How Does the Mint BURNISH Silver Eagle Blanks and Can They be ID'd Post-Strike?

Akbeez

I looked back in the forums on this question and there are at least three answers found: water blasting, tumbling, and rubbing the planchets (blanks) were answers given.

Has there been an answer given from the Mint on the exact procedure? If known, please indicate your source.

Second question is: Can a burnished blank coin be identified from a non-burnished blank post-strike?


*Edited Post Title

Crocidile65

"18th Century Burnishing

Burnished coins available in the 18th century were specifically minted for the purpose of creating proofs or special editions. The process of burnishing occurred before the planchet was struck during the minting process. The burnishing process in the 18th century utilized wet sand to polish the planchet to a high gloss. Burnished coins, once struck, had a significantly higher shine in areas not directly affected during the striking process.

Restorative Burnishing

Restorative burnishing is typically considered a nondesirable restorative method. A variety of methods are used to remove the patina. Surface scratches actually remove some of the original metal during the process. High-speed drills and buffing pads are commonly used to create a high shine or luster on coins. Burnished coins are considered restored coins and are not as highly graded as original burnishing.

Modern Burnishing

Modern burnishing processes, like during the 18th century, are performed on the planchets prior to the strike process. Machine buffing of the blanks yields mirror-like surfaces for striking proof and special-editions coins.

As an example, American Eagle proof coins are produced using a burnished blank that is manually fed into the striking machine by handlers using white gloves to avoid marring the surface with oils from the skin. The coin is struck multiple times. According to the U.S. Mint, this process yields a coin that is "softly frosted, yet detailed images seem to float above a mirror-like field."


Read more: What Is Burnished Coin? | eHow.com http://www.ehow.com/info_7825651_burnished-coin.html#ixzz1fqIya3w2

References

United States Mint: American Eagles
Professional Coin Grading Service: Lingo - The Language of Coin Collectors"

jmski52

When the debate about burnishing of the Goodacre Sacs was ongoing, it came to light that the Mint had tried several different burnishing compounds and had experimented with various burnishing sequences.

They started burnishing the Silver Eagles in '06, so I would expect that their process is thoroughly standardized by now, and I doubt that they are willing to let too many people in on their secrets.

When I saw the results from a tumbler and treated corncobs on brass casings at a gun show a couple years ago, I was quite amazed at the job they could do.

Gemineye

Perhaps a simple method of explaining what burnishing is ..is that the metal or blanks are placed into a vibrating cylinder or holder with other media.The vibrating cleans and polishes the metal or blanks.In the case of the Sacagawea Dollars..corn cobs were added for color....

FredWeinberg

When I last visited the West Poin Mint
in 2006, I saw the entire operation for
for Gold and Silver Eagles, and was
actually allowed to strike a Proof Silver
Eagle - using white gloves, a pair of
plastic prongs to place the Planchet
into the striking press/collar, and press
the button to strike it.

I have photos of me doing this - but I
can't locate the original photos to
post (I have copies in my supply case
that I'll be glad to show at FUN).

To answer the OP question - the planchets
are placed in a large circular 'washing machine'
with huge amounts of small plastic pellets;
the planchets are then 'spun' around, to
burnish them.

They then get a wash, and are dried flat,
in trays - then moved to the Press Room
to be struck as Proofs.

I've always thought that the water spots
that are on the ASE's, especially some years,
are due to either a dirty, unchanged batch
of water, and/or improper drying......

By the way, I have photos of various sizes
of Gold and Platinum Eagles, sealed in
plastic sheets, labeled by the Mint as
"First Strikes"...!


Fred

Coins101

Interesting. You would think they would have labeled them "Struck First."

19Lyds

<< <i>Perhaps a simple method of explaining what burnishing is ..is that the metal or blanks are placed into a vibrating cylinder or holder with other media.The vibrating cleans and polishes the metal or blanks.In the case of the Sacagawea Dollars..corn cobs were added for color.... >>

I thought that the Sacagawea's were burnished "after" the minting process which is the primary reason the ICG did not assign a grade to the Goodacre Sac's?

Or am I getting confused again?

Akbeez

<< <i>To answer the OP question - the planchets
are placed in a large circular 'washing machine'
with huge amounts of small plastic pellets;
the planchets are then 'spun' around, to
burnish them.

They then get a wash, and are dried flat,
in trays - then moved to the Press Room
to be struck as Proofs.
Fred >>



Thanks Fred (and others) -- I didn't realize the proof blanks were burnished also.

Since the blanks for the burnished unc silver eagles are specially treated this way (essentially textured), is there not a way to "detect" this treatment under magnification as compared to non-burnished?

dac076

To answer the OP question - the planchets
are placed in a large circular 'washing machine'
with huge amounts of small plastic pellets;
the planchets are then 'spun' around, to
burnish them.

Thanks Fred. It sounds like you are describing a tumbling process. It's often used in metal fabrication to remove burrs from parts.
Different tumbling media are used depending upon the material and the desired finish.

leothelyon

Now that we know the US Mint has coins that will make the stuff we play with look like crap.......what else is on the agenda?





grammar error

IrishMikey

<< <i>

<< <i>Perhaps a simple method of explaining what burnishing is ..is that the metal or blanks are placed into a vibrating cylinder or holder with other media.The vibrating cleans and polishes the metal or blanks.In the case of the Sacagawea Dollars..corn cobs were added for color.... >>

I thought that the Sacagawea's were burnished "after" the minting process which is the primary reason the ICG did not assign a grade to the Goodacre Sac's?

Or am I getting confused again? >>


That was ICG's original theory to account for their unusual appearance and surfaces. It was later established
that all of the work done at the Mint was "Pre-Strike" burnishing of the blanks, and special treatment of the
dies -- nothing was "Post-Strike." There was a thorough discussion of the entire process published in Coin
World, sometime around 2003, I think.

Gemineye

<< <i>

<< <i>

<< <i>Perhaps a simple method of explaining what burnishing is ..is that the metal or blanks are placed into a vibrating cylinder or holder with other media.The vibrating cleans and polishes the metal or blanks.In the case of the Sacagawea Dollars..corn cobs were added for color.... >>

I thought that the Sacagawea's were burnished "after" the minting process which is the primary reason the ICG did not assign a grade to the Goodacre Sac's?

Or am I getting confused again? >>


That was ICG's original theory to account for their unusual appearance and surfaces. It was later established
that all of the work done at the Mint was "Pre-Strike" burnishing of the blanks, and special treatment of the
dies -- nothing was "Post-Strike." There was a thorough discussion of the entire process published in Coin
World, sometime around 2003, I think. >>



I tried to save the links from Coin World..but aparantly I can't access them.The year that the issue was discussed is 2001 though,,if you can reserch their archives..
....news/032601/news/.........04210........and 061801.......

Akbeez

thoughts from the evening crowd...?

Ejoty

If there is an interest, I could get a quote from our nanotech lab at work. They should be able to determine any differences in structure or chemical makeup of sample coins in a couple of hours. PM me if you have a serious interest.

Akbeez

ejoty, thanks for the offer. Before we start a contractual investigation, I would hope there would be a numis-geek (respectfully) out there techno-savvy and interested enough to answer the question. The person would need a solid understanding of the dynamics of metal flow under pressure as it applies to coinage processes, etc.

How a non-burnished blank could end up with a post-struck textured finish is the question. That is, unless the die was treated for that effect...

Akbeez

For the weekend gang. Any metallurgist/numismatists out there?

Akbeez

TTT

Akbeez

Any experts out there?

SUMORADA

No expert here but in the Jewelry Biz there are Magnetic Finishing Machines that Burnish whatever ............these machines work by rotating small steel needles in a circular pattern.....see link.

link

edited to add......I have one of these machines, when I said...............these machines work by rotating small steel needles in a circular pattern

I may have understated what they do.......when running the create a tornado like effect ....very efficient.