Cleaning Coins and Artefacts

5th March 2015 — 16 Comments

dreamstime_3947474John is about to enter another minefield. I know a detectorist who regularly ‘cleans’ his coins in a barrelling machine. Every coin. Luckily, he hasn’t yet unearthed a historically important item. He prefers that his finds be abraded in this way. Afterwards he smears them liberally in some sort of ‘preserving’ gunk leaving them with a strange green-like glistening hue. I’m not sure that he knows, but he is universally referred amongst his friends as Mr. Shiny. Our friend is revered on detecting forums because the knowledge he has gleaned over many years of metal detecting is second to none. Just, don’t seek his advice on cleaning.

I’m reminded of something detectorist Neil Allen said in a conservation group meeting at the British Museum, whose proceedings, Whose Find is it Anyway? was published in 2006. He said:

“In the past, conservators were aloof … so this left the market open for publications by enthusiastic amateurs. Unfortunately, some of their advice was not of a high standard … these publications gave instructions on how to use a barrelling machine. It comes in three sizes: destruction, total destruction and universal Armageddon – and you can turn destruction into universal Armageddon by leaving it on longer!

They went on to show how to burn away patina my using acids and then had to repatinate using flowers of sulphur and petroleum jelly. Good stuff isn’t it? You could clean silver coins using washing soda, aluminium foil and boiling water. Excellence for your choice and medieval finds. It went on to explain that you should coat your find with olive oil and shine up the remaining gold gilding with lemon juice.

Olive oil and lemon juice – it doesn’t sound like conservation … it sounds like the beginning of a Jamie Oliver salad dressing. Another idea was bead-blasting iron objects I won’t go on … it’s too horrible.”  Neil Allen 

Your Starter Cleaning Kit


I don’t know where I first read it, but there’s a great piece of advice in a saying that tells us that cleaning coins is like marriage and shouldn’t be embarked on lightly. Or have I just made that up? Translated, that simply means DON’T DO IT! It’s far better to have a dirty coin with it’s original patina, than have one that is irretrievably damaged.

adviceConservation Advice from the PAS

As a rule of thumb, the older the item, the more heavily corroded it will be, and many ancient objects made from copper alloy will have developed a patina which adds value and beauty to the object. Removing this patina could seriously damage and devalue the object and destroy information. But many of your finds will be fairly modern, like milled coinage, watch-fobs, penknives and other casual losses. These more recent items can mostly be cleaned carefully without them coming to harm but there are no ‘quick fixes’!

You can download Conservation Advice from the Portable Antiquities scheme by clicking HERE

I firmly believe that the cleaning of any item should not be entered into without the utmost care. I have cleaned items myself, but only used warm water and a mild household detergent. I usually leave any cleaning in the expert hands of Mrs. John.


© Coin Yearbook – Click to enlarge


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16 responses to Cleaning Coins and Artefacts

  1. With so many new detectorists entering our hobby, it is extremely important for them to know these facts in your blog.

    Use a tumbler only for modern coinage!

  2. Nice read once again John, enjoy browsing through everything you put out there.

  3. Very good post John, so many have no idea.

  4. Like you, I only use soap and water John but I frequently see stuff on the web ( a bronze age axe head recently) wrecked by overzealous cleaning and giving plenty of ammunition to the antis.

  5. A good toe-curler there, John! And essential advice… Thank you!

  6. Anyone who read the recent series in the Searcher, on the subject, will have been left with no illusions.
    Thank you for this John

  7. The thing is if you don’t stabilise bronze decay on the likes of Roman bronze coins and bronze brooches make no mistake you will eventually be left with a heap of green dust, the only ‘preserving’ gunk I use is the natural bees wax product “Renapur” it kills bronze decay with one application and I only do this treatment with the low interest crap finds.
    Although I have a tumbler I wouldn’t dream of putting in any ancient or valuable finds I have only used it on beech found modern coins and this is only after the occasional beech detecting session.
    I hear people saying never clean your finds but I visit York Coin Fair and there is hundreds of thousands of coins on display and not one of them has any sign of residues or crud left on them so who is indulging in this taboo cleaning behind closed doors.
    Mr. Shiny. might have the right idea.

  8. I thank you all for the comments … didn’t get around to mentioning the Dremel machine and Coke etcetera … perhaps the premature posting was an early warning that I was venturing too far into the minefield.

    • I’ve just been reminded that I didn’t mention the Brillo Pad!

    • May I ask a question of you John or perhaps your subscribers on the subject you eloquently wrote?

      Now I own a fairly large collection of mainly milled silver and bronze coins and gain pleasure from their natural darkened and colourful appearances, although in no way do I regard myself as a numismatist. The question is this;

      Is it purely the colour or is it the thought of peoples long gone, who have left a small piece of themselves from the oils and dirt of their hands, which over time created this patina,, which appeals to the numismatist? I ask this because I have seen on MDing forums artificially produced patinas, which don’t quite look right or have the sense of historic contact with our predecessors.

  9. I make jewellery and occasionally use a product that is routinely used in the jewellery trade on the likes of copper, to preserve my finds with.

    It’s called Renaissance Wax, and it was actually developed in association with experts from the British Museum in London.

    It won’t damage your finds in any way, but coats them in a clear wax protecting them from atmospheric conditions, greasy fingers, and anything else. Excellent stuff.


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