Featured Luster: A guide for Beginners

YES & No. Luster is the reflection of light from a surface and depending on the surface, angle, and intensity of the light it changes. Original Mint luster has several specific looks based on the way it reflects light, the way it was struck, the condition and composition of the planchet and the condition of the dies. Therefore Proofs are subject to the same things.

What page of the book so I can read it. You see, some folks think the word "luster" only apples to frosty coins rather than the quality of the reflection.

 

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Insider, Page 633 of the Saints DE book.

There's also a good mini-section on Copper and Red Spots right after.

 

Nice thread resurrection. But where is @physics-fan3.14? Haven't heard from him in a long time? Also, where's Waldo?

 

The U.S. Mint:
"Mint Luster: The dull, frosty or satiny shine found on uncirculated coins."

TPGs have taken some liberty in using the term "luster", in my opinion, and have applied the word 'luster" as a description of "Mint Luster", and collectors and dealers follow suit, and it has become a bastardized monetary weapon when describing a coin, and the practitioners seem to forget the word "uncirculated".

How many times have anyone on CT seen or read a description of a circulated coin as: "...some original luster..." or "...still has some original luster with only a slight rub..." (read that one on a 45 Graded piece) or "...mint luster remaining in the majority of fields..."? Anyone on CT, that is how many.

Talk about word appropriation for economic gain....

Et Tu, Insider?

Truth in editing" added a quotation mark.

 

@Insider has it right. Luster is the effect of light reacting with irregularities on the coin's surface. That produces a "cartwheel" effect. It's why later-stage, worn dies, often have booming luster. It's due to the irregular, "wrinkled" surfaces on those dies, while other areas of the same dies may be PL, or "mirror" finish. You need to have irregularities for luster. That's why when a coin is rubbed and the mint flow lines are disturbed, the luster goes.

 

From the Saint-Gaudens Double Eagle book (and this might ONLY apply to Saints, not saying it applies to other coins from that era or coins struck decades later):

"Luster......is the visual result of light reflecting off of thousands of tiny ridges and grooves of metal in the smooth (field) areas of a coin. These imperfections were created in a working die as the hard steel was stressed during the striking of thousands of blank planchets.

The original surface of a coinage die is smooth....and largely free of imperfections.....The pressure, or force, applied to the planchet was approximately 100-120 tons per square inch.....with each blow of the die, an imperceptible movement occured in the crystals of the die face.

Following several hundred strikes, the die face had distored slightly so that the fields were no longer completely smooth, but consisted of miscroscopic ridges and grooves.

This type of surface alteration was most prominent in the fields of a die where movement of the metal was greatest and least inhibited by details of the design. The portrait, inscriptions, and other design elements were sujbect to similar die deformation, but at a much lower rate and magnitude. This explains why a coin shows luster in the fields but not in the raised areas."

 

While I take it that's RWB's explanation on the formation of the lines, I think he's conceding, it's those lines that cause the luster. It's those superficial disturbances, principally in the fields.

 

I'd like to hear Insiders's view on my Saints luster quote above...and GD's and others focus on "metal flow."

They could be 2 sides of the same coin or just overlap. It's above my pay grade.

 

Go back in the threads. Doug had a lot to say on Mint flow lines. Opened my eyes up, anyway, starting with why we don't clean coins. You just don't get those things back.

 

I skimmed it, will re-read it, thanks Eddie.

It was somewhat complicated, at least to this novice.

 

Dang, gotta go back and read through this...

 

Roger wrote nothing about the luster of Proofs on that page.

 

Well, it's from his book so I assume he agrees with it. No reason not to.

Insider, do you agree in whole or in part with what I quoted in Post #66 ?

 

Luster, when applied to coins, is different than when used in other contexts. AFAIK, the coin luster referred to is cartwheel luster. In chemistry, luster simply means shininess or reflectivity. What causes it is an interesting question...

 

Again, Roger did not comment on Proof luster in his quote as you accidentally or incorrectly implied with this post and its source:

"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."

Now that's settled right?

Next, I've already posted my thoughts on "luster." Let's see if I can answer your specific question about Roger's thoughts.

GoldFinger1969, posted: "]From the Saint-Gaudens Double Eagle book (and this might ONLY apply to Saints, not saying it applies to other coins from that era or coins struck decades later):

[Mint]"Luster......is the visual result of light reflecting off of thousands of tiny ridges and grooves of metal in the smooth (field) areas of a coin. [Mint luster of some kind occurs on ALL areas of the coin including the rim] These imperfections were created in a working die as the hard steel was stressed during the striking of thousands of blank planchets.

The original surface of a coinage die is smooth....and largely free of imperfections.....The pressure, or force, applied to the planchet was approximately 100-120 tons per square inch.....with each blow of the die, an imperceptible movement occured in the crystals of the die face.

Following several hundred strikes, the die face had distored slightly so that the fields were no longer completely smooth, but consisted of miscroscopic ridges and grooves.

This type of surface alteration was most prominent in the fields of a die [especially near the rim]where movement of the metal was greatest and least inhibited by details of the design. The portrait, inscriptions, and other design elements were sujbect to similar die deformation, but at a much lower rate and magnitude. [Yes!] This explains why a coin shows luster in the fields but not in the raised areas." [This is not correct. Probably a result of Roger trying to keep things simple. Luster is on all parts of the coin where its surface is still original.

 

He says later on (I truncated the section) that you see SOME luster on the devices but not as much on the fields.

Remember, the section on luster might be specific to Saints ONLY. You were dealing with a 90/10 gold/copper planchett....super-powerful presses....reinforced dies......etc.

 

GoldFinger1969, posted: "He says later on (I truncated the section) that you see SOME luster on the devices but not as much on the fields. [This is correct, did I just imagine I commented on that?]

Remember, the section on luster might be specific to Saints ONLY. You were dealing with a 90/10 gold/copper planchett....super-powerful presses....reinforced dies......etc."

You are frustrating the heck out of me. Please read my comments [between the lines] in your post. I cannot make it any clearer.

What Roger wrote and you quoted APPLIES TO DIE STRUCK COINS. That includes Saints. AFAIK, ALL surfaces except Black Holes reflect some form of light. Now, I hope some very educated weasel can come up with a surface that does not reflect anything just to prove I'm not 100% correct (they must exist) and we all will become more knowledgeable!

 

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lol

 

On the Saint then you say the field is shiny but the lady and torch have luster?