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Cleaning Coin Finds -- An Incomplete Overview (long)


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One of the most controversial topics in metal detecting and coin collecting is that of cleaning coins. A lot of this comes from failure to define terms, such as purpose of cleaning and what ‘cleaning’

I would like to know what methods the experts use and how they considered experts. From my own experience if the patina is too thing the coin is junk anyways as there is nothing left below. I have tri

Great post. Here are those prior cleaning and selling threads. I love my tag system!

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I would like to know what methods the experts use and how they considered experts. From my own experience if the patina is too thing the coin is junk anyways as there is nothing left below. I have tried on clad different techniques to at the minimum to see what details are left below the crud and still keep the patina if that is in existence. I found that:

Acetone works well on tar and pine pitch.

Mild acids, pickling solutions are just too aggressive, including lemon juice etc.

Soaking in olive oil for long periods of time doesn't seem to do anything.

Even tried a 35 watt Co2 laser which burned the foreign matter into the surface of copper. (not reocommended)

Reverse electrolysis tends to destroy coins unless the surface has no dirt masking it (not recommended)

Baking soda and water will take majority of dirt off and gently when used with a soft electric toothbrush but just takes some time but will leave copper/copper alloys dull.

Typically I have been using baking soda and water to just take the minimal amount off so I can read what I have.

Lastly as a non numismatist I have my own 3 level coin grading system:

A- Shiny looks new

B- Readable looks used

C- Looks like an electrical box slug

Awesome post as usual, looking forward to your tests.

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58 minutes ago, kac said:

Even tried a 35 watt Co2 laser which burned the foreign matter into the surface of copper. (not reocommended)

Pardon my reaction, but that sounds like one of those "glad I didn't try that!"  😂  However, you show we have a lot of chances to experiment. 

Most of my coin finds aren't worth more than face value, and most of the remaining have bullion value only.  I have found between 150 and 200 Wheat pennies and most are pretty unsightly.   But I've also found a few Memorials with the same problems.  Thus I'm going to do the expermintation on the Memorials and save the Wheats until I've found/perfected a method.  Same goes with US nickels -- experiment with the trashiest late date Jeffersons before touching any decent date Jeffersons, let alone the Buffalo, Liberty (V-) and Shield varieties.  As far as (90%) silver coins go, I only have a few which need work.  It's mostly the water recoveries (and from what I've seen on this site, a few desert recoveries) that show problems with US silver coins.  But I'll be willing to experiment if someone wants to send me one or two.  (I'll return them, if there's anything left when I'm done in Dr. Frankenstein's lab.  😁)

 

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I've ruined ( removed the detail) from a good many old copper coins just by using water and a toothbrush, I learned not to use water the hard way. I've found that the way to keep the most detail is dry cleaning with a toothbrush and toothpick to remove the dirt. Wheats I just hit with a brass bristled brush because they aren't going to be worth much, and I just want them to look decent. Silver I just rinse off with water. 

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If you have naptha (rubber mold solvent/rubber cement thinner), it will do ok on copper to take some the dirt off without changing the color. Goof-off is nasty and think it is similar to the dangerous MEK used in counter top laminates and acetone is the safer alternative which also isn't very nice. For many years I had used acetone and it does quite a bit of nerve damage to your hands so snag some poly gloves like the ones used in hair salons.

An ultrasonic cleaner can do ok to take some the small dirt off without abrasives but avoid detergents as they can cause more patina on the coins. I had used it with a uv ink cleaner called yellow magic but you need to rinse really well after.

I just leave the patina on the coins now, butchered a few slugs thinking I could recover what is underneath but found for the most part the patina is in better shape than the badly corroded copper below it so removing that you remove the detail.

For my clad I have put about 30lbs or so through my vibratory tumbler in dry fine walnut shell which took the dirt off really well but took a few hours. Figured the bank might not appreciate me tossing muddy coins through their machines if I decide to cash them in LOL. I wouldnt use the tumbler on the oldies though because it is abrasive.

I should contact my uncle on this as he is a retired chemist and one point specialized in cleaners. Maybe he has a few tips.

 

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10 minutes ago, kac said:

If you have naptha (rubber mold solvent/rubber cement thinner)...

Naptha can be bought at hardware stores.  It's similar to the hydrocarbons in gasoline, but gasoline also has other additives as most know.  Hexane is a purer form but otherwise similar.  If your remember, or even still have, cigarette ligher fuel (Ronsonol in the blue and yellow small rectangular can is a common brand), that is also just naptha.  So is 'White gas' or Coleman Lantern fuel.

 

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I like to put them on the railroad tracks!! Or just wack them hard several times with a plain ol' 16 oz claw hammer with a smooth face! Really makes them coins shine!   

(Gotcha!!)😜

I usually put my finds in a pouch until i get home to clean! No rubbing in the field for the most part!

Dry land coins usually get a gross decon rinse, than anything decent gets a heated 3% peroxide bath till fairly clean, with toothpick cleaning and repeat, if necessary! 

Salt water/beach coins same gross decon, than heated white vinegar bath! Toothpick, repeat if necessary!

**Copper, clad, and silver get seperate baths!

**I'm not a fan of muriatic acid due to its hazardous fumes (lungs), and tissue damage (eyes, and skin) It's not worth the risk!!!

******Keeping in mind that these are detected coins from my particular area, and generally are not very old or valuable! ******And once a year i feed them into a coinstar machine to cash them in! The machine spits out the coins it doesn't like! 💰💰

With 1715 wreck coins, and oldies being the exceptions! Of course!!🤯

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I think the cleaning of a coin is subject to its rarity and or value.  I've personally (when I was younger) removed great detail of patina from a few Large Cents and 1 Flying Eagle.  All I used was water and a soft toothbrush.  So now for some of my coppers that I really like, it is a soft dry toothbrush and toothpick, as Kac does.

I've dug thousands of wheat backs and most are common dates/mint marks.  I toss then in a tumbler with fish aquarium gravel, a little water, squirt of Dawn dish soak and let them run 15 to 20 minutes.  All I am doing is knocking the crud and dirt off them.  

Silver,  When I was young they were tossed into the tumbler too and boy do they shine.  Problem is some silvers are semi and key dates with low mintages.  Those need to pampered and soaking in water with a light rinse is all I do.  Common Roos, Merc's and Washington quarters are soaked and brushed with toothbrush, but I quit tumbling them, as the shine, in my opinion is not recommended.

Nickels,  Those pesky dark stained, sometimes purple or red, brown, even black on occasion.  If they are common dates, I toss them in the tumbler.  Semi dates ones get the water and soft tooth brush.  I'll use an eraser on them to add highlights, but I assure you there is abrasive marks left from the eraser.  At least the common Buff or V now looks better with a highlight, but that is my coin so I am not worried of value.

My 1913-S Barber Quarter (Key date) was dug in Nevada and as most of my 100+ yrs old silvers coming from the desert with high alkali, they come out of the dirt with a crustry gray coating.  I have not done anything with it, other than water and tap dry.  The actual condition of the coin is F-12 with detail, but the other blemishes and clap on it kills the value and most certainly drops condition.

I have yet to decide (and keep going back and forth) on if I should get it professionally cleaned and as stated what makes one a Professional?  I guess it depends on the person and what you plan on doing with it.  Myself for this coin.  If PCSG says cleaning will drastically reduce the value, then I'll probably leave it as is.  If they say "after cleaning it will have detail of F-12" and look much better, but will be labeled as "Environmental Damage", and the value will drop a little, then I'll probably get it cleaned.  If the value drops 50% or more, I might as well leave it as is.  Who knows, but right now it looks like crap to me.

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I have found out that an equal part of washing soda and baking soda mixed with distilled water will clean copper pennies very well.

I have a few that I am going to be cleaning soon so that I can get them framed and hung on the wall.

 

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