Ruining a find is far easier than finding one. That is not a figure of speech: half an hour with an abrasive will write off a coin that spent two hundred years in the ground and came out perfectly readable.
So restoration has a step zero that beginners skip — deciding not to clean. Everything below is about making that decision well.
If the object has only just come out of the ground, there is one more step before that decision — the first 24 hours after a find: how to get both the object and what you know about it to the table without losing either on the way.
Reversibility decides everything
The test is simple: can you change your mind? Soak something in soap and think better of it, and nothing has happened. Take sandpaper to it and think better of it, and the relief is gone for good.
Hence the golden rule: if you are unsure, don't clean. A dirty but readable object beats a shiny pitted one every time. Dirt comes off later. Pits never do.
When not to start at all
- Rarities, and anything you plan to sell, until you have practice on things that don't matter.
- Even, stable patina — especially on silver. That patina is the value.
- Thin or cracked pieces: chemistry will finish what the soil started.
- Anything with an inset — stones, enamel, glass. Those get their own rules in special cases.
When cleaning genuinely helps
There are three honest reasons to pick up a find.
The first is a study piece whose legend is unreadable and you need to know what it even is. The second is active bronze disease, where doing nothing is itself destructive — the object is literally crumbling. The third is iron that will otherwise fall apart, and that one is only worth starting if you are ready to consolidate immediately: without a barrier it all comes back within weeks.
Six do-no-harm rules
- Minimum intervention. Soap and mechanics come before you remember chemistry exists.
- Reversibility. Do not burn away relief with an abrasive to save an afternoon.
- One metal, one bath. Copper and silver in the same tank will do galvanic damage to each other.
- Document. A "before" photo in Discovera is worth ten recollections of "I think there was something like a crest there".
- Test the hypothesis on pixels. If you want to see how it might turn out, an AI preview only risks a file.
- Finish with protection. Dry it, seal it. Skip that and the cleaning undoes itself.
Restoration begins with the decision to do nothing
Minimum intervention is not passivity. It is a deliberate decision to preserve both the object and the information around it until the material, the condition and the purpose of the work are clear. If the object has only just been lifted, record its as-found state first. If the material is mixed, the surface is unstable and the storage conditions are unknown, the right first move may well be observation and a second opinion, not treatment.
Every intervention needs a purpose you can write down in one sentence: stop the activity you can see, keep the legend readable without removing the patina, get the object ready for safe storage. "Make it prettier" is not enough, because it gives you no criterion for stopping.
Deciding to do nothing for now is itself an action: it has a date, a recorded condition and a scheduled next inspection. How that is kept is in monitoring after conservation.
Patina or disease
A good share of ruined coins are somebody removing "the green stuff" that was in fact a protective layer. Dense, even patina has sealed itself and keeps the metal out of contact; loose light-green powder is the opposite — it eats the metal.
If you cannot reliably tell them apart, that is normal, but it means stop and take the softest route. The corrosion layers are broken down in chemistry.
Decision tree: what comes first
Before you choose a method, look at the object and be honest about what you actually see. Observation sets the first route, not what metal the thing is supposed to be.
| What you see | First route |
|---|---|
| The material is unclear | Photographs, a condition card, identification or a second opinion; no reagents |
| Wet organics, glass, enamel, plating, a composite object | Stop active treatment, get a specialist assessment |
| A maker's mark, inscription, painted decoration, gilding or silver plating | Photograph under raking light; do not open the surface up mechanically |
| Loose, spreading or recurring corrosion | Isolate it, keep a conservation log, assess salts and storage conditions |
| An ordinary stable object of known material | The article for that metal — and the checklist before you start, so you stay inside the limits of the method |
Before you run the water
- Metal identified — or the gentlest route chosen because it isn't.
- "Before" photo taken.
- Any suspicion of rarity → leave it alone.
- You know how this ends: drying and consolidation.
- The rest of the collection is out of the room, away from fumes.
Water is not a neutral step: it mobilises salts and starts processes you will then have to stop. What actually happens on contact with water, and why "rinse and dry" is not a general rule, is in water, salts and hydrolysis.
External orientation
The general museum reference for handling metal is Canadian Conservation Institute — Care of Metals: storage conditions, stabilisation, minimum intervention. Hobby cleaning does not replace it and does not pretend to.
FAQ
How should any cleaning start?
With a photograph, not a reagent. Then laundry soap, a soft brush and distilled water. Acid "because it's faster" is the worst available first move.
Copper / silver / iron?
Each metal has its own logic; there is no universal recipe:
- Copper and bronze — protect the patina, treat chlorides with sesquicarbonate.
- Silver — citric acid or thiourea, and leave rarities alone.
- Iron — electrolysis, with consolidation immediately after.
- Electrolysis step by step — bath, polarity, salt rinses.
Is preservation always required?
Yes. The moment you lift the crust, the metal is open to air and moisture again — you have essentially returned it to the day it came out of the ground. Preservation closes that; the checklist stops you forgetting.
Can I preview cleaning?
You can, and it is the cheapest way to change your mind: Discovera AI cases work on a photograph and leave the original untouched.
Special cases (bi-metal, stones)?
With stones and enamel you don't use chemistry at all — the solution loosens the setting and the stone stays in the bath. Details in special cases, the underlying theory in corrosion chemistry.