What Are Milk Spots & How Do They Affect the Value of Silver Coins?

Milk spots are white, cloudy marks that can appear on the surface of silver coins and bars – even on untouched pieces that have been stored in pristine condition. While they don’t affect a piece’s metal content, they can understandably be a source of concern for silver investors and collectors.

In this article, we explore what silver milk spots are, how they form, and whether they have any impact on the value of your silver bullion. We also look at what steps (if any) you can take to prevent or remove them, and how a few mints are responding to the issue.

What are milk spots?

Milk spots are cloudy white marks that sometimes appear on the surface of silver coins and bars. Just as their name implies, these spots often look like dried milk and can range in size from faint patches to larger, more noticeable blotches. Milk spots on silver are harmless and don’t actually affect the underlying metal, but they are permanent and many collectors find them visually unappealing.

Milk spots most commonly appear on modern silver bullion coins with a high purity, usually 99.9% or higher. They can also be found on proof coins, although it’s less common. Older coins, made from silver alloys, tend to be less susceptible to these milky marks. This is thought to be due to differences in composition and minting techniques.

At the end of the day, milk spots are kind of random and can sometimes even form in sealed, untouched packaging. For that reason, they can be a source of frustration for investors who are unsure what caused them and how they can be removed.

Where do milk spots come from?

It’s not entirely clear how and why milk spots form, but most experts believe they develop during the minting process.

Before being stamped with a design, silver blanks (or planchets) are cleaned using various chemicals to help give them a high quality finish. The coins are then heat-treated and cooled (a process known as annealing) to prevent them from becoming brittle. If the cleaning chemicals aren't properly removed before the annealing process, it's believed they can leave a residue on the coin. Over time, this residue can react with the metal and gradually form the white marks we call milk spots.

There are other possible factors that play a role with milk spots, such as airborne contaminants, human handling, or improper conditions during long-term storage. It seems that any form of contamination can increase the chances of milk spots forming, but there are cases where they’ve even appeared on coins kept in sealed capsules or untouched mint packaging.

Whatever the cause, milk spots on silver coins are known to be unpredictable and can appear anywhere from days to months or even years after a coin is minted. They’re not limited to any specific coins from any singular mint, and they also appear on silver bars, making it harder to pinpoint a single reason behind them.

Read: What is Silver Stacking?

How to prevent milk spots

Unfortunately, there’s no guaranteed way to prevent milk spots from appearing on silver coins or bars. Since these marks often form during the minting process, even storing coins in perfect conditions can develop them over time.

That said, some investors and collectors believe that you can reduce the risk of milk spots by taking care with storage and handling. For example, using airtight capsules or containers can limit exposure to air, moisture, and dust, which might speed up the appearance of spots. You can also wear gloves before handling both bullion coins and bars to avoid direct contact with the metal’s surface and protect the coin from fingerprints or other contaminants.

That said, remember that even coins kept in pristine, sealed packaging have been known to develop milk spots over time, so taking these measures might not work 100% of the time.

What are mints doing about milk spots?

Since milk spots are believed to be a result of the manufacturing process, some mints have taken steps to address the issue – namely the Royal Canadian Mint and the Perth Mint.

In 2018, the Royal Canadian Mint introduced MINTSHIELD™, a proprietary surface protection treatment that’s applied to Silver Maple Leaf coins. The exact formula for the treatment (and how it works) are kept secret, but MINTSHIELD™ is designed to reduce the appearance of milk spots without changing the coin’s look or precious metal content. So far, it’s shown promising results in preserving a coin’s appearance for the long term.

In fact, the Royal Canadian Mint even tested this technology on a bunch of coins in 2018. In the test, Silver Maple Leaf coins were subjected to accelerated aging in a hot, humid environment to simulate extended periods of time. Compared to other bullion products on the market, these coins showed no signs of white spots on the obverse or reverse.

The Perth Mint has also made adjustments to its production process to help reduce contamination, such as improving air filtration to reduce airborne particles and regularly cleaning machinery to remove oil and water build-up. These efforts might not eliminate milk spots entirely but the idea is to lower the chances of them forming.

Do milk spots affect the value of silver coins?

Now for the real question – do milk spots affect the value of your silver coins? If you’re a bullion investor, you’ll be happy to know that milk spots do not affect a coin’s resale value. Because silver coins are valued for their metal content (as in their weight and purity) rather than their appearance, an ounce of silver is still an ounce of silver, even if its surface shows minor blemishes like milk spots. This means that most dealers won’t discount a silver coin just because it has these marks.

That said, coin collectors might have a different perspective. Proof finished coins and other collectible silver pieces often carry higher premiums due to their mirror-like finish, quality, or intricate design. In these cases, visible imperfections like milk spots might affect a coin’s appeal and lower its numismatic value on the collector market.

In short, if you’re a long-term investor focused on the metal itself, milk spots are just a cosmetic issue. They might not look the best, but they won’t change the intrinsic value of your silver investment.

Keep Reading: What is a Proof Coin?

Can milk spots be removed?

Another big question investors have is whether milk spots can be removed. It might be tempting to try and clean up your coin, but most experts will advise against it. Why? Because many attempts to clean or polish a silver coin – especially using abrasive materials or chemicals – might end up damaging its surface even more. In most cases, you’d essentially be trading one flaw for another (milk spots for fine scratches or dulled finish).

Since milk spots don’t really affect the metal content or resale value of bullion coins, it’s rarely worth taking the risk to remove them. You’re generally better off leaving them as they are, especially for investment-grade silver where visual appearance isn’t as important as weight and purity.

If you look online you might find some collectors experimenting with different methods to remove milk spots, like using silver polishing cloths or soft white pencil erasers. These techniques can sometimes reduce the appearance of spots but they can also alter the coin’s surface and should be used with extreme caution, especially on proof or high-premium coins.

Some professional dealers use silver dip or a chemical solvent to remove milk spots. This might work on silver bullion coins, but can be a real risk with proof coins as their highly polished surface is more sensitive to change. In many cases, even these professional coin restorers won't fully guarantee removing milk spots without the risk of damage or degradation.

Essentially, until minting techniques improve and eradicate this problem for good, milk spots will simply remain an aspect of owning silver bullion coins. Thankfully, the issue is widely recognized and accepted, so if you’re facing the problem, you’re not alone.

Which silver coins are most susceptible to milk spots?

Milk spots can technically appear on any silver coins, however some investors have noticed that they seem to be more common with certain coins and mints. These include pre-2015 Royal Canadian Mint and Royal Mint coins, such as the Silver Maple Leaf, Silver Britannia, and coins from the Silver Queen’s Beasts series. Silver Vienna Philharmonics are also believed to develop milk spots more commonly compared to other coins.

Some investors believe that coins with mirrored fields are more prone to developing milk spots compared to those with a more frosted surface, however again, the reasoning behind this isn’t really clear or certain. At the end of the day, this information shouldn’t prevent you from purchasing any of these coins as milk spots are largely unpredictable and can happen to any silver coin, any time.

Milk spots vs toning on silver coins

Milk spots and toning are both types of discoloration that appears on a silver coin’s surface over time, but they are very different.

To recap, milk spots are bright white or cloudy marks that form during the minting process, potentially due to chemical or physical contamination. They tend to appear unpredictably and sometimes even appear on sealed coins. Once they form, they’re difficult (or even impossible) to remove without risking further damage to a coin.

Toning, on the other hand, is a natural response when silver reacts with air, moisture, or sulfur compounds over time. It’s a thin layer that changes the colour of a coin’s surface, sometimes adding shades of gold, blue, or purple. Unlike milk spots, toning isn’t considered a flaw, and some collectors actually seek out toned coins for their unique appearance.

So while milk spots might be considered a cosmetic defect – especially when it comes to proof coins – toning is often appreciated as a sign of natural aging and character.