....! LOL

torontokuba Thread Crapper & Hijacker, TP please.

pratik New Member

GoldFinger1969 Well-Known Member

Cheech9712 Every thing is a guess

Cheech9712 Every thing is a guess

Razz Critical Thinker

Insider Talent on loan from...

GoldFinger1969 Well-Known Member

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Featured Luster: A guide for Beginners

vrt Junior Member

Guest User Guest

GDJMSP Numismatist Moderator

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

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

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

GDJMSP Numismatist Moderator

chip Novice collector

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

ldhair Clean Supporter

definer definitely....! LOL

geekpryde Husband and Father Moderator

definer definitely....! LOL

torontokuba Thread Crapper & Hijacker, TP please.

pratik New Member

GoldFinger1969 Well-Known Member

Cheech9712 Every thing is a guess

Cheech9712 Every thing is a guess

Razz Critical Thinker

Insider Talent on loan from...

GoldFinger1969 Well-Known Member

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