Hardcore Ancient Cleaning

So I ordered several pounds of ancient coins a couple of years ago. I have tried every recommended cleaning method with varying levels of success. I had a group that no matter what I did I couldn't penetrate the shell. So I decided to experiment... and I think I may have stumbled onto something.

Here is the lot that I could never get clean. keep in mind some of these coins soaked in oil for over a year.



I chose this piece for demonstration purposes:



The first step... and this is going to sound crazy... was to heat and cool this piece several times carefully with a blowtorch... I theorized that this would help release the verdigris from the surface of the coin by expanding and contracting the metal. The coin was then placed in a bath of sodium hydroxide and water for several minutes.

This is the product after that. The verdigris is noticeably loosened.




A little CAREFUL picking with a metal pick and brushing with a plastic bristled brush....



This is a coin that normally would be discarded as I literally tried everything I could think of to get it cleaned. The final result.

 

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Overall cleaning time... about 5-7 minutes.

 

Awesome. I'm guessing the patina came off which is the #1 no-no when cleaning coins...but as far as I know no one has come up with a way to get the gunk off without destroying the patina as well on the really tough ones...

If so you better patent your blowtorch method

I did a lot of reading on cleaning a year or so ago...more than I did cleaning as it can be very frustrating. The opinions are split on this, but I say if you can end up with something when you have tried everything else, a patinaless coin is better than a rock.

 

Yeah that was my thought.... these were toss outs anyways... so anything is better then nothing.

 

Supposedly electrolysis is another option that probably does the same thing. Not sure if it is more or less effective, at least timewise per coin. Clearly you got all the junk off

Do you feel good or bad when you actually apply very hot fire to a coin?

 

Actually, you can use distilled water or olive oil and use a dental pick or safety pin and not remove the patina at all. Of course you have to be careful.

On those that do get the patina remove, sometimes the metal underneath is not solid or porous and looks like crap. You got lucky with that particular coin.

 

These particular pieces soaked for over one year in oil. I then picked at them with a toothpick and had no luck. That is how the vast majority of the coins cleaned up. These coins were the ones that would not clean.

 

Your example came out much better than I would have thought. When I first started collecting Ancients, I got into the "uncleaned lots" hoping to find something of value for my collection. I never did. However, like you, I had some coins that were just too stubborn and I resorted to electrolysis. Big mistake. It cleaned the coins to the point they looked like brand new penny's. Like I said, your results don't look near as bad. BTW, any idea as to the ID of the coin? I don't recognize it.

 

I mentioned the freeze/thaw technique and was advised that it could crack some coins. A variation on this would be to chill the coins with dry ice and then put them in boiling water.

 

I have tried the blow torch method before........its not a new technique (sorry LD)
You have to be careful because the lead present in many bronze coins melts out at a much lower temperature than the other metals would, which causes the coin to fizz and it gets covered in lots of tiny shiny lead droplets. When these are rubbed off the coin is pitted where the lead has left small holes. I have not used the method since.......

 

I have a blow torch and liquid nitrogen at work. I should buy some uncleaned ancients and try this.

 

It's a prutah. My gut says Hasmonean, Alexander Jannaeus, but I can't make out enough of the lettering.

 

Do NOT get them off Ebay.

 

I would think, use the liquid nitrogen but skip the blowtorch, let the coin return to room temperature naturally. And try this repeatedly until the verdigris cracks off. A blowtorch probably creates more compounds on the surface of the coin.

 

Not a bad result...at least you didn't use a rock tumbler.

 

I would be concerned that liquid nitrogen would result in a broken coin (or flying shrapnel?) when combined with the blowtorch. I'd start with one or the other and not go ballistic until the lesser methods failed. The blowtorch alone seems safer and more likely to work. I did try a torch years ago but did not find anything I wanted under the crud.

 

As mentioned in another thread, I tried heating a couple of dirties last year. It did help with some of the crud but with one I overheated and several little blobs of molten metal burst forth and rolled right off the coin. Must've been lead.

Might be safer heating in an oven or kiln, although whether it is a good idea is up for debate. If the coin is unsalvageable by any other means, I suppose you don't have much to lose though. In the cases of my heated coins, there was nothing worth finding under the corrosion and crud.

 

Yeah, I have had that happen. It's a learning curve... you want to get them hot... but not too hot.

 

Liquid nitrogen is fun, but be careful. I have seen people dip a graham cracker in LN2 (liquid nitrogen) and then put it in their mouth...smoke shoots out your nose. Treating the coins in LN2 and then dropping them into water, either room temp, hot or boiling should be more than enough.

 

i'm shocked you found anything under that...i would have thrown that one straight in the cull bag. i'm impressed LD.

i think if i put a coin in the soak for a year, i would just forget i had it.