Milk spots can occur on both bullion and collector coins struck in proof and burnished uncirculated finishes but they are substantially more common on bullion silver coins with 999 or higher purity and are not seen on older coins with alloys such as pre 1964 u s.
What causes milk spots on silver coins.
When a coin is manufactured one of the final processes that it goes through is annealing a system of baking and cooling the coin in order to prevent the silver from becoming brittle.
In this video we talk about the white spots or milk spots that are found on some government silver bullion like the maple leaf and american eagle.
Milk spots may be caused by a problem with the planchet or due to the coin having been exposed to polyvinyl chloride pvc.
Milk spots are those obnoxious thin white marks that arise on reflective silver coins caused by the annealing process.
Many collectors of modern silver bullion coins are familiar with the occurrence of white spots or milk spots as they are often called in numismatic vernacular.
In many cases reports of milk spotting are on raw bullion quality silver coins.
These white spots can sometimes develop on a variety of modern silver bullion coins from around the world including american silver eagles chinese silver pandas and canadian.
Unlike tarnishing which is a by product of oxidation white spots don t have a single predictable cause and this has complicated the search for an effective solution to a problem affecting silver bullion coin.