What Causes Milk Spots On Silver Coins

White spots also called milk spots are surface discolorations which sometimes mar the appearance of silver bullion products.

What causes milk spots on silver coins.

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. 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. 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.

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. 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. In many cases reports of milk spotting are on raw bullion quality 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.