Cleaning Coins: When You Should & Shouldn't (and How to Do It Safely) 2025

The first rule of coin collecting is: DO NOT CLEAN YOUR COINS. This is the most important piece of advice for any collector, new or old. Improperly cleaning a coin can instantly reduce its value by 50% to 90% or even more. Collectors prize a coin's original, natural surface and the toning (patina) it has acquired over time.

However, there is a great deal of misinformation online, and there are very specific, rare exceptions to this rule. This guide will explain why you shouldn't clean coins, the very few times it might be acceptable, and the only safe methods professionals use.

Before you attempt anything, you can use the Coinly app to get an idea of your coin's value. Knowing if a coin is valuable beforehand will reinforce why it's so important to not damage it.

Why You Should Almost Never Clean Your Coins

When you clean a coin, you are not just removing dirt; you are permanently altering its surface. Here’s what happens:

1. It Creates Hairline Scratches: Any form of rubbing, even with a soft cloth, creates microscopic scratches on the coin's surface. This damage is irreversible and instantly tells an expert the coin has been cleaned.
2. It Destroys the Original Luster: Luster is the delicate, satiny sheen a coin has when it leaves the mint. Cleaning strips this away, leaving the coin looking dull and lifeless, even if it's shiny.
3. It Removes Valuable Toning: Toning, or patina, is the natural coloration a coin develops over decades. Attractive, natural toning can add significant value to a coin. Cleaning removes this history and appeal.
4. It Makes the Coin "Un-gradable": Professional grading services like PCGS and NGC will not assign a numerical grade to a cleaned coin. Instead, it will be returned in a "details" holder, labeled as "Improperly Cleaned," which severely lowers its market value.

In short, a shiny, cleaned coin is almost always worth less than a dirty, original one.

The Very Rare Exceptions: When is Conservation Acceptable?

In the professional world, the term "cleaning" is avoided. Instead, they use the word "conservation." This is only acceptable in a few specific situations and should ideally be done by a professional.

• Removing PVC Residue: Old, soft plastic flips contained PVC, which can leach onto a coin's surface, creating a green, sticky slime. If not removed, this can permanently damage the coin. This is one of the few times intervention is necessary.
• Removing Loose Debris: If a coin has loose dirt, sand, or other non-attached debris on its surface, a gentle rinse may be acceptable.
• Conserving Dug Coins: Coins found metal detecting are often covered in thick dirt. Even then, the methods used are extremely gentle and non-abrasive.

Safe, Professional Coin Conservation Methods ONLY

If you absolutely must intervene, these are the only methods considered safe. Remember, these methods can still cause damage if done improperly. Proceed with extreme caution.

Method 1: Pure Acetone Bath (For PVC or Organic Residue)

This is the go-to method for professionals to remove PVC slime or other organic gunk.

• What You Need: 100% pure acetone (not nail polish remover), a glass container, and cotton swabs.
• Process:
  1. Place the coin in the glass container.
  2. Pour enough pure acetone to fully submerge the coin.
  3. Let it soak for a few minutes to a few hours. The PVC residue should dissolve.
  4. Do not rub the coin. If needed, you can gently roll a water-soaked cotton swab over the area to lift the residue.
  5. Rinse with fresh acetone and let it air dry completely. Acetone evaporates quickly and leaves no residue.

Method 2: Distilled Water Rinse (For Loose Dirt)

This is for removing loose, non-caked-on dirt.

• What You Need: Distilled water (tap water contains minerals that can spot the coin).
• Process:
  1. Create a gentle stream of distilled water.
  2. Hold the coin by its edges under the stream.
  3. Let the water flow over the coin to wash away any loose particles.
  4. Do not rub it.
  5. Pat dry gently with a very soft, lint-free cloth, or let it air dry.

What to AVOID at All Costs

Never use any of the following to clean your coins. They are all abrasive and will destroy the coin's surface and value.

• ❌ Coin polishes or dips (like Tarn-X)
• ❌ Toothpaste or baking soda
• ❌ Brushes (even soft toothbrushes)
• ❌ Erasers
• ❌ Ultrasonic jewelry cleaners
• ❌ Ketchup, lemon juice, or any acidic substance

The Verdict: When in Doubt, Do Nothing

The safest and most profitable strategy is to leave your coins as they are. The natural patina and signs of age are part of a coin's history and are what collectors value. A cleaned, shiny coin is a damaged coin in the eyes of a numismatist.

Before you ever consider any conservation efforts, use the Coinly app to identify your coin and get a sense of its potential value. More often than not, you'll find that its value is highest in its original, untouched state.

This guide is for educational purposes. Any attempt to clean or conserve a coin carries risk. For valuable coins, always consult a professional conservator from a service like NCS (Numismatic Conservation Services).