milk spots on silver and proofs?

[copperman]

milk spots on silver and proofs? can anyone explain why this can happen, and why it happens ect...

[hoard]

I do not know how it happens but I do know it happens in the manufacturing process of the planchet. The spots are not removable as they are very much part of the coin and embedded in the metal. How the mint is allowing these milk spots to occur on some the ASE I have read about is beyond me. Seem immpausible that quality control is not picking these up. Sorry I do not have a better answer.

[SkyMan]

This seems to fade in and out as a problem. I collect cameo Frankies, and this was a real problem in the late 1950's and early '60's but then seemed to clear up in the latter '60's (I couldn't tell you about any later date proofs as I don't collect them). The most plausible explanation for milk spots of that era (and thus I would assume something similar for today) is that the spotting is due to a residue left from a cleaning solution used on the planchet in its preparation for striking. An Ivory soap bath was frequently used at that time for this purpose, although the mint was constantly experimenting with various other agents.

[TomB]

There has been a longstanding theory that the milk spots or stains that are so common on the 1922 and 1923 Peace dollars are a result of relatively hot Philadelphia summers that required excessive amounts of alcohol cooling agents on the planchets and machinery. I don't know if it has been proven, or if it even could be proved, but it is an interesting thought.

[hoard]

it makes sense Tom, as I thought the milk spots are a result of moisture spots on the planchet during some part of the cooling/drying process. So the theory seems to hold water if they were in fact using excessive alcohol agents in an effort to ensure the elimination of moisture in the manufacturing process.

[zrlevin]

it makes sense Tom, as I thought the milk spots are a result of moisture spots on the planchet during some part of the cooling/drying process. So the theory seems to hold water if they were in fact using excessive alcohol agents in an effort to ensure the elimination of moisture in the manufacturing process.

 

"Hold water"...ha ha...get it?

 

Oh nevermind...

[copperman]

it makes sense Tom, as I thought the milk spots are a result of moisture spots on the planchet during some part of the cooling/drying process. So the theory seems to hold water if they were in fact using excessive alcohol agents in an effort to ensure the elimination of moisture in the manufacturing process.

 

"Hold water"...ha ha...get it?

 

Oh nevermind...

[hoard]

I was in fact trying to be funny. Sometimes it works sometimes it does not.

[just-john]

I have run a metal press's and CNC machinesThe spots milk spots look like there left on after the the planchet come out of the die which is lubed fine spray of coolant/lube and not cleaned very well after the strike.The lube is non flamible water base many different kinds.

If tey were to change to a bicarbonate and liquid carbondioxde system the milk spots would be gone.I think there running the presses to fast with all the products the mint coming out with and this is the result.You can have it fast or you can have it right Their thinking fast

[physics-fan3.14]

if they were in fact using excessive alcohol

 

Not the best way to be productive. Opens up a whole new possibility of what those spots are...

[just-john]

There coolant or lube for sure

[just-john]

If you are near a machine shop cnc lathe press or metal band saw take a look ask them what they use to coolthere mill ends or blades.When sombody does they see the same liquid

[DC Dawg]

milk spots on silver and proofs? can anyone explain why this can happen, and why it happens ect...

Planchets are washed before minting and the coins are washed after. Since proofs are struck 2-3 times and increases the temperature significantly, I suspect that these spots are from the post striking wash that wasn't properly rinsed and put into holders before they completely dry.

 

Scott

[hoard]

guys we are definately narrowing it down to something that happens during the planchet production process, and has to do with some water based lubricant or washing solution. This is good enough for me.