Anyone seen milk spots / stains on Kookaburras ?

P

Photonaware

Active Member
I thought the problem with milk spots and stains, that cannot or are extremely difficult to remove, on silver coins was exclusively a quality problem at the Royal Canadian Mint with their Maples and similar bullion coins.
Possibly caused by baked on chemicals or detergents that clean the presses.
There have been lots of threads on this topic and many stackers shy away from RCM because it is quite common.
I have seen these spots and blemishes on many brand new Maples and they are distracting and ugly.

However I have yet to see such stains on Perth Mint products.
Until today that is -

Here is a photograph showing major spots and a large milky-like area, which extends across the frosted area as well, on a 1 oz 1999 Kookaburra.

731_img_2084.jpg


Has anyone seen this problem on Kooks before ?
 
I receivd a 2012 chinese panda still inside the original mint capsule that had a couple noticeable milkspots on it... it doesn't happen very often (except for canadian coins obviously) but it does happen...

The dealer I purchased from was more than happy to exchange it for a new BU panda, so no harm done.
 
I know a Kilo Kooka in it capsule that has a small milk spot - but it does not look like the one you posted (it's round and looks somehow more "sharp" or "cristallite" - looks like it could be a drop of dried salt water (not suggesting that it is one ;))).

The picture indeed looks kinda ugly. How did you store it? Or did you buy it in this condition?
 
You just made me re-check all my coins lol.
No milk spots on any of my kooks or maple leafs.
 
Rare on PM bullion items but agree its only uncommon on older proof PM stuff.. the velvet/plastic casing?

Philharmoniks get them hardcore, as do NZ 9999 fine Silver Ferns (even sealed )

1for1
 
Just in case anyone asks it was purchased that way from a very reputable dealer. Arrived the day of this post and took photo. Obviously hoping to get it swapped but first time for a Perth Mint coin. Definitely similar to bad stains & spots on Maples and not something that rinses off. Many thanks to all who have shared their experiences. Just unlucky I guess but must have slipped the QC in the Mint 12 years ago.
 
Considering how common milk stains are, has anyone determined just what causes them? I've heard theories but nothing saying that the cause has definitely been identified.

Just a few years ago I had seen or heard of the stains as occurring only with Canadian Maples but now......
 
WTF?
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TomD said:
Considering how common milk stains are, has anyone determined just what causes them? I've heard theories but nothing saying that the cause has definitely been identified.

Just a few years ago I had seen or heard of the stains as occurring only with Canadian Maples but now......
Click to expand...

3rd try...

I have seen milk spots on American Silver Eagles, Australian Perth Mint 2012 Dragons, Canadian Silver Maple Leaf & especially bad on Canadian Wildlife Series. I think all mints getting in a hurry with too many orders. My research on milk spots seems to indicate not so much a purification issue but a processing issue with the silver planchets (rounds). The rinse/cleaning process can leave a silver chloride(1.) (chlorine) based residue. "The problem may be using recycled water when rinsing the blanks, eventually the water used may be contaminated enough to not do the job it was suppose to do. The chlorine residue reacts with "fresh" air becoming progressively worse once exposed." (2.)

1. http://en.wikipedia.org/wiki/Silver_chloride

2. http://china-mint.info/forum/index.php?topic=3497.0;all

" Seen on silver coins, milk spots are created from chemicals used in the manufacture of the planchet before being struck into the finished coin. This struck in nature makes them impossible to safely remove through conservation." (3.)

3. http://boards.collectors-society.com/ubbthreads.php?ubb=showflat&Number=3990846#Post3990846

"I suspect that the spots are silver chloride. The silver comes from the coin, and the chlorine comes from some chemical like an acid - probably something like an HCl (hydrochloric acid) pickling solution for cleaning the planchets prior to striking.

When the chemical dries, it becomes mostly unreactive. When the chemical is exposed to humidity in the air, it can pull water (H2O) from the humidity in the air. The H in the H2O combines with the Cl in HCl to create hydrochloric acid that reacts with (dissolves) the silver to create silver chloride.

Once this damage is done, it cannot be undone by conservation because it's far more aggressive than a normal toning reaction, and digs down into the metal instead of just staying on top of the metal where it could be removed.

Conservation would probably remove most or all of the Cl before it had enough time to absorb H from the air - and that would prevent the reaction from occurring before it starts." (4.)

4. http://china-mint.info/forum/index....b44b1f3d5e2cd0609e&topic=2300.msg7969#msg7969
 
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