This is the crux of the issue and unfortunately we don't have a definitive reason, otherwise we would have made a statement and said all our coins will never have a problem. This old statement is the best we have at this moment http://forums.silverstackers.com/message-754761.html#p754761 I know this isn't what you are looking for but there hasn't been any advance since then.
I'm be happy to put money that it's the solution. Spots are where the solution has dried and over time time this is the spot. Chemical analysis of the solution would show the -Cl component in it. The rest is elementary dear Watson.
Could the problem with the chemicals be compounded by the change in the manufacturing process that results in a rougher surface finish? "The change of minting process of forming mirror surface has caused more and quicker white spots formation. The old method in produce mirror surface was mechanical polish. The current method is via a chemical treatment. Apparently, according to the authors, the chemical treatment produces a rougher surface than mechanical polish. It is known that the moisture can adhere to a rougher surface better than a smooth surface, therefore, the reaction of forming silver chloride film on the silver surface is being accelerated."
Do proof coins get different treatment from normal bullion coins? If it was debris it would be found across the whole range of products. The same goes for crucible materials. If it is the cleaning solutions then do they differ between proof and bullion products? When I first heard about the issues they were confined to pretty much one Mint, The Royal Canadian Mint, and one product line, the Bullion Maples. Now it seems to be all over the place and across many of the product lines. Do milk spots appear on bars? If they do then it isn't much use but if they don't, and I haven't seen any, then this might rule out certain causes.
Yes. Usually the minted ones when it does happen, but I even have a cast bar that's got milk-splotches.
Not from the surface finish. It's from the solution used. I'd be 10000% sure all manufacturers know this. But they are heavily invested in the process and do not want to change. That's why they say "we don't know". It's the solution. Impurities don't milk spot.
Thats right, impurities start out as a tiny spec or dot that changes color to like a black or brown or whatever and then the stain from the impurity spreads out from the spot/spec etc , this is not the same as milk spots.
Exactly. It's actually really obvious. And it's is really super annoying the response from the mints. They KNOW, it doesn't even take a chemist to figure this out, the treated chemical has -cl component. It's the only way! Basic deduction and high school chemistry would suffice. To me the mints would have investigated this a long time ago and are in all probability deceptive with intent and deserve a savage backlash. I dislike lies. Places like PERTH MINT should make a statement detail the issue and cause, issue an apology and be rushing to fix the problem instead of continuing to prevaricate.
Maybe the mints would rather us stick with poured bars from elsewhere, instead? How about throwing in some really old un-spotted numi's, as well? Plenty of places to spend that limited budget..
So i read the original thread and it is 8 months on, how has their new process and quarantined coins go?
Yes from your armchair it is really very obvious. Do you really think that we don't want to fix this problem? The first mint that can make a guarantee of no milkspots would gain a significant sales advantage. But no, we are so "invested" in our processes that we don't want to change - what does that mean? Our technical staff are not in love with our processes, they are constantly changing them and adjusting them to lower cost and improve quality. We spend tens of millions investigating and buying new machines - it is constant change in the factory. I get your frustration and our guys feel the same but at this time they don't have a definative answer beyond semi-conductor style clean rooms which would push the cost so high that we wouldn't sell anything.
Sorry Bron, Though I am going to have to take exception to this one. I do appreciate your time and answer so don't get me wrong, it's a major issue. Also if you want my participation I'd be more than happy to help and get you a definative answer. I live in Sydney though. Firstly milking didn't happen on previous coins. It is a new phenomena. Particulates would be an unlikely cause. Here's an article by coinweek. http://www.coinweek.com/education/c...s-crying-milk-spotted-american-silver-eagles/ Now I recommend the genius non armchairs over at the Perth Mint fix the issue. It's clear what it is. I did the google just now and found enough info on it. And if you guys really don't know what's causing it for this LONG amount of time then people deserve not to have their jobs and I mean that. Hire people who are competent. Delivering a product like that is so unfair to customers, i don't think there's a leg to stand on. The premiums relative to other much cheaper rounds (that don't milk spot) should mean a better product. Bron, we are not just disappointed, we are fuming. We all bought product that we "collect" and "invest" in with the hopes of greater it appreciating and then we get hit with milk spots. Shoulder shrugging is just abysmal. I still find it impossible to believe you guys haven't figured it out, just impossible and you won't be able to convince me otherwise lest for incompetence. Harsh but deserved IMO. Also this is directed at Perth Mint not you personally, I like you BTW and thank you for your time.
^ Though the article focuses mainly on ASE's, it describes the very bad feelings collectors are increasingly having for the milk spot problem on coins from other mints including the Perth Mint. .
One more thing Bron... The armchair comment got to me. Here's Curtin Uni over in Perth... plenty of metallurgy folk on staff. http://mining.curtin.edu.au/people/ I've looked at their bio's, they would be a good point of call initially for you guys. If you have no joy, let me know. Happy to make a few calls, my family has a few professors and my uncle is a Emeritus Prof from UNSW. Not all of us have the IQ of nats just cause it's "the internets". Also if you do follow through and are sincere, get a public statement out with what you find and what's being done about it. Am just sitting in my armchair at the moment watching Idiocracy.
I think what we have is that all these mints do know how to fix the problem "but" the cost would go up , so as long as the rest of the mints are doing it the cheap/ milkspot way then any one mint will not change unless they find a way to do it as cheap as the current cheap/milkspotty way. Or all the other mints start doing it the expensive way that eliminates the milkspots which I don't see happening. So it appears we are stuck with milkspots unless someone can find a cheap "solution" ..... pun there I think, or not. :/ I was referring to bullion coins, not proof high premium collector coins, There is no good excuse to have milk spotting on these type of coins, if these high value proofs etc are getting milk spots then we know the mint cheaped out on somewhere through the process on making these coins. Shame on them...
Did all the mints during the 1970's shut down their clean-rooms prior to the milk-spot boom? And would love to see photos of clean-rooms at the mints during the 1870's. My theory? In their quest for "the perfect strike," at some point many mints started experimenting with different (chemical?) processes in order to hit that level on a consistent-enough basis. And in doing so, inadvertently opened a whole new can of worms, i.e., the dreaded milk-spot. Now they're stuck between a rock and a hard place. On some levels, it's almost as if decades of minting advances have been for naught. Of course, the first mint to come forward & publicly claim that their coins won't milk-spot will certainly have bragging rights & become the envy of other mints -- who will then scramble in order to be able to claim the same. Until then? Same old, same old. Spend wisely..
Do you think we just happen to have some scanning electron microscopy thingamajgies lying around http://forums.silverstackers.com/to...electron-microscope-images-of-white-spot.html
No problem, this is obviously an area I don't have any technical expertise in or authority over and just passing on info. And I'm sure my comments were too blunt to win any social media awards for the correct way to "engage" with customers. We are all big boys and girls here.
bron any chance you can comment on what happened to the testing that was conducted by perth mint back in Jan? Has the removal of particles assisted with less milk spots?
