Graded silver milk spot question

[Guybrush]

Hi All,

I dont have any graded silver coins but I am researching them because I want to pick a few up.  My question is for fellow collectors who already have graded silver coins.

Is there an average cut off point for milk spots.

I dont think milk spots ever happen randomly, there must be a process caused by storage, a wash touching the coin etc.  Anyway I dont care about the cause as much as how long it takes to spot.  Here is a precise example/statement that I am thinking may be true.

If I buy three graded coins, all graded at NGC or wherever on the year of release.

2020 30g panda

2015 30g panda

2010 1oz panda

None of the coins have any milk spots but here is the question.  Given the age is the 2019 more likely to spot that the 2015 and the 2015 more likely to spot than the 2010

Its obvious to me that the 2020 is the most likely to spot but how long after developing no spots is it likely to never spot.  Its a tricky one to google the answer because without a long term stacker grading their coins and logging when milk spots develop its always going to involve guess work.   If I have missed something completely please feel free to correct me.

[ChrisSilver]

The truth is that there is no direct answer, spots may never develop or they may take a long time to develop. I even have a coin about 5 years old that I have only recently noticed small faint spots on, and it is a Perth Mint proof!

Spotting is usually caused by the chemicals left on a coin after production (which are clear and invisible to the eye) but after some time these chemicals left on the surface can react with the air. A variety of factors will determine if a coin will spot and how long it will take, namely how much of this chemical residue is left on the coin (impossible to tell as it is invisible) and variable factors regarding the storage of the coin / item, including the exposure to air and the humidity as well as other factors. Temparature may or may not also play a factor?

The NGC website explains it nicely on this page:

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How do I know if my modern silver coin will develop white spots?

There is no known method to determine whether a modern silver coin will develop white spots, or how large these spots will be. Some modern silver coins never develop white spots. Others develop white spots immediately after they are struck. The development of white spots appears to be entirely unpredictable.

https://www.ngccoin.uk/submit/coins-we-grade/white-spots/

There is lots of useful information on that page, so it is good to read  

I believe that encapsuled / slabbed coins also do offer some greater production in avoiding milk spots. This is just my opinion based on the fact that the holders are supposed to be air tight. However, NGC do state that there is no evidence to support this theory.

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Can white spots develop after the coin is encapsulated in NGC’s holder?

It is possible that white spots can still develop after a modern silver coin is encapsulated in NGC’s holder. Many collectors and dealers claim that modern silver coins spot less frequently after they are encapsulated in NGC’s holder and that the NGC holder is the best for preventing the development of white spots. These claims have not been scientifically verified, however, and any such evidence is purely anecdotal.

Lots of useful information on this page, so I would encourage members to read the short information here on NGC.

Some information on PCGS regarding spotting also.