Cleaning a coin

[Rob Two Spades]

I was browsing through my recent finds and saw that one of my coins is a rare 1799 pattern halfpenny of George III. Its in pretty good condition so I think I'll sell it - I can buy a pinpointer then! All the detail on the coin is fairly easy to read but Its covered in a thick grey patina, how can I get this off? I've cleaned it with WD40 and then gentle toothpaste but only the dirt has come off. Any advice?

[Chef Geoff]

WD40 and toothpaste 
I really hope your joking........If your not then I hate to say you may have devalued it already. The simple rule is, especially with copper alloy coins, don't clean them, leave it to the experts.
The greyish patina is probably bronze disease and without a long chemical process is there to stay.
Old coins are expected to have a patina and are priced on how attractive in tone this is.
If you wish to improve the tone of the patina then I would advise buying some renaissance wax. if you want to clean a bronze coin then a 1 min dip in lemon juice is all you should be doing.

[dances with badgers]

is that all you can do for cleaning coins cheff? have you ever tryed one of those tumblers for cleaning modern coins? .i recently put an old copper coin in white vinegar an salt but it completly disolved it.

[Chef Geoff]

Cotton buds, distilled water, lemon juice, a baby tooth brush, cocktail sticks and acetone is my kit for cleaning copper alloy finds, but I am only talking about unusual or good examples.
Yes I have and do occasionally use a barreling machine, they are very good for new coins and even bringing some new life to old Georgian coins that are very bad.
Taff has a thread on here somewhere showing the before and after of what seemed like a blank cartwheel penny.

[nfl]

i usually soak all bronze coins in a tumbler of olive oil for maybe a week or 2,it does leave the coins darker buy it clears the muck off and brings the detail out.

[Rob Two Spades]

I was told that WD40 does the same thing as olive oil, dissoves away peaty stains etc. Another post somewhare suggested toothpaste as a gentle way to remove dried on dirt. I'll try rubbing on some lemon juice with a cotton bud to see if it helps.

[rjm]

Cotton buds, distilled water, lemon juice, a baby tooth brush, cocktail sticks and acetone is my kit for cleaning copper alloy finds, but I am only talking about unusual or good examples.
Yes I have and do occasionally use a barreling machine, they are very good for new coins and even bringing some new life to old Georgian coins that are very bad.
Taff has a thread on here somewhere showing the before and after of what seemed like a blank cartwheel penny.

Is there a way of finding this thread?

Oddly enough I have a Cartwheel penny with some detail through the dirt and I think it would come up nice.

I've cleaned Cartwheels that were very bad before by a cloth and brasso, gentle rubbing and a bit of toothbrush. They came back to a lovely buttery copper colour which I quite like but I'd like to see what Taff recommends.

[Chef Geoff]

God that took some finding, here you go Bob.

http://www.detectingwales.com/index.php?topic=7644.msg73518#msg73518

[jonty]

For cleaning a coin without causing damage of any kind I would always go for an ultrasonic cleaner. A few years back I used one as part of my job, but recently one hasn't been available to me. This week Lidl have been selling one for 18 quid, which by any stretch of the imagination is a good deal.
This type of cleaner works roughly on the principle of a miniature but very fierce jacuzzi. It will remove any amount of dirt but that is all. It will not not make a good coin out of a bad one. Also very good for cleaning jewellery cd's and dvd's.

[outlaw]

The advice i was given a few years ago from an arkie, whatever i find, take photo's preferably in situ and just wash it under a tap with a very soft bristle brush, the most important point is to ensure the artefact / coin is dried before storing away.

Detectorists can damage finds so easily using cleaning chemicals.

Any other method is best left to an expert.