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Conserving Detected Dug Coins & Relics


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As us European detectorists dig up a wide variety of stuff, from 3000 BC to present-day, made of all manner of metals, I suggest registering with one of the better-known UK forums 'MDF' . That will give you access to a wide selection of discussions about all kinds of cleaning/preservation methods.
The 'cleaning finds' sub-forum:
https://www.metaldetectingforum.co.uk/viewforum.php?f=122

As you specifically asked about copper-alloy items, one of my own 'discoveries' for cleaning bronze items involves stiff bristle brushes.
I'll re-post here:

I've discovered a way of cleaning up bronze coins/artefacts with pleasing results, that I've not seen mentioned anywhere else, so I thought I would share it.

The patina on bronze items is often quite fragile, and you can see time and again forum posts related to this. Many mentions of washing a coin and losing all the detail, the patina going dull and rough. Comments from experienced folks saying they never get finds wet, and use minimal cleaning, such as wiping the bulk of the soil off, leaving it in the detail of the coin.

Despite the fact that the item has been in wet soil for centuries, I too think that fully drying it, then cleaning it, is the way to proceed. And with the right tools, the results can be very good.

Amongst my box of random tools, I have some well-worn artists stencil brushes. These have a lot of densely-packed short stiff bristles, usually hog bristle. I used one to brush off the dried dirt from a coin, and it was very effective, but it didn't damage the underlying patina. After more brushing, the patina started to take on a noticeable shine, as it was obviously being slightly abraded by the rough bristles. When I'd finished, the coin had an attractive darkened shiny look, and a gentle rub on a cotton cloth ( ie. my t-shirt ) finished it off. It wasn't as glossy as a waxed item, and of course no oils/waxes are involved, so it's better from a preservation viewpoint.

I've attached a picture of my brush, the bristles are very short, about 4mm , and the brush diameter is 8mm. I've had a scour of the internet, and similar brushes are available on eBay and Amazon (and your local art supply shop may have them too ).
Search for:
stencil brush hog
stencil brush bristle
stencil brush Jakar

Many of these brushes are huge, you need to find the small 8mm or "Size 1" ones. Priced around £3.00.

They have longer bristles than my worn ones. Try them as they come, but consider trimming them with a very sharp knife to get the stiffness. They will eventually wear short, but I've successfully trimmed off 3mm from the end of the aluminium ferrule with a Junior hacksaw to give new life to one of mine, so you should be able to get good value out of one.
Do the brushing in a well-ventilated area, as clouds of soil dust are generated.

Attached photo of a pretty Tudor hooked fastener that's been cleaned this way. There's a few harder deposits in the details that the brush didn't move, I need to carefuly have a go at them with a pointy tool, then re-brush them.

To summarise:
if you've dug a bronze item that may have a good patina, remove the loose dirt, wrap it in tissue and put it in your 'finds pot'. Let it dry out for several days at home so the patina is hard, then clean and shine it with a stencil brush.

Brush_7537c.jpg

Hook_7543c.jpg

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1 hour ago, Tom Slick said:

Brian- I'd put that coin Cookie/Phoenix button in some Hydrogen Peroxide and nuke it in the microwave. On bronze, brass, copper coins it causes them to fizz like an alka seltzer and pushes the crud off without damaging the coin. shallow dish with just enough HP to cover the button. Zap for about 30 seconds or until the HP boils. Let it sit for about 10 minutes and zap again. Al long as there is no metal exposed you can zap it as many times as necessary. A tooth brush between zaps will help. 

And:  Tom slick means to "zap" the petri dish of hydrogen peroxide in the microwave to just-bring-it to a boil.   Remove the petri dish from micro-wave, and drop the button in.  

 

He did not mean to put the button in to the microwave and turn on the microwave 🙂

 

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Brian, I got to 8:40 in the video, and then yelled at my computer screen !

 

You had me in suspense for 2.5 days now, waiting for the reveal.   Haha

 

Congratz dude !  3 PB's in a single hunt.   If it were me, I'd work on it further to coax the # off of it.  But I understand and respect if you want to leave it "good enough".  Like Bodie:  In an "arrested state of decay" haha

 

Nice going !

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Here's an article from 2012 Western and Eastern Treasures magazine on cleaning buttons:

http://archive.wetreasures.com/feature/201202.htm

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Sergei in NY has a website with some lengthy cleaning guides. There's plenty of choices, that's for sure.

https://www.metaldetectingworld.com/cleaning_preservation_coin.shtml

There's also an iron electrolysis guide, as I know some of you US guys dig iron relics:

http://www.metaldetectingworld.com/electrolysis_rust_removal.shtml

Another iron electrolysis guide, 'Andy's Patch':

https://qsl.net/2e0waw/rust.htm

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I've just read the 'Western & Eastern' article, and their opinion about tombac buttons:

The only way to clean these up is mechanical cleaning, any acid etc technique will destroy them.

I found that extremely fine grade abrasive paper, like silicon carbide, wet'n'dry, will remove dark stains, green deposits etc, whilst only slowly attacking the grey patina. Don't use anything coarser than 800 grade. Use 1000 or 1200 grade, and finish off with 1200, followed by rubbing with plain white paper and a buffing on an old cotton rag.

( '1200 grade'  means 1200 grains-per-inch, possibly in different countries there are different labelling systems ).

 

 

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Tom, I found that as long as the "find" is totally submerged in the Peroxide, it can be safely zapped over and over without having to remove it from the microwave. You just can't have exposed metal in the microwave. This makes the operation much quicker. 

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37 minutes ago, Tom Slick said:

Tom, I found that as long as the "find" is totally submerged in the Peroxide, it can be safely zapped over and over without having to remove it from the microwave. You just can't have exposed metal in the microwave. This makes the operation much quicker. 

ahh, ok.  I always heard the "urban legend" to never have metal inside the microwave oven.   I didn't know that metal inside a liquid is a different scenario.   Very interesting.  Thanx ! 

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1 hour ago, Tom_in_CA said:

I didn't know that metal inside a liquid is a different scenario.

Probably not just any liquid.  Water absorbs the microwaves, causing the water molecules to vibrate and that means heating.  For a liquid which doesn't absorb microwaves very well -- I would think a metal in that is to be avoided.

Hydrogen peroxide as it's sold at the drugstore is only a few percent H2O2 (3-5% I think) with the rest being water.

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That was the nicest pebble I've ever seen.  Now I do have issue with his comment about never finding them pebbles anywhere except the bottom of the ocean. 

Either way, very interesting video. 

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On 12/24/2021 at 7:03 AM, Tom Slick said:

Tom, I found that as long as the "find" is totally submerged in the Peroxide, it can be safely zapped over and over without having to remove it from the microwave. You just can't have exposed metal in the microwave. This makes the operation much quicker. 

I wonder if this would've worked better on my Phoenix button "cookie" experiment then Naval Jelly 🤔

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