A New Coin Cleaning Project. 1803 Large Cent

This is a great thread! Thanks for taking the time to photograph the progress and share the details with us!

Looking forward to see how this one turns out!

Some months ago, I did some Google research on verdigris passivation and removal for copper and bronze object generally, not specifically on coins. At least some of the information most probably would be relevant to the subject coin in this thread.

some process pics. there are some unexpected things happening here. so far all I have done is let it soak in xylene and wash it off using dawn dish soap and tap water. ive washed it several times. I use my hands to work the soap in. gentle. work vertically. no scrubbing.

tuesday afternoon



thursday evening



you can read the last date digit! it is an 1803 S-251 R-2.

big chunks of the green and blue stuff have been flaking off of the surface.. the jar had lots of chunks floating around and I have dumped and replaced the chemicals. that stuff can scratch copper so its important to keep it from sliding across the surface.

there are at least 3 different things happening. there is a blue powdery substance, a green crystalline substance and the glue. the glue is amost entirely dissolved with the exception of the area near the B in liBerty.

there was probably something on the surface of the coin below the verdigris/cuprous oxide/bronze disease/ whatever. I dont know whats on the coin and I'm not a chemist so I prefer to use terms like gunk rather than using a more precise word that may be inaccurate.

the color washed right off the surface with soap. now its somewhere between pink and a pumpkin color. nothing I have done would have taken off natural toning. something else was on the surface. it sure gave it a nice brown color. I'm not sure what was on the surface. looks like we will be doing some retoning on this coin.

im going to leave it sitting on the porch overnight and see what happens with the color. ill take before and after pictures. it should be in the mid 30's - upper 40's (2c-7c) 40-50% humidity.

total time ~15 minutes

happy thanksgiving everyone!

i didnt. that was a mistake. dellars was what I thought of as well.

for those who havent encountered the product Dellers Darkener is basically sulfur powder in vaseline. its a tool for recoloring copper coins. I dont have much experience using it but in the right hands it can produce some really nice results. I think I have a container of it around somewhere. ill track it down and take a picture to show everyone.

here are before and after pics of a night sitting outside. I did this because I wanted to demonstrate how reactive copper is. I also wanted to see how active out various problems are.

early on in learning to conserve coins I set about exploring how reactive parts of my home were. I put a bunch of mint red 1970s cents all over the place and watched what happened. the desk is different from the shelf in the kitchen which is different from the back porch. each can be useful and a better understanding of how copper oxidizes will help you to better store your coins long term.




as you can see the copper is pretty raw and changes color quite rapidly. the reactions are active. you can see a bit of a greenish hue to the fields in front of libertys nose. we will need to neutralize that stuff before we are finished with this coin or the coin will revert to a problematic state.

one of the more common houshold methods of treating this stuff is sodium bicarbonate. baking soda is ideal for killing that reaction but it is also corse and abrasive. many wheat cents have been polished to a high shine by rubbing them with baking soda. we will eventually be soaking this coin in a weak sodium bicarb and water mixture. there are some other things to do first.

before I do that I want to get rid of the big chunks of debris on the surface. I'm going to pop it under the microscope and poke some of that stuff off the coin. this part requires a lot of patience and steady hands. its important to stay in the moment and only work if you can stay focused.

here are some of the tools and chemicals I have on hand.

starting in the upper left corner and movong clockwise we have:
dellers darkener - for recoloring coins
bu plus - residue removal
care - a surface treatment similar to blue ribbon
conserv - a proprietary solvent mixture
hypodermic needle - great for getting into the really tiny spots like around the leaves - can scratch copper
dental tool - good for hard and large chunks. excellent grip. can scratch copper
engraving tool - comes with a variety of tips. good for large hard chunks - made specifically for moving metal and to be used with extreme caution
rose thorns - excellent for removal of all sorts of things. when fresh cut they are pliable and soft enough that they will not scratch copper. this is the place to start if you havent done manual crud removal before.
cotton swaps - good for applying chemicals. wont scratch copper on their own but can damage it by collecting pieces of debris.

the last picture is my stereo microscope. I do all of the work at 60X magnification. if it looks good at 60X its going to look great at 7x-10x (most loops) or in hand.



you'll notice that I have a bunch of the manual tools labeled as - can scratch copper - some of the things you run into are harder than copper and you need something hard to remove them. these are the tools that take the longest to master and are the most likely to ruin your coins. if this is a skill you wish to learn I highly recommend practicing on something cheap and common with a similar metal content to what you plan to work on. be confident you can address the issue without damaging the coin before you start the project.

the goal is to remove the contaminants and neutralize the reactions without disturbing the original metal. if I do that correctly the coin will look better and be better preserved moving into the future.

not really any extra time here. sill ~15 minutes. the next part is where the time starts to add up.

thanks windmiller! here is what it looks like today. its starting to looks quite a bit better. going to need some more work on the back. the front is looking pretty good. just a couple spots near the but tip/ 3 in the date and around the B in liBerty.

i have been alternating between poking at stuff, solvents and soap. I also handle it and touch the surfaces a lot. if you want to turn bright copper brown I think the best way to to do it is naturally. hands, air and time. its how all the nice brown coins got that way in the first place.




total time is ~1hr now. I fiddle with it while watching movies/tv sometimes and dont really count that time.

thanks jbuck! I'm pretty pleased with how its going so far. once that glue came off the obverse really started to look something like a respectable coin.