Milk Spot Mystery Solved
PLE
Posts: 193 ✭✭
Here is my solution to the Milk Spot Mystery:
1. For silver coins, the mint uses a chemical wash, which is probably similar to Acetone. The chemical wash evaporates from the coins. As the chemical evaporates, the coin's temperature is lowered. If the temperature of the coin is lowered below the dew point of the surrounding air, very small amounts of water can condense on the coin. These tiny drops of water start a chemical reaction with the silver. The result is small, invisible "water spots" on some coins.
2. When the coin is encapsulated, the process of sonically sealing the slab can create gasses from the plastic and/or the gasket. These gasses react with the areas of the coin where the condensation previously occurred (the "water spots"). It is possible that the process of sonically sealing the slab also ionizes the water spot areas, which would facilitate the chemical reaction.
In summary, tiny "water spots" are caused by rapid chemical evaporation, and exist on some coins. The encapsulation process turns these tiny water spots into milk spots.
So, based upon this analysis, I can think of only one possible way to avoid milk spots in modern silver coins when they are encapsulated:
Prior to encapsulating the coin, a very brief dip should remove the tiny water spots, and, as a result, prevent the milk spots.
1. For silver coins, the mint uses a chemical wash, which is probably similar to Acetone. The chemical wash evaporates from the coins. As the chemical evaporates, the coin's temperature is lowered. If the temperature of the coin is lowered below the dew point of the surrounding air, very small amounts of water can condense on the coin. These tiny drops of water start a chemical reaction with the silver. The result is small, invisible "water spots" on some coins.
2. When the coin is encapsulated, the process of sonically sealing the slab can create gasses from the plastic and/or the gasket. These gasses react with the areas of the coin where the condensation previously occurred (the "water spots"). It is possible that the process of sonically sealing the slab also ionizes the water spot areas, which would facilitate the chemical reaction.
In summary, tiny "water spots" are caused by rapid chemical evaporation, and exist on some coins. The encapsulation process turns these tiny water spots into milk spots.
So, based upon this analysis, I can think of only one possible way to avoid milk spots in modern silver coins when they are encapsulated:
Prior to encapsulating the coin, a very brief dip should remove the tiny water spots, and, as a result, prevent the milk spots.
0
Comments
a quick dip in what? acetone?
<< <i>interesting hypothesis
a quick dip in what? acetone? >>
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<< <i>
<< <i>interesting hypothesis
a quick dip in what? acetone? >>
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Nah, this is French Onion Dip. The skull and crossbones
is for the way it'll make your breath smell.
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where is it written these are truly sonically sealed instead of "sonically" just being a marketing buzzword? I've cracked a few and the edges seem to be connected at discreet points instead of around the entire edge.
<< <i>interesting hypothesis
a quick dip in what? acetone? >>
No. Ezest.
<< <i>Here is my solution to the Milk Spot Mystery:
1. For silver coins, the mint uses a chemical wash, which is probably similar to Acetone. The chemical wash evaporates from the coins. As the chemical evaporates, the coin's temperature is lowered. If the temperature of the coin is lowered below the dew point of the surrounding air, very small amounts of water can condense on the coin. These tiny drops of water start a chemical reaction with the silver. The result is small, invisible "water spots" on some coins.
2. When the coin is encapsulated, the process of sonically sealing the slab can create gasses from the plastic and/or the gasket. These gasses react with the areas of the coin where the condensation previously occurred (the "water spots"). It is possible that the process of sonically sealing the slab also ionizes the water spot areas, which would facilitate the chemical reaction.
In summary, tiny "water spots" are caused by rapid chemical evaporation, and exist on some coins. The encapsulation process turns these tiny water spots into milk spots.
So, based upon this analysis, I can think of only one possible way to avoid milk spots in modern silver coins when they are encapsulated:
Prior to encapsulating the coin, a very brief dip should remove the tiny water spots, and, as a result, prevent the milk spots. >>
On what basis do you say it is acetone? Another forum member believes that it is butyl cellosolve.
High magnification microscopy indicates that the spots form on the rougher areas of the coin's surface. One spotted coin was examined using a technique known as ESCA or XPS and indicated that only chlorine was present along with of course, silver.
...any idea what they use....?..even a guess would help?
Do a search of past posts....you should find it.
I didn't intend to suggest that the Mint uses acetone. I don't know what the mint uses in its chemical wash. The more important concept that I was trying to suggest was that the evaporation of the chemical wash potentially causes some type of water-spotting.
Something in the environment brings them out.
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<< <i>don't forget to claim your PCGS reward
PCGS did not offer a reward for preventing milk spots but a reward for removing them without damaging the coin.
As for the OP's "solution", its viable and I always use it prior to ANY SAE submission. It should be noted that milk spots are not always the result of slabbing. I've got DANSCO coins which have never seen a slab that are spotted. I've also opened rolls of SAE's that had spots.
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<< <i>....milk spots can happen to raw coins as well.
Something in the environment brings them out. >>
Or it could be just time...
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<< <i>The US Mint does not use acetone or anything similar. >>
....my understanding also.
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<< <i>I always thought milk spots are "in" the surface, not "on" the surface.
Depends on your definition of "in"
<< <i>The information about what the Mint uses along with how the spots might form was passed to PCGS via message to Don Willis. I'm confident they will perform appropriate experiments. >>
So, it's a secret?
I've been told I tolerate fools poorly...that may explain things if I have a problem with you. Current ebay items - Nothing at the moment
<< <i>High magnification microscopy indicates that the spots form on the rougher areas of the coin's surface. One spotted coin was examined using a technique known as ESCA or XPS and indicated that only chlorine was present along with of course, silver. >>
I guess two approaches can be to find out what is causing it and stop it
and
fix the problems that have happened.
Re: fixing the spots
If they only consist of Ag and Cl.... are there any chemists that have been consulted on the possible compounds and the "solution" (pun!) to removing them?
It preferable for PCGS to do their tests with the information provided to them.
<< <i>... very small amounts of water can condense on the coin. These tiny drops of water start a chemical reaction with the silver. >>
I like the theory but have a question. Water condensing out of the air would be of similar purity as distilled water. What kind of chemical reaction would start?
and they're cold.
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<< <i>
<< <i>High magnification microscopy indicates that the spots form on the rougher areas of the coin's surface. One spotted coin was examined using a technique known as ESCA or XPS and indicated that only chlorine was present along with of course, silver. >>
I guess two approaches can be to find out what is causing it and stop it
and
fix the problems that have happened.
Re: fixing the spots
If they only consist of Ag and Cl.... are there any chemists that have been consulted on the possible compounds and the "solution" (pun!) to removing them? >>
Neither cyanide nor thiosulfate will remove them once formed.
<< <i>
<< <i>... very small amounts of water can condense on the coin. These tiny drops of water start a chemical reaction with the silver. >>
I like the theory but have a question. Water condensing out of the air would be of similar purity as distilled water. What kind of chemical reaction would start? >>
None.