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Choice Collections College

Don't Clean It

Cleaning a coin can permanently lower what collectors will pay for it. Why it happens, what graders do with cleaned coins, and what to do instead.

If you remember one rule from the College, make it this one: don't clean your coins. Not with polish, not with a dip, not with a pencil eraser, not with a toothbrush. It's the most common well-meaning mistake we see, especially from families who've just inherited a collection and want it to "look nice."

Why cleaning hurts

A coin's original surface is part of what collectors are paying for. Cleaning removes or scratches that surface, and the change can't be undone.

Grading services mark cleaned coins with a "Details" grade instead of a numeric one. In an NGC column, Jeff Garrett described a heavily cleaned early gold coin graded "UNC Details – Improperly Cleaned" as "probably worth 35% to 45%" of the same coin with an uncleaned MS 60 grade, while a lightly affected example held "75% or more." He added: "Pencil erasers are also a very common tool of numismatic destruction" (NGC, Jeff Garrett).

Conservation guidance agrees. The Canadian Conservation Institute says dips and metal cleaners "should not be used," and removing corrosion "should be left to a conservator" (CCI).

What to do instead

  1. Leave it as it is. Toning, dirt and dullness are usually better left alone.
  2. Handle it by the edges, over a soft surface. For silver, CCI recommends cotton gloves rather than latex, "because the sulphur in latex causes silver to tarnish" (CCI).
  3. Put it in a safe holder. Avoid soft PVC flips for long-term storage; NGC warns PVC can lead to "hydrochloric acid which permanently scars the coin" (NGC).
  4. Photograph it front and back so you have a record.
  5. Ask before you act. If a coin has active corrosion or green spots, ask a conservator or a reputable professional before doing anything.

For families sorting an inherited collection

Please share this page before anyone starts "tidying up." Our Inherited Collection kit starts with exactly this step.

Try it in your portal

Add the item with photos as-is, and use the notes field to describe anything that worries you (spots, haze, residue). You'll have a record before anyone touches it.

Talk to a qualified professional

For a coin with active corrosion or damage, a professional conservator is the right person to ask. For insurance questions about damaged items, talk to your own insurance agent.

Educational only. This is not insurance, tax, legal or investment advice. Figures quoted are one expert's examples from the cited article, not a prediction for any specific coin.

Sources

Course 107

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Last reviewed 2026-10-28 · Draft