Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Cleaning Pennies
Q. Hi, I'm doing a project for my third grade science fair. I have to find out what juices clean pennies the best. What juices should I choose and why? Thank you.
Marissa P. [last name deleted for privacy by Editor]- Lancaster, New York,USA
2001
2001
A. Choose the juices you don't like to drink, Marissa; that way you'll run out of them and not have to drink them :-)
Sugar water will not dissolve anything, whereas sourness indicates a high acid content which is good for removing that brown oxidation, and saltiness indicates chloride which is also good. So salty and sour drinks are probably the best cleaners.
But "why" is actually a very complex question involving pH, chlorides, organic acids, chelators and complexers -- and even your teachers probably don't completely understand why one juice works better than others.
Conduct the experiment, accurately record the results without being swayed by any expectations, and you will have achieved a lot! The point is not actually to find a juice to clean pennies, but to learn how to conduct experiments. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Marissa you should use Lemon juice it works great. I use it in my 7th grade sci. project. Oh and you should use things you don't like because then you can just throw them away after. Pretty smart huh?
Whitney P [last name deleted for privacy by Editor]- Florida, USA
2001
Multiple threads merged: please forgive chronology errors :-)
In another thread you said that pennies are copper plated zinc these days. Well, I have one simple question. I am doing a report on the same thing as other writers (cleaning copper pennies) and I wanted to know what pennies were made of in the 1950-60s. And also what causes them to get dirty and what is the dirty stuff on the surface of the penny actually called?
Thank you for your time and God Bless.
Lorena S. [last name deleted for privacy by Editor]- Aurora, Illinois
2001
A. Pennies were solid copper back in those days, and until 1982.
You realize that you can burn a piece of paper and turn it to ash pretty easily, whereas you can't burn ash and turn it back into paper. What happens is that the material in the paper is in a higher energy state than the materials in ash. When you light the paper, it releases that excess energy as heat and moves to the lower energy state that we call ash.
The copper in a penny, and most metals, very slowly react with the oxygen in the air, very slowly releasing heat--they sort of very slowly "burn". This copper oxide is the lower energy state, so the reaction is in one direction, towards copper oxide which is brownish in color.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001
October 10, 2013
A. An add-on to this OLD thread: What forms on the surface of clean copper in pure air or oxygen may be copper oxide. But pennies get handled, rained on, pocketed, dropped, etc. Handling in particular deposits salts, fats, dirt, sulfur, and so on.
Many other substances besides oxygen contribute to the surface layer(s), and depending on conditions several different minerals may form part or all of the coating. Sulfides, carbonates, and so on. For a review of atmospheric corrosion of copper, Outdoor Atmospheric Corrosion,
books.google.com/books?isbn=0803128967
has some details.
Paul Tibbals, P.E.
gas & electric
San Ramon, California, USA
(My opinions are not related to nor a statement of my employer's)
Q. My name is Steven and I am doing a science fair project on which juice cleans pennies best. I am using apple, lime, orange and tomato juices. The tomato juice seems to do the best job. I think the reason is the acid in the tomato juice is this the reason or is there another one? Thanks--Steven
Steven S [last name deleted for privacy by Editor]- Fort Wayne, Indiana
2001
A. Hi, Steven. The most important thing is to rely on experiment, not your theory or mine. So I would suggest that you repeat the experiment just to be sure.
I don't think that's why the tomato juice worked best though. Did you squeeze this juice from a tomato yourself, or get it from a can or bottle? If the latter, please read the ingredients and you might see salt listed. Maybe a good experiment would be to test fresh-squeezed tomato juice against bottled?
Good luck with the science fair.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001
A. Hi Steven. I think the reason tomato juice works is because it is sort of acidic. All fruits and fruit juices are acidic. It may also look like tomato juice works but it might also be because tomato juice is red and it gives the penny a red tint and that makes it look shinier.
Minh P [last name deleted for privacy by Editor]- Savannah, Georgia
2003
A. My son did the experiment and he said vinegar ⇦in bulk on eBay or Amazon [affil links] and salt did the best job.
Rose Matthews- Louisville, Georgia
2003
Q. My name is Andrea. I heard that the best juice is orange juice. But I guess tomato juice is better. Will someone try that out and see what cleans better...orange juice or tomato juice? Thanks. Cause I'm doing a science fair project on this ... holla!
Andrea [last name deleted for privacy by Editor]student - Louisville, Kentucky
2004
I think that the 'someone' who is supposed to try it out is you, Andrea :-)
You have ruined your science fair project if you practice "junk science" by trying to make your results match what you think they're supposed to be :-(
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. I think that it works the best because of the acid.
Erika Welton- Canada
2004
2004
Hi Erika. As long as you're sure it's the most acid, you're welcome to guess that the acidity is the reason it works well. That would be a reasonable hypothesis.
But if you're also merely guessing that it's the most acidic, you'll certainly deserve -- and maybe get -- an "F" if the teacher shows you that it's not the most acidic :-)
Please ask him/her for pH paper to demonstrate to yourself that it is indeed the most acidic.
Luck & Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Multiple threads merged: please forgive chronology errors :-)
Hi!
I am doing an experiment for a high school science fair. It is on substances found in the average American household for cleaning pennies. I need ten pages of research for the research paper (double spaced). I have already performed my experiment. I submerged (pre 1982) copper pennies in containers. Each contained 15 mm (1 tablespoon) of rubbing alcohol, baking soda [in bulk on eBay or Amazon [affil links] paste, bleach ⇦ bleach/sodium hypochlorite in bulk on eBay or Amazon [affil links] , dish washing soap, ketchup, laundry detergent w/water, lemon juice, mayonnaise, mustard, vegetable oil, salt water , herbal shampoo, coke, vinegar, or glass cleaner for twenty-four hours. Afterwards, I rinsed each penny in 30 mm (2 tbs) of tap water. Then compiling my research paper, I read that I shouldn't use bleach or window cleaner to clean pennies. Why? I found that they clean rather well. Also, I used Google to find internet references, but I can't find any good ones. Can you suggest some real references? What makes those substances do this? What are the chemical compositions of these substances (for instance:H2O)? Where can I find out? I need references to people who have published works. I need an answer in two days.
Thanks.
PS: What is oxidation and how does it work?
Seth A.- Valencia, California, USA
2002
2002
Many of the people posting here are published, Seth; but I've never heard of a published work about what common household substances clean pennies best and I really don't expect that you'll find one.
But you should probably go to the library for your project. You might also try the Metal Finishing Guidebook. You should find some info in the metal cleaning chapters about cleaning of copper.
What you did not do here yet is submit your results for review. People could probably help you.
But in the end, the best reference is your test results. Many of the mechanisms of cleaning are known only empirically or semi-empiricially, and not fully understood either by professionals or teachers. So if you're right, you're right--end of story.
The reason to not use bleach or ammonia is the safety issue. Bleach is actually chlorine gas dissolved in water; to stay dissolved it requires strong alkali to keep the pH very high, and if you accidentally mix it with a mild acid like vinegar, the chlorine will come out as a gas. People have died from mixing bleach with other materials in a kitchen sink. Suggest to your teacher that s/he hand out a warning about this in big red letters with the assignment next year!
Oxidation is the reaction between oxygen in the air, and the metal surface; the result is rust, tarnish, or other corrosion products.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Hi Seth,
You can find the active ingredients of common household products on the labels. Because these products are usually blends of various components, you won't find a chemical formula on the label, but probably a common chemical name or trade name. In this age of the Internet, you can do searches on trade names to see what chemicals they represent. It is likely that the label will also list a URL for that company, which may lead you to additional useful information.
Good luck!
George Gorecki- Naperville, Illinois
2002
A. I have a good way to clean darkened pennies. I always clean my pennies at Taco Bell, while killing time. The reason is the hot sauce at any Taco Bell cleans those guys up pretty good. Then during a school presentation, you can whip out a Taco, some sauce and make the class wonder what you're up to.
Good Luck!
Brian K.- San Antonio, Texas
2002
Q. My question is: Will lemon juice clean pennies better then cleaning supplies?
Delshaun R.- Sumter, South Carolina
2003
A. Hi, Delshaun. That question has been asked and answered on this site a dozen times; please search the site for the answer and the background info. But the thing is, it would take you less time to try it yourself (and you are probably supposed to!), than to look up the answers someone else got. Good luck!
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003
Q. Hi! my name's Linda. I am working on a science fair project on what juice cleans pennies best. So you guys say tomato juice, huh? let me know!
Linda s [last name deleted for privacy by Editor]- ft Wayne Indiana
January 5, 2010
A. Hi, Linda. No, you let us know what juice cleaned your pennies best. If you try to get the "right" answer, what will happen is you will talk yourself out of writing down what you actually saw for yourself -- and that's not science, that's the poison called "junk science". Whatever works best in your experiment works best and is the right answer.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 5, 2010
by Steve Spangler
on AbeBooks
or eBay
or Amazon
(affil links)
by Janice VanCleave
on AbeBooks
or eBay or
Amazon
(affil links)
Q. Why don't you try grapefruit juice? Tell me how it works out. I'm in seventh grade. What grade are you in?
Anthony C [last name deleted for privacy by Editor]- Hollister, California
January 26, 2010
Q. My daughter is in fourth grade and is doing a science project on "Which juice cleans a penny better?" she is using orange juice, apple, and cranberry juice but she's having a hard time finding simple definitions for their ingredients. Can anyone help?
Marshall Clarke- Miami, Florida
May 8, 2010
A. Hi, Marshall. Fruit juices are complex mixtures of hundreds or thousands of different molecules or compounds. While we may guess that citric acid is an important material in fruit juices, and it gets some of the credit for the tarnish removal, I'm not confident that your daughter is going to make a lot of useful progress taking this tack.
She might measure the pH of the 3 juices and see if she can correlate it to the tarnish removal power of the juice. But in any case, careful recording of observations, and practicing the scientific method is probably what this experiment is really about. The actual answer doesn't really matter, the method does.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 9, 2010
Q. My son is doing a project on What cleans pennies best? His Hypothesis was orange because of the amount of citric acid in has in it. He also gonna try pineapple juice and apple juice
Ayesha asaleem- Philadelphia Pennsylvania
October 2, 2014
A. Hi Ayesha. It sounds like a viable hypothesis that orange juice will clean pennies better than pineapple juice or apple juice except where he says "because of the amount of citric acid in it". Does he know how much citric acid is in orange, pineapple, and apple juice? Does he know as fact that citric acid is a good cleaner? Is it possible that something else in orange juice causes its cleaning power? If the apple juice or pineapple juice cleans better, what will he write?
I think good lab practices like careful gathering and dating of observations, plus not making overly broad claims, are ingredients in a successful project. Good luck
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 2014
Ed. note: Please read our F.A.Q. on the subject. Good luck. And maybe visit your library and ask your librarian for help!
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