How do I clean the dirt and scum from this letter?

I have not had a sharp tooth pick or rose thorn scratch a coin. I HAVE HAD A SHARP TOOTHPICK SCRATCH A COIN (bright copper colored hairline) when it became contaminated by the debris particles I was trying to remove. One tip is to ALWAYS work with a wet surface unless it is the green scum on copper but that comes right off with chemicals such as acetone.

 

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Try soaking in distilled water enough to allow the water to penetrate the dirt. Then place the wet coin in the freezer allowing ice to form thus breaking the dirt off the surface of the coin.

 

very popular in the 50s,60s,and 70s, a soft fine animal hair bristled jewelers brush.

a good long soak in acetone, or distilled water, whatever you want or are more comfortable with, in order to soften up the gunk and then a light gentle brushing with this very specific brush type. no nylon, no cotton, no fabric, no metal bristles, or wood, Animal hair bristled jeweler's brush. don't brush too hard or too much, just a light brushing, a couple of times tops.

any other brush material or cloth is going to be some sort of polymer or even cotton, it's mostly cellulose, which is used to make polymers.

The old timers that collect early coppers and are attempting to preserve them as best as possible, swear by a hair bristled brush and mineral oil and only that in order to clean up verdigris on them and preserve their coins.

Do not use tap water which may have a high or low pH but WILL have chlorine or fluoride.

I'd go this type of route if I were in your position. I wouldn't mess with wood and pick at things, just seem like it would work but possible to do more harm than good if you aren't sure of what you are doing.

give it a soak and a couple gentle swipes on the brush and give it a rest then try again, eventually it will get knocked off and not damage the surfaces and further than they already are.

 

Thanks, guesses and suggestions are nice. Have you ever done this? I just ended up with frozen dirt - some of which came off with hot a hot water rinse. So far, it seems the toothpick, rose thorn, and ultrasonic are known to work

 

Try a sonic cleaner. Harbor Freight sells them. I use it on all metals. It cleans most stuff without destroying the item. Do not clean gun parts with blueing.

 

Why, what happens?

 

I have had poor results using an ultrasonic. Somebody on CT or CU recently did an ultrasonic experiment and which yielded poor results as well. Don't forget, the coin can move around in the basket and rub against the hard plastic.

If you use an acetone soak, I would make sure the acetone DOES NOT evaporate and you keep it sealed in a dark place (and if it's sealed and stored in a warmer place, make sure pressure doesn't build up. Probably not very likely, but something to consider). The (infamous?) Stony Brook University research paper showed that when the acetone is in the presence of light AND evaporates, acetic acid may form on copper surfaces. I prefer using multiple short soaks instead of a long one.

 

Oh, I'd never use a basket. Tongs, or maybe a soft net.

 

I’ve tried on IHC’s. It did help (but not fully remove) on a few of them. I used coins that had nothing to loose. I tried it to test, learn, practice. It works best when the “crud” is caked dirt. Repeated attempts where necessary to make a difference. I’ll assume the hot water was used after the freezer. Did you try repeating the process? I think think a longer soak before freezing and repetition would make for better results. I was attracted to the process because it seemed non destructive to the coin. The problem is with what the crud did to coin prior to removal attempts.

 

I suggest that folks NEVER use a metal or plastic basket in an ultrasonic cleaner. Plastic tongs work very well and do not damage the coins edge. If your coin is not good enough to watch while you hold it...

Additionally, always agitate the coin while you are holding it in the ultrasonic solution. This prevents bubble damage to its surface. A coin can actually develop round depressions into its surface if an ultrasonic is misused.

 

Sorry, I'm still waiting for the other shoe to drop. I'm sure you, being the expert you are, knew and probably were going to try all of the suggestion, save the steel wool. So what are you looking for?

 

As mentioned above, anything you use to scrape or dig can scratch if only because of the material you are trying to remove. After a long soak in distilled water, or perhaps several soaks and rinses, you might try a strong squirt of water. I'm not talking high pressure sprayer here, but from a strong spray bottle or even water gun. My dad used to have a device called a "WaterPik" that used pulses of water to clean his teeth. Something like that might be useful. Just be careful the squirt doesn't cause you to drop the coin.

 

That someone was me. Here are the links to the results I posted. Note that I set things up to prevent most of the predictable problems. I also ran the coins in the cleaner for much, much longer (6 to 12 minutes) than anyone ever would because I literally wanted to see if I could damage the coins. I did damage the large cent but not the other coins.

15 to 30 seconds is about what I would recommend.

Ultrasonic Coin Cleaning, Part 2 | Coin Talk

 

For something like this, I would give a couple of 24-hour soaks in distilled water followed each time with a flowing water rinse...coin in sink on washcloth and hot water pouring over it for ~30 sec. or so. Acetone 24-hour soak, then back to a distilled water soak and MAYBE a soft toothbrush. Scratching is going to be caused by surface debris being scraped around...I'm hoping this is one of your test type questions and look forward to being educated.

 

I know almost nothing about coin/metal cleaning, but seeing these discussions about water makes me wonder if a waterpik be helpful for something like this? Even turned up full blast, it shouldn't scratch I wouldn't think...

 

ALWAYS begin conservation projects with distilled or deionized water. I've NEVER had an issue with water.

 

I have seen coins go bad with distilled water, but only doctored ones. The coin was a lie to begin with, and the chemicals came off in the soak. I do not blame the water for the damage, it only showed me the truth.

 

My son used it on a handgun and it removed the blueing.

 

I heard porcupine quills were good. read that here on CT, and have had 100 quills on my ebay watchlist ever since. Maybe I'll buy 'em one day and see.