Milk spots on silver coins

We are often asked about milk spots on silver coins: What are they? Do they affect a coin's value? Can they be removed?

Milk spots are marks that appear on the surface of a silver coin. The white or off-white colouring bears a resemblance to milk – hence the name. Spots are generally quite small, but can sometimes be larger, concentrated groupings that can look quite unappealing visually. They can be found on new coins direct from the mint, but can also appear on older coins too.

A photo of an Austrian silver Philharmonic coin with milk spotting. Photo courtesy of Silver Torch66 via Flickr.

Milk spots are not a concern for silver as a bullion investment. They are a tarnishing of the metal but they do not damage or erode it. This isn't ideal for presentation purposes but as a physical asset it won't affect sale value. This is usually something avoided by collectors however.

What causes milk spots on silver coins?

The general consensus is that milk spots are an inherent part of the manufacturing process. Before being stamped with the design, the blank or planchet is cleaned using a variety of chemicals to help ensure as high quality a finish as possible. The coin is then heated and cooled – annealed – to help ensure it does not become brittle.

If the chemicals have not been fully removed prior to annealing, it can leave a residue on the coin. This leaves the coin looking perfect upon minting, but over time the residue can slowly react, causing milk spots to appear on the coin.

There are other thoughts however on what causes the milk spots to appear, from handling through to storage. Any contamination seems to increase the chance of the spots appearing, but with encapsulated coins still showing signs of the problem, there is little evidence for a single cause.

Unfortunately, milk spots are a common occurrence, and can affect all modern bullion silver coins and even bars. Knowing which silver will be impacted is not possible, and frustratingly for collectors even coins sealed in their capsules can exhibit milk spots in the future without warning.

The Royal Canadian Mint has investigated milk spots and developed a proprietary solution known as “MINTSHIELD” surface protection. This is now applied to their silver Maple Leaf coins and so far, the results do suggest a reduction in milk spotting, giving some hope for the future.

Another example of milking. Image courtesy of user D4N on The Silver Forum.

Will milk spots affect the value of a silver coin?

For a bullion coin, the good news is that milk spots will not impact the resale value of the coin. An ounce of silver is still an ounce of silver whether it has a perfect finish, scratches, or even the notorious milk spots. This means that investors can buy silver without worrying about milk spots appearing, and that they will still be able to sell them back to dealers in the future at the same price.

Collectors buying Proof silver however will usually be much more concerned by their appearance, as the perfect finish is often part of the appeal of a collectable coin, and milk spots could impact the value as a result.

How to remove milk spots on silver coins?

There are differing opinions on how to remove milk spots from silver coins, with mixed results. The general consensus for removing milk spots remains the same for cleaning any coins however – it should be avoided if possible.

Any efforts to remove milk spots will more than likely replace the spots with small scratches, which only end up having a worse impact on the look of the coin. Again, for a bullion coin the scratches would not affect the resale value, but neither would the milk spots so we would always recommend saving yourself the time and trouble of replacing one blemish with another.

Collectors have had some luck with chemical dips, or the use of a pencil rubber. Given the potential for damage however there will always be an element of risk in trying to remove them, and even professional services will likely not guarantee a perfect clean without any damage.

Hopefully, as minting technology continues to evolve in the coming years and decades, milk spots can eventually be eradicated from the process. In the meantime however, much in the same way silver tarnishing is positively referred to as 'toning', so too can milk spots be accepted as a common occurrence and in some ways as further proof of the authenticity of the silver being used in bullion coins.