How to clean metal detecting finds — and when not to

Last updated: 17 October 2026

The most important rule of cleaning finds is knowing when not to. Aggressive cleaning destroys both the object and its history — and it can wipe out the value of a good find in seconds. For most finds, less is more: a gentle rinse and a soft brush, at most. Anything that might be treasure, or that's old and fragile, should not be cleaned at all — show your Finds Liaison Officer first. This is the conservation-led approach the Portable Antiquities Scheme recommends.

In short

The first rule of cleaning is knowing when not to — over-cleaning destroys finds and their value, and it can't be undone.
Never clean a potential treasure find. Leave it as found and report it within 14 days.
For sturdy finds, keep it minimal: a rinse in clean water and a soft brush, then air-dry. Nothing more.
Never use acids (vinegar, lemon, cola), abrasives, wire brushes, metal polish, electrolysis or ultrasonic cleaners.
Don't strip the patina off a coin — it holds the detail and most of the value; removing corrosion is a job for a specialist.
Iron and actively-corroding bronze are fragile — don't soak or scrub them; keep them dry and get advice.
When in doubt, don't — record the find as it is, and ask your FLO or a professional conservator.

The first rule: when not to clean

It's tempting to scrub a muddy find until it shines, but that instinct ruins more good finds than anything else in the hobby. Cleaning is irreversible: the surface of an old object — its patina, the subtle toning and the mineralised layer built up over centuries — carries the detail, the archaeological information and, for collectors, most of the value. Strip it off and you can turn a museum-quality coin into a worthless disc in a few minutes. The professional standard, set out in the Portable Antiquities Scheme's conservation advice, is minimal intervention: do the least that's needed, and when in doubt, do nothing.

Should you clean this find?

Before you touch a find with anything, decide which kind it is. This is the whole decision in one place:

Whether to clean a find — and what to do instead.
The find	Clean it?	What to do
Might be treasure (old gold or silver, a hoard, anything significant)	No — never	Leave it exactly as found, handle it as little as possible, report it within 14 days and show your FLO.
Old, fragile, iron, or actively corroding	No	Keep it dry and stable; get advice from your FLO or a professional conservator before anything else.
A sturdy find caked in soil (e.g. a bronze buckle)	Gently, minimally	Rinse in clean water with a soft brush, then air-dry — and stop there.
A coin with patina or surface detail	Barely	Rinse off loose dirt only; never try to remove corrosion or brighten the surface.

The safe minimum for sturdy finds

For a robust object that is clearly not treasure and not fragile — a solid bronze buckle, a lead weight, a modern coin — a little cleaning to see what you've got is reasonable. Keep it to the gentlest thing that works:

Let caked mud dry, then lift it off gently with a soft brush (an old toothbrush or a soft artist's brush).
If more is needed, rinse in clean, lukewarm water and brush softly — fingers and a soft brush only, no scrubbing.
Pat dry and air-dry fully before storing, so no moisture is trapped. Store in a dry place, ideally with a little silica gel.

That really is the whole safe repertoire. If water and a soft brush don't reveal the find, the answer is not a harsher method — it's to stop and ask for advice.

What never to do

These are the methods passed around online that quietly destroy finds. Avoid every one of them on anything you care about:

Acids — vinegar, lemon juice, cola and proprietary "coin dips". They etch the metal and strip the patina, permanently.
Abrasives — wire brushes, wire wool, scouring pads, sandpaper, abrasive pastes. They scratch away the surface and the detail with it.
Metal polish and buffing — polishing a coin or artefact bright destroys its patina and its value at a stroke.
Electrolysis — effective at stripping metal, and far too aggressive for anything old or valuable.
Ultrasonic cleaners — the vibration can shatter fragile or cracked objects.
Picking and scraping with knives, screwdrivers or other metal tools, which gouge the surface.

Different metals, different risks

Materials behave very differently in the ground and out of it, which is another reason a single "cleaning method" is a bad idea:

Iron is the most fragile — it's often more corrosion than metal, and water accelerates it. Don't soak or scrub iron; keep it dry and let a conservator stabilise it.
Bronze and copper alloys can develop active "bronze disease" — bright, powdery green spots that keep eating the metal. Don't try to treat it yourself; keep the object dry and separate and get advice.
Silver usually carries a toning or patina that's part of its character and value — never polish it bright.
Gold is chemically stable and often just needs loose soil rinsed off — but if it might be treasure, leave it alone.
Lead and pewter are soft and scratch and dent easily, so handle them gently and keep abrasives well away.

Potential treasure: don't clean it

If a find might be treasure, cleaning is not your decision to make. Leave it exactly as you found it, handle it as little as you can, and report it to the coroner within 14 days — in practice through your Finds Liaison Officer. Cleaning can destroy evidence that matters to how the find is understood and valued, and a conservator working for the receiving museum will handle it properly. What counts as treasure, and how reporting works, is set out in our guide to the metal detecting laws in England.

When to call a conservator

For anything significant, old, fragile or actively corroding, the right move is to leave it to a professional. Your Finds Liaison Officer is the first port of call — they can tell you whether a find needs a conservator and point you to one, as well as record the find for the Portable Antiquities Scheme. For accredited conservators you can also use the Institute of Conservation's Conservation Register. It is always cheaper to ask first than to undo damage afterwards — because, with cleaning, you can't.

Record the find before you touch it

Good practice — and good conservation — starts in the field: photograph a find as you found it, note where it came from, and leave the cleaning decision until later. Muld keeps a private find journal on your own phone — photo, position and notes — so the record is made before any cleaning, ready for your Finds Liaison Officer. It doesn't report to the Portable Antiquities Scheme for you; it's your own field record. The core app is free.

Get it onGoogle Play Download on theApp Store

Common questions

How do you clean metal detecting finds?

Minimally. For a sturdy find that isn't treasure or fragile, let caked mud dry and lift it with a soft brush, or rinse in clean water with a soft brush and air-dry — that's it. Never use acids, abrasives, wire brushes, polish, electrolysis or ultrasonic cleaners, and never clean anything that might be treasure or that's old and fragile. When in doubt, leave it and ask your Finds Liaison Officer.

How do you clean old coins without damaging them?

For a dirty but sturdy coin, rinse off loose soil in clean water with a soft brush and pat dry. Do not try to remove corrosion, polish it, or use vinegar, lemon or cola — the patina holds the coin's detail and most of its value, and stripping it is irreversible. Significant or corroded coins should go to a conservator, not your kitchen sink.

Should you clean metal detecting finds at all?

Often not. The safest approach is minimal intervention: remove loose soil and no more. Over-cleaning destroys archaeological evidence and value, and it can't be undone. Anything potentially treasure, old, fragile or corroding should be left as found and shown to your Finds Liaison Officer.

Can I clean coins with vinegar or lemon juice?

No. Acids like vinegar, lemon juice and cola strip the patina and etch the surface, destroying detail and value permanently. They are one of the most common ways good finds get ruined. Use clean water and a soft brush at most, and leave anything valuable to a specialist.

How do you clean a find that might be treasure?

You don't. Leave a potential treasure find exactly as you found it, handle it as little as possible, and report it to the coroner within 14 days — in practice through your Finds Liaison Officer. Cleaning can destroy evidence and reduce its value, and once a find may be treasure it isn't your decision to clean it.

Is it safe to clean iron or bronze finds?

Be very careful. Iron is fragile and can fall apart if soaked or scrubbed, and bronze or copper can develop active corrosion — "bronze disease" — that keeps spreading. Don't try to treat either yourself: keep them dry and stable and get advice from your Finds Liaison Officer or a professional conservator.

Official sources

This page is a plain-language summary of good conservation practice, not a substitute for professional advice. If a find matters to you, ask a specialist before you do anything to it — cleaning can't be undone.

Portable Antiquities Scheme — conservation advice for finders The PAS's guidance on assessing, cleaning, handling and storing finds, written for detectorists.
Code of Practice for Responsible Metal Detecting in England and Wales The official standard — including minimal cleaning and not cleaning potential treasure.
GOV.UK — Treasure The duty to report treasure within 14 days — and why a potential treasure find should be left as found.
Icon — the Conservation Register Find an accredited professional conservator, from the Institute of Conservation.

A note on accuracy. We've based this on the Portable Antiquities Scheme's conservation guidance and standard practice, but it's a summary for detectorists, not a conservation manual. If anything here looks out of date or wrong, tell us at hello@muld.dev and we'll fix it.