Cleaning Finds" section of a metal detecting site near you. These people clearly have no idea about how to handle ground-dug metal objects. Here's one ungrammatically-named thread which is fairly symptomatic of the problem ("Restoring the patina on an over cleaned bronze coin?").
Ollie-C from Suffolk (Thu Apr 16, 2015 4:07 pm): I found my best bronze coin 4 months into the hobby but I didn't realise it at the time and stupidly over cleaned it stripping off all of the original patina, I have learnt my lesson! [emoticon, emoticon] Is there anyway [sic] I can restore the look of the original patina without purchasing any funky chemicals etc? I'd like to achieve a black/brown finish ideally, similar to how it came out of the ground. I currently have it in olive oil, but I'm not sure that will work? [sic] Pics of said coin (Celtic unit) are below.Hmm, and it is "in olive oil" for what purpose? Let's see how many respondents start with saying he needs to degrease it and get the organic acids out from the porous structure visible in the photo before doing anything else. Basically nothing on earth can ever "restore the patina" on the ruinously pitted and stripped coin shown in the photo. Nevertheless his metal detecting comrades are optimistic:
Allectus: "The tannin in tea is a powerful dye".
Ollie-C: "As evident inside a colleagues tea cup! [emoticon] So, make a nice black brew and let it soak for a bit? Cheers"
Fusion "You could try the 'put it in the oven' method, as described in this thread".
Ten pence! "You can buy a product called Brass Black which is used in the gun trade for er... turning brass or copper black or alternatively you can get some household ammonia which is relatively inexpensive and either mix some with some sawdust to dampen it then seal it in a container for a day or so, or suspend the coin by wire in a glass with a small amount of ammonia in the bottom, (the fumes turn copper green)and seal the top with cling film. Although in truth it's very hard to replicate what you've strip off".
Especially as the coin shown has been electrochemically stripped to a pitted raw metal core. It's what we call in the profession "totally buggered".
Danzigman: gives a link to a metal detecting website.
Davybfast: adds ungrammatically and unhelpfully: "just washed my cup or I would have took a pic of the inside. lol".
Ravenrook is already confused: "Sounds like a complete minefield to me!! Be very careful you don't make it worse! I'd speak to a pro in a jewelers if I were you". Yeah, they do fings wiv metill don't they? Yeah.
Glenfiddich: "simple way would be to just stick it back in the ground for the next 50 - 100 years and see if that'll do anything [emoticon] sorry mate but seriously......I've no idea [emoticon] and as you already said that you've learned your lesson [emoticon] :( cheer up mate 50 - 100 years will fly in before you even know it, lol [emoticon] ". The damage OllieC has done to this archaeological object is totally irreversible. He basically has destroyed a large part of it.
bbuster88 "Hi Ollie, found myself asking the same when I was over cleaning [emoticon] tried: liver of soulful witch to be honest just stunk my kitchen out [emoticon] didn't go down to well, then danzigman recommend JAX PETINA SOLUTION, I'll put the link for you [Noble Roman coins], anyway works brilliantly, there's no smell and if you go for the 4 then you have the choice green/black/brown.... Works in around 20/30 seconds [emoticon]". That "soulful witch" who lost her liver in this guy's kitchen worried me, until I realised the semi-literate meant "liver of sulphur".... hmmm.
Cobs [OMG!]: "You could try reverse-electrolosis, im sure that would darken the metal instead but have a read up on that first, been a while since i used electrolosis, failing that you could seal it with black boot polish". I think boot polish is preferable to metal plating by a half brain. But then since the artefact is totally gone... go on Ollie finish the job, and post a video of it.
Ollie-C is grateful: "Thanks for all the advice, lots of different ways of potentially doing it then! I've currently got it soaking in tea. I'll report back with my findings [emoticon] I haven't got the patience to stick it back in the ground for 50-100 years [emoticon]"
Ulvir (I knew this one was coming): "Put it in a dung heap for a while - works a treat.. "
Ten pence! forgets he gave his "ammonia in a glass" idea, so repeats it. ("put the coin/relic in the cup and bury it in the sawdust").
bbuster88 tries to sell something: "I have the jax 4-pack for sale from us, without doubt the best for touching up or completely re-patination products and save a coin, link at bottom, [emoticon] Without sounding a di@k just wash your coins with a bit of washing up liquid END OFF [sic] ! Really I've learnt my lesson [emoticon] pm me if interested buddy [emoticon] [Noble Roman coins link again]
targets returns to the organic gardening method: "poke it in a cow pat and leave for 3 months in the garden".
Note that not a single one of them pointed Ollie to something called a "book", or indeed the PAS webpage with advice on handling ground-dug metal artefacts.
Vignette: Now wash your hands, you don't know where that coin has been.