How can concentrated Hydrochloric acid be used to clean copper coins?

  • Thread starter Thread starter DaveC426913
  • Start date Start date
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
18 replies · 9K views
DaveC426913
Gold Member
2025 Award
Messages
24,696
Reaction score
9,099
I just dug this up out of my front lawn. It is a 1920 Canadian penny. (Our house was built in the 20s.)

I'd like to

a] get an idea of any value it might have just for fun (it's likely worth <$1.00). I've looked on a couple of sites. Apaarently the 'DEI GRA' is significant.

b] clean it up. I've tried Brasso, but little luck. I've tried peroxide but little luck. Next, I'm thinking of trying C-L-R. Any ideas?


Coin collectors have any advice?
 
Attachments
  • penny.jpg
    penny.jpg
    32.3 KB · Views: 541
Chemistry news on Phys.org

Discussion

Or Cillit Bang! On the advert Barry Scott cleans up an old penny, look how shiny it gets!
 
Don't get your hopes up. If it's 1920, the head is of King George the fifth. The writing around the obverse side is "GEORGIVS V DEI GRA REX ET IND IMP" . This is latin (and abbreviated too) for "George the fifth by the grace of God King and Emperor of India." That was his title. I've got a 1916 penny and it's worth about $4 in "very fine" condition. These were made of soft copper (not alloyed with anything) and they wore down and corroded quickly. If the surface is pitted, then it's not worth much at all. It's going to be worth much more to you personally just for the story behind it.
 
A penny for your thoughts Chi...just my two cents.
 
Two Cents? I'll tell you about two cents! I got the coin collecting bug about 35 years ago from my grandmother who had lots of neat coins including an X. fine (almost uncirculated) US two cent piece. She died about ten years ago and left her coins to me. THis coin, plus many other valuable coins, she had taken and DRILLED HOLES into them so she could put them on a necklace! There was about -$2000 dollars worth of HOLES on that necklace!

And it's not like I could get MAD at her. RIP.
 
DaveC426913 said:
b] clean it up. I've tried Brasso, but little luck. I've tried peroxide but little luck. Next, I'm thinking of trying C-L-R. Any ideas??
Generally, it is a bad idea to try to clean up any coin which you think might have some value besides the obvious face value. Coin collectors like the coin to be in its natural state, not artificially enhanced, no matter how bad it looks.
Having a brand new looking 1920 penny is probably less desirable than having an old, ugly, looking one. I would not try to do anything too severe in attempts to clean it if, indeed, it has value (it probably does not though).
 
Last edited:
Just been looking in my coin collectors book and your coin is worth a
$ioo,ooo,ooo in mint condition, but 2 cents in the condition yours is in.
 
wolram said:
...your coin is worth a $ioo,ooo,ooo...

Well, if it's worth an imaginary amount of money, then I'll just have to imagine it, won't I? :biggrin: :biggrin:
 
One day i was out with dad metal detecting in field behind a church, suddenly we were getting hit after hit but the coins were all from other countries, we must have dug up a hundred, for some time we wondered how the heck they got there, ages later we found out that they were coins put in the church collection and the vicar of the time lobed them over the wall into the field.
 
Yeah, they aren't worth anything.

The year 1920 is nothing special for the Canadian cents. It's worth about a dollar just like you said, but now that you cleaned it, it's probably worth like 25 cents or less.

By looking at your pictures, I would guess the grade to be FINE. The FINE grade is listed at 50 cents, and after cleaning, it's usually about 1/5 of the price. You knocked it down to like 10 cents.

I collect Canadian cents, and I would never buy a cleaned cent. The only way I'd buy one is if I need to fill a hole and it is really expensive, but even then I won't. I never bought one yet, so I don't know how I would. They just look ugly afterwards.

On the other hand, if you got a 1923...

...but cleaning it would have destroyed it.

Note: A collector can tell if it has been cleaned.
 
Oh well. My fortune lost.

BTW, thanks Brewnog, the overnight vinegar bath did an excellent job. Now I'm alternating between vinegar and Brasso, and it's coming quite clean.

Next time maybe rather than cleaning the whole thing, I'll just clean the 4 digit year and leave the rest in its 'beoldened' state.
 
Jason Rox said:
Note: A collector can tell if it has been cleaned.
Won't be hard with this one. He'll get a hankering for fish & chips, is my guess.

I didn't have any white vinegar around so I used malt instead...
 
Whenever I want to clean Copper and clean it FAST, I use my good friend, concentrated Hydrochloric acid...12.50 Molar.
If all goes as planned, you will have one clean penny...if something goes wrong, you won’t have much of a penny at all left to speak of.

I once tried to clean a penny I had which was black, caked with all sorts of stuff, so much so you could not see the design on the coin. A few drops of HCl later, I learned a valuable (well, I really wouldn’t call it valuable...it only cost me a cent) lesson, if there is even the slightest chance some of the Copper coating is missing, don’t clean with concentrated HCl. A good portion of the Zinc reacted with the HCl, making the penny even uglier than before.