Brasso and Silver polish are total no nos. It is best to clean them in non abrasive soap in hot tap water or preferrably distilled water.
For coins that are really tarnished and may have grit and oxidised adherence to them then here are some questions and suggestions for you to experiment - use old coins of no value.
- Do the coins become clean or do they remain tarnished or oxidized?
- Which cleaning solution works best?
- How much effort does it take?
- Do the copper pennies get cleaner than the other coins?
- Do the oxidized coins get cleaner than the tarnished coins?
- Six pennies (tarnished or oxidized)
- Six nickels (tarnished or oxidized)
- Six dimes (tarnished or oxidized)
- Six quarters (tarnished or oxidized)
- One cup dish liquid
- One cup lemon juice
- One cup orange juice
- One cup water
- One cup cola
- One cup baking soda paste (Mix baking soda with water for a paste consistency.)
- 24 cups
- Six plastic spoons
- Six toothbrushes
- Newspaper or art cloth (to cover the table)
- Latex gloves (optional)
- Fill four cups each one quarter full with each of the six cleaning solutions suggested (4 with lemon juice, 4 with orange juice, 4 with cola, 4 with water, 4 with baking soda paste and 4 with dish liquid). Label the cups.
- Carefully record each coin’s condition prior to placing it into its cup.
- Place one of each type of coin into each solution.
- Let all coins soak overnight.
- Using the plastic spoons and latex gloves, scoop each coin out of its cup and place it on the covered table. Take care to label and keep track of which coin came from which solution.
- Examine the coins and record what you see before you start using the toothbrushes.
- Use the toothbrushes to clean the coins, rinse with water, re-examine the coins, and record your observations.
- Address the research questions.
Here is another site plus its suggestions
- How to Clean Old Coins and Dirty Coins
If you do decide to clean your coins, there are various tried-but-true methods you can use. Never use jewellery cleaner or a metal polish, as these are quite harsh and will damage your coin. Always use a cloth or fabric on your coins, and not a tissue, paper towel, or other paper-based material – these can scratch the surface of your coin. And always start by washing your hands with soap and water, to remove any oil or grit from your fingers.
Run cold water over your coins** — You might want to start simply by holding the coins under the tap and running cold water over them This will start to knock away any dirt or grit that is encrusted on your coins. Faster-running water is more effective.
Soak your coins in warm soapy water** — Add a squirt of mild dishwashing detergent like Persil Washing Up Liquid to a plastic container filled with warm tap water. Rub each coin inside this soapy bath to work off any dirt or grit. Don’t put all your coins in here at once. Work on them individually, and do not use a metal or ceramic bowl, as this can also scratch your coins.
Use a toothpick or extra soft-bristled toothbrush to work off encrusted dirt** — Either of these, in combination with warm soapy water, can be useful to pick off dirt or corrosion stuck on your coins.
Soak dirtier coins in a cup of white vinegar** — The acid in vinegar is great at dissolving stubborn stains or corrosion. You can soak the coins for at least 30 minutes, a few hours, or even overnight.
Rinse under hot running water** — After soaking, make sure to rinse off any soap residue or vinegar with hot or warm running water. Take care not to scald yourself with the hot water.
A final rinse with distilled water adds shine** — Distilled water is free of any impurities or minerals, so it can rinse away any contaminants in tap water. One by one, swish each coin around in a plastic container filled with distilled water.
Pat or air-dry on a soft towel** – Do not rub your coins dry. Pat them dry to remove, and let the air do the rest. If the final rinse was with distilled water, just let them air-dry without any patting.
So long as you are aware of the effect on their collectible value, you can now clean your coins with any of these easy methods. With just a few simple steps, your can remove the dirt, grime, and germs from your coins and leave them looking shiny and new.
Here is how NOT to clean coins
How NOT To Clean Coins: Tips On Cleaning Coins
OK, as I always start every post I write about how to clean coins, I’m going to put this blanket statement out right now: I strongly urge anybody who wants to clean their coins to reconsider. Why? Because an improper cleaning can ruin a coin’s value, damage its surface, and deny future generations the chance to enjoy your coin in its wholly original form.
That being said, some people will still engage in cleaning coins anyway in an often ill-fated attempt to make it look brand new again.
While most posts usually tell you HOW to clean coins , I’d like to try something different: tell you how NOT to go about cleaning your coins. After all, there really is only one way to clean your coins safely, but unfortunately many of the popular methods seen online are actually detrimental to coins and could leave yours with only a fraction of their original collector value.
So, what ways shouldn’t you clean your coins? Here’s a debunking of some popular coin cleaning recommendations:
Why You Shouldn’t Clean Coins With Toothpaste – It Certainly Won’t Whiten Abraham Lincoln’s Teeth!
You’ve probably seen a few websites that suggest your coin’s pearls need to be a little whiter. However, you’d be better if you skip making your coins minty fresh. Toothpaste is a highly abrasive agent that will strip away more than just plaque – it could literally remove metal right from your coin. I used to experiment with rubbing toothpaste on some of my coins years ago, but I ended up ruining every coin I cleaned with it. Each victimized coin looked unusually shiny, and 5X magnification revealed countless tiny striations in the surface, rendering the coins almost worthless.
- Ketchup Isn’t How I Clean Coins Unless I Want To Eat Them Fried
Who doesn’t love a little ketchup with their French fries? Some people love ketchup so much they even put it on their coins… well, maybe not because ketchup makes coins taste any better, but because the shiny, red condiment can help remove grime, grease, and other surface adherents from coins. The highly acidic nature of ketchup helps lift away dirt and debris when gently rubbed onto coins. However, the acid can also wash away a coin’s patina, significantly lowering the value of the coin.
Baking Soda And Vinegar – Great For Science Fair Volcanoes But Not For Enhancing Your Coins’ Value
When I first began collecting coins and wanted to learn how to clean them, I learned that mixing baking soda and vinegar in a glass creates a highly potent solution that can strip away dirt and grime from coins. All that has to be done is to mix the baking soda and vinegar together (about 1 part baking soda and 4 parts vinegar is the ratio I always followed) in a bowl or glass then immerse the coins you want to clean; this mixture seems to work especially well on pennies. In fact, it works so well that, like the other coin cleaning brews, it can completely strip away the original patina and obliterate the value of the coin.
- Metal Polish Will Tarnish Your Coins’ Value
You can’t watch daytime TV without seeing at least one or two ads touting the latest and greatest silver or copper polish. Maybe you’ve even thought of buying some for yourself so you can shine your old coins right up! Well, perhaps you’ll want to save your $9.95 bottle of Shiny-O for your jewelry, pots, and pans, because all of the metal cleaners, dips, and polishes you’ve seen advertised on TV or on the shelves at your neighborhood big box store will ruin your coins’ surface patina. In some cases, these metal cleaners contain caustic chemicals that will permanently damage the coin.
How DO You Clean Coins, Then?
There’s only one method I recommend to anyone who wishes to [clean their coins], and that is to hold them under gently running tepid water for a few moments, then gingerly patting the coin dry with a soft cloth. What this does is wash away loose surface particles without damaging the coin’s delicate surfaces.
And, the beauty of cleaning a coin this way is that it really isn’t even considered “cleaning” at all, by most standards. That’s because a coin is usually only considered “cleaned” if it shows hairlines or other signs of damage consistent with an abrasive cleaning, such as would be caused by the methods explained earlier in this post
These were all from sites oninternet so easily researchable. My own suggestions are this and yes I am a coin collector.
When we detect old coins and they have a heavy patina and oxidization then you are NOT going to get rid of the patina or oxidation without completely destroying the value…IF it has any value. We often look at coin values and see a value such as $800 NZ for an 1856 British penny. That value is UNCIRCULATED - as new to an amateur. The coin you found though is heavily oxidized and worn. It is not even in ‘F’ for fair condition. Its value therefore may only be two ot three dollars maximum! How many of these so called British or American higher value coins according to year do you want? I can give you handfuls that I have detected? You see they are worth nothing more than curiosity value because they are heavily oxidised and worn and therefore have negligible collector value. I see many many coins that the guys on here have found and every now and again the condition of one or two is actually quite impressive and these ones are the ones worth keeping. As for the rest just clean the crud off and then put them into the treasure chest - or in my case into an old clay crock and forget them. Great gifts for kiddies who take an interest in them. Some kids will go gaa gaa when they are given that old coin you found not because it looks uncirculated but merely because of its age.