Why You Should Never Clean Your Coins
Some newcomers tend to quickly assemble an expensive collection and bargain at auctions. But in fact, they may not know the basic knowledge that there is no need to scrub the coin before using coin identification, and there is a reason for this.
The Psychology of a Collector
Understanding the ban on cleaning, we need to understand the people buying coins called numismatists.
For a normal person, "new" and "clean" are words meaning "good," so we wash clothes and polish furniture thinking a clean object costs more than a dirty one.
But for a collector, a coin is not just a piece of metal but a historical document witnessing an era having the main value in the coin being original and authentic.
A coin living for 100 or 200 years inevitably changes because the metal reacting with air and water creates a layer of oxides called patina.
For you, patina looks like dirt, but for a collector, patina is:
Making a fake patina perfectly is impossible, so a coin having a smooth and old patina is a real coin not being a modern copy
Patina is the "skin" of the coin keeping the metal safe and preserving the coin protecting it from destruction
A noble patina having gold or rainbow colors gives the coin volume and beauty valued higher than an artificial shine
Destroying the patina, you destroy the history turning an antique into a simple piece of shiny metal.
What is Mint Luster and Why You Cannot Return It
The most important concept needing understanding is mint luster.
Making a coin at the factory, a heavy steel press hits the metal with great power making the metal flow filling the picture. At this moment, microscopic lines appear on the surface going from the center to the edges like sun rays reflecting the light in a special way being very small.
Taking a new coin from the bank and turning it under a lamp, you see a "ray" of light running like a spinning wheel being a mint luster.
Why is this important? Mint luster is the main sign showing the coin condition being very fragile.
Starting to clean the coin:
Using an abrasive, you physically erase these microscopic lines scratching the surface, so the coin starts shining, but this is a dead shine of polished metal looking terrible to a collector
Using chemicals, you dissolve the top layer of metal containing these lines making the surface dull or unnaturally glossy
Remember this rule: Restoring mint luster is impossible because having erased it with a cloth or dissolved it in acid, you lost it forever meaning the coin becomes damaged forever.
Types of Cleaning and How They Kill the Coin
Abrasives
Like soda, toothpaste, sand, kitchen powder, hard sponges, and erasers.
Abrasives are hard particles acting like sandpaper, so rubbing the coin with them, you remove the dirt, but removing the dirt, you also remove the top layer of metal. Looking under a microscope, you see a coin looking like an ice rink after a hockey game covered with thousands of small scratches.
Acids
Including lemon acid, vinegar, cola, kefir, and toilet cleaners.
What happens: The acid does not know the difference between dirt and metal reacting with the oxides.
Copper often has a beautiful brown patina, so putting a copper coin in acid, you destroy the patina making the coin pink like a pig looking like a piece of raw meat. Later it will turn dark again, but these will be ugly spots, and the acid eating the copper makes holes making the surface porous like a sponge
Silver becomes black with time, so acid removing the black color makes the surface dead white having no depth making the coin look like an aluminum token
Electrolysis
This is connecting electricity to the coin in salt water.
What happens: This is the most barbaric method for a beginner because electrolysis literally tears particles of dirt and oxides from the metal surface often making pieces of the coin fall off together with the oxides. In the end, you get an object looking like the moon surface covered in craters and holes having an unnatural look.
How Much Money Do You Lose?
There is a scale evaluating coins from 1 to 70.
Fine (F) or Very Fine (VF) is a coin used in circulation being worn.
Uncirculated (UNC) or Mint State (MS) is a coin not used in circulation having full mint luster.
The price difference between these states can be huge.
Being in perfect condition and having native patina and mint luster (MS63), a token can cost $500.
Thinking it is too dark, you clean it with soda making it shine but also making micro-scratches
Now its condition is not MS63 but "UNC Details - Improperly Cleaned."
Its price instantly falls to $50-70.
You just erased $400 with your own hands simply rubbing the coin with a sponge.
Talking about rare coins, losses can be thousands of dollars because there are cases of people finding rarities costing 20-30 thousand dollars, cleaning them to a shine, and seeing auction houses refusing to sell them — but in any case, find out the individual characteristics of your token through any free coin identifier app like Coin ID Scanner or Coinscope.
When Is Cleaning Okay?
Finding a coin in the field, you see it covered with a thick layer of earth and clay, so in this case, you need to wash it using only water and soap, not rubbing it.
Just soaking it in distilled water, you wash away the soft dirt using a soft brush, so seeing dirt not coming off, do not pick it with a nail.
Keeping a coin in a cheap plastic album, you might see a green sticky film from PVC destroying the metal, so you need to wash it off using pure acetone being the best way. Acetone dissolves organics being absolutely safe for metal and patina.
Important: Acetone is the only chemical considered safe by collectors for removing organic dirt because it does not react with metal. But even using it requires skill because rubbing the coin with a cotton pad soaked in acetone is forbidden, so you can only bathe the coin in acetone.
Professional Grading and Restoration
There are companies like NGC or PCGS doing grading and evaluating coins.
These companies have departments doing professional conservation, so having an expensive coin with ugly spots, you can send it to them.
Chemists working there restore coins not scrubbing them with soda but using complex chemical solutions and microscopes removing only the spot, spoiling the look and not touching the rest.
This costs money, but it is the only way to improve the look of an expensive coin without killing its value because repeating this at home is impossible.
What To Do If You Want To Clean?
Take your hands away and put the soda back.
The only safe method is warm running water and simple baby soap, so washing the coin gently with fingers without sponges helps to wash away dust and fat.
Seeing sticky stuff, tape, or fat on the coin, soak it in pure acetone because acetone not removing patina and not returning shine removes organic dirt.
