Has anyone seen the reports on the efforts of the US Mint to solve milk spots?
Herb_T
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I am looking for any reports, detailed analysis type, on the problem of milk spots produced by the Mint itself. Anyone ever see any of these?
I have a FOIA request into the Treasury Department now, but would like to see any reports that anyone has so I can be sure I use the same terms for the problem that they do.
Anyone?
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https://forums.collectors.com/search?Search=milk+spots
I have done a search and have come up with similar information from the forum. What I haven’t found were the detailed reports from the Mint on their investigations. I want these reports to see how far they went into this. I am an engineer and have had to solve process problems like this. By seeing what they have done, I can see where there may be gaps. I have connections with some universities and labs that can also help to dig into this. This can be solved…..just have to find the right road that will lead to a solution.
Not exactly what you asked for, but very much related https://www.researchgate.net/publication/263222095_Nanotribology_Application_in_the_Coining_Industry_I-Turn_off_Stamping_Oil_Sprayer_during_Coining
It goes into great depth about all the different chemicals that planchets and coins are subjected to and the resulting surface effects such as spotting, tarnish, resistance to spotting and tarnish etc...
Mr_Spud
That is worth a read….thank you!
Years ago with the assistance of one of the scientists at the Ames Lab, U. S. Dept of Energy we did an analysis of the spotting on a silver eagle [the spotting looked a lot like bird droppings on the hood of your car] using a technique called ESCA or XPS x-ray photoelectron spectroscopy. The only element present besides silver was chloride.
Also at one time I was in contact with the head of QC for the U. S. Mint and she indicated that they were looking into the problem. They were going to purchase a mass spectrometer [for what reason I do not know] but due to sequestering the purchase was on hold. Some time after that she moved on to the BEP.
In one of the more recent videos of the striking of ASEs at the mint they show a worker oiling the edges of a stack of planchets before being placed into the press. They don't show anything about how the oil is removed.
Also from the linked reference.
"Pick-ling compounds are added into the rotating barrel to remove themetal oxide layer generated during annealing. After rinsing,"
A common pickling agent would be hydrochloric acid and we already know that this was being used to wash planchets back around the time that the Peace Dollars and 1921 Morgans were being struck.
The mint has worked with NIST on die lubricants.
Perhaps the two have or could work together again.
It’s be interesting to see their receptiveness of outside research orgs.
The RCM seems to have a solution. I dont know what it is.
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Interesting. Thanks for posting about this.
Reference Article #1: 'Generic/marketing' overview of "MINTSHIELD" from the RCM website. No real 'specifics/details'.
Reference Article #2: An RCM update from one year after introduction. Highlights:
~ " [...] there have been no reports of white spotting on the first generation of SML coins protected by Mintshield" [from customers].
~ an independent lab subjected 2018 SML coins, treated with MINTSHIELD, to accelerated aging testing (i.e., a hot and humid environment designed to simulate an extended period of time in a short time frame). "The Silver Maple Leaf [...] showed no signs of white spots on the obverse or reverse".
Seems like RCM has solved it. Not sure if they're willing to share their findings with other mints.