Letter# 1293

Cleaning copper pennies in the garage.

USA pennies today are copper plated zinc. Try cleaning a penny by immersing them in a solution of 5% acetic acid (that's vinegar), pinch of cream of tartar (my Webster's Collegiate Dictionary says it is used especially in baking powder and in certain treatments of metals), a pinch of table salt, and a drop of dishwashing liquid (sodium lauryl sulfate, probably).

Cream of tartar is used to help whip egg whites to greater heights; my cookbook, Joy of Cooking¹, warns not to use it in the copper bowls preferred in French cookery for this purpose. The whites will turn green.

The same cookbook says that you can degrease plastic bowls with a mixture of lemon juice and vinegar. These bowls are degreased before whipping egg whites since the grease will inhibit the foaming of the whites.

Electroplaters know how oil sticks to polypropylene. I wonder if it is the terpenes in the lemon that are doing the trick. I'll have to get some lemon skins for my next experiment.

Tom Pullizzi
Finishing.com Inc. - Brick, NJ

Sourcing:

1. Joy of Cooking from Amazon.

I still feel that the best cleaner for home plating is toothbrush and toothpaste. The mechanical action with the very mild abrasive serves to simultaneously remove both tarnish and light soils like fingerprints -- and it's about as "green" as you can get.

For heavier tarnish you can use a stronger abrasive like Bon-Ami [link is to product info at Amazon].

If you start with a new, bright penny, clean it with toothpaste, zinc plate it using Tom's vinegar/sugar/epsom salt formulation, then 'buff' it with the toothpaste again, you will have produced a bright and adherent plate (adherent enough for a science class demo, if not for industrial use) without having used anything poisonous. It would be interesting to know the solubility of zinc in this solution and whether one could safely ingest a small quantity of it.

Ted Mooney
Finishing.com, Inc. - Brick, NJ

Multiscrub, that soft abrasive cleanser, does a nice job, and leaves a water-break free finish. BTW, Ted's comment on the toxicity of home plating solutions reminded me that I had previously written on this subject. The following originally appeared in a finishing.com chatroom. I have adapted the story for the Hotline:

I brought my plating solution to show a 10 year old, and her 7 year old twin sisters. They were interested, as long as their little attention spans will allow.

The 10 yr old was first impressed with the glassware, clips, wires, stirring rods, beakers, etc. They were "cool" - unquote. Where did I get this "cool" stuff? So at least if you can't impress them with your brilliance, dazzle them with lab equipment.

I have been working on a plating solution that is made completely from items available in the home, and without using concentrated acids or bases. It is mighty tempting, I'll tell you, to augment my supplies from finishing houses which I visit. But I have resisted, and I have not resorted to using Muriatic Acid [link is to product info at Amazon] or caustic soda. I was glad for this after my test with the nieces.

But at any rate, it is a MISTAKE to tell a kid that you made all these solutions from stuff in the kitchen. As soon as 10 year old heard this, she tasted the solution. Quick as a kid. Unstoppable. Sounds dumb if you are an adult, a beast of burden, or a baby rabbit, doesn't it? Not to a 10 year old.

I had also decided to use only low voltage batteries for the test. Benchtop Rectifiers would be nice in many ways, but again, I am glad that I am sticking with batteries, and will continue to develop my apparatus using a battery power supply.

As soon as we got started hooking up the cell to the penny, the 10 year old asked if she was going to be electrocuted by the 1.5 Volt, D-cell battery. When I said no, she tried to zap her sisters. I guess she figured: she couldn't kill her sister, but it would be funny to see her fly across the room.

So,

1. make the solutions as nontoxic (and dilute) as possible
2. don't mention the K word
3. use batteries, and you have less to worry about. I can just (shudder) imagine what a little kid will think about when she sees rectifiers plugged into a wall socket. And worse than that, the questions you would have to field.
4. kids seem to be aware that electricity and water don't mix. Hmm...This electroplating demonstration is going to be harder than I thought.
5. Make EVERYTHING spill proof. Don't do anything remotely messy, like cleaning pennies on a sponge pad with: a. toothpaste, b. cleanser, c. vinegar, using: a. toothbrush, b. paper towel, c. rag.
6. While we are talking spill proof: leads, wires, clips, etc. are being phased out of my equipment.
   I am going to bus everything with either soft wires in tracks from here to there, or stiff wires in a bus.
   I think kids should get to touch the equipment, they love that, but it is too easy to knock things over, especially when they start fighting for the next space in the plating cell. Unless you can do this demonstration outside. Then let them go at it, and stop the action by pouring a bucket of soapy water on them. This method also works on fighting dogs, but is much more effective on the animals, I mean the dogs. Just another reason to use low voltage.
7. If you say something you consider pithy, and the 7 year old doesn't share this belief, be prepared for a "duhh". Kids get this from television, which is why it should be banned in favor of the internet. (duhh)
8. You need a plating cell which has its own source of illumination, built in. Kids and flashlights don't mix at all, unless you want to be blinded by the thing every 3 seconds during the entire show.
9. Any thought about shaking the children is caused by your own inadequacy as a chemist and showman, so be prepared with a system that works.

The plating solution must work flawlessly every time, this includes the cleaning cycle. A few chemists from Technic came to the Garden State AESF branch with a gold plating demonstration for Family night a few years back. They did a fantastic job, and the kids went wild. Also, as Ted Mooney has observed, kids immediately grasp Faraday's Law when it comes to time in the tank and gold thickness. They also know shiny, complete coverage, and immediately compare their work to the others. If they see a discrepancy, you will be trying to plate all night. Their young lives will be hopelessly ruined if their sister has a shinier penny.

My test ended rather unceremoniously, as usually happens when you fail to keep giving the kids new reasons to look, and when the table got a little messy. Plating bright copper pennies with a blue, bright zinc plate in this demo was impressive, however flawed. The kids wanted to clean and plate all by themselves, and they enjoyed the process. Now I have to work on making it enjoyable for the adult, keeping the kids enthralled for as long as I want, and teaching some chemistry at the same time.

I think when I get my act together, I will take it on the road. I wonder if a substitute teacher could find happiness showing magic to kids all day?

Tom Pullizzi
Finishing.com Inc. - Brick, NJ

I am doing a science project on what juices clean pennies best. I have found citric acids can clean copper. Could you please give me information on the decaying of pennies.

I NEED IT BY TONIGHT!!

-TRACY

Tracy A.

Did you wait too long to start the project, Tracy? I'd guess that lemon juice cleans pennies best, since it seems to be stronger in acid than other juices are. Is that what you found? As for decaying of pennies, did you know that they actually consist of copper plating on a zinc core? Please see our FAQ: What Cleans Pennies Best -- it has all the info you need. Good luck!

 
 Ted Mooney
Finishing.com Inc. - Brick, NJ

Hi, I am doing a science fair project on which fruit juice cleans pennies best. I am looking for research do you know any sites I could go to or do you know any information on the topic? Could you please e-mail me before tomorrow night because I have to turn it in on Thursday?

Mary N.

I am doing a science project of which kitchen product will clean copper pennies the best. I am trying to gather information for my research. Could you please e-mail me on which sites will give me this information. Thank you for the help.

Michelle B.

I am doing a science fair project on what cleans pennies the best. Do you have any information you could give me to help me out?

Stephanie

Ted Mooney

I am in fourth grade, and am also working on a science project cleaning pennies! We have tried lots of cleaning agents, and found that fresh juices like lemon and grapefruit juice clean pennies fairly well, but vinegar with one teaspoon of salt was by far the best cleaner. Why would cream of tartar make it work even better?

What is the chemical reaction that is occurring? Why didn't red wine vinegar clean nearly as well as distilled white vinegar? I found one internet site that talked about oxidation and hydrogen ions being free to bind, which resulted in cleaner pennies...Can you help me understand the process that is happening?

I really appreciate any help or references you can provide.

Peter W.
- Fairbanks, AK

My name is Keven and I am doing a big science fair project and 5 page report on what acidic household product cleans pennies best. I saw that all of these people have e-mailed you and I was wondering if you could tell me what you told them because I am new to the internet and don't know how to e-mail them. I really don't need the answer quite yet but if you could tell me where I could find different information for my report. THANK YOU, Keven

Keven F.
- Beaverton, Oregon

I think the point of your assignment is for you to TRY some safe chemistry experiments. Stick with fruit juices, toothpaste, soft drinks, and vinegars and you won't have trouble. Do not try any other household products ESPECIALLY NOT bleach, ammonia, window cleaner, oven cleaner, Draino, or liquid plumber -- some of these can burn you right out of the container, or can release poisonous fumes when mixed with other stuff.

We've already said that our GUESS is that lemon juice is the best juice. So, now try it, and a few others like orange, grapefruit, pineapple, tomato, grape, and apple juice, and see what you learn.

Ted Mooney
Finishing.com Inc. - Brick, NJ

If you want to shine a penny coin...and perform MAGIC at the same time...drop a Penny in a glass containing "Coke" (c)...[yep...The Pause That Refreshes kind]. Set it aside...and check it in a week or so. Leave it set long enough and the Penny Disappeared! (Dissolved). Cleans the rust off car bumpers too. Hmm...wonder WHAT it does for a stomach? (Note This is not disparaging to a product of any kind...just natural Chemistry at work)...try it...ED

ED Cherney

You can clean copper pennies by soaking in hot sauce. You do not want to rub the pennies while the hot sauce in on them. Rinse first, after soaking, so you don't rub off surface.

C Moore - OH

See the FAQ on how to plate pennies for a school project. Remember that Nothing Succeeds Like Success, so don't waste too much time studying the subject and spend a lot of time experimenting, and recording your experiments in a notebook using lots of drawings and detailed descriptions.

Nothing will impress your teacher more than a notebook with the results of your experiment. You don't have to discover a new element, but you should be totally honest about the information you found during a search (like in reading these letters), and the results and experiments you made after reviewing the literature. Give references for what you found in your literature search right in your notebook, and separate it from what you discovered for yourself. That is the start of science. That is why you were given your assignment.

The start of failure in your project is when you take information that someone else found, and you try to pass it off as your own work. This approach becomes more enticing the longer you put off your assignment, and the closer the deadline date approaches.

If you ask for information, be sure to thank anyone that helps you. It will make it more likely that people will help the next student that asks for help. You don't have to make a big production out of it; just write a thankyou email in the form at the bottom of this page, and we will post it in the same letter. Never give personal information to anyone on the internet. We expect that email addresses posted here are supervised and monitored by an adult guardian. Always tell your parents or guardians what you are doing on the internet, where you go, who you meet, who sent you email and why.

Happy science project!

Tom Pullizzi
Finishing.com Inc. - Brick, NJ

I HAVE BEEN TRYING FOR MONTHS TO FIND OUT ......

WHAT ACTUALLY IS SCIENTIFICLY HAPPENING WHEN I EMBURSE MY PENNIES IN WHATEVER!!!!!!!!!

I NEEEEEEEEEEEEEEEEDD THIS INFO PRONTO!!!!!!!!!!!!

jenny s. - Taos NM

If you are asking what is happening when a penny dissolves, Jenny, the zinc of which it is made (underneath the copper plating) ionizes into a zinc 'salt'. Ionized materials have totally different properties than their metallic form. Table salt, NaCl, for example, is sodium ions and chlorine atoms and behaves completely differently than sodium metal and chlorine gas.

Ted Mooney
Finishing.com Inc. - Brick, NJ

I'm doing a project on which juices cleans pennies the best. I was wondering, which juice really does? Also, i have to do research tonight on it, and I have no clue what to wright. What's in the juice to make it clean the penny? Well thanks a lot for your help....but i really need this info and FAST!

Sarah E.
- Chesterfield, Virginia

What point am I missing here, Sarah? You just said that you are the one who is doing a project on which juice cleans pennies best. So aren't you supposed to be telling us rather than asking us then?

What juices did you try and what were the results so far? I think that after you tell us the result of your experiment, you'll be able to make some conjectures about "What's in the juice to make it clean the penny". Good luck.

Ted Mooney
Finishing.com Inc. - Brick, NJ

My daughter is doing a science fair project on what juices cleans copper pennies. We know that the answer is lemon juice, but she must also do a research paper. Can you provide some type of information in which we can use is this report. Your help will be greatly appreciated.

Thanking you in advance.

Donna Unruh
- Sauk Village, IL

This question has come up so many times, Ms. Unrah, that we've created a cleaning of pennies FAQ.

Ted Mooney
Finishing.com Inc. - Brick, NJ

I'm doing a science fair project.Its a grad standard . we have all these pieces to turn in at different times. Well I'm doing what cleans pennies the best.

HELP ME GET THROUGH THIS!!

KAMMY S.
- MINNESOTA

After reading this page, and the FAQs it referenced, what questions do you still have, Kammy?

Oh, never, mind, I think I figured it out: "what cleans pennies the best?", right?

Ted Mooney
Finishing.com Inc. - Brick, NJ

I am also doing a science project on what cleans pennies best. My crazy teacher wants 3 references from the internet. anybody know any? PLEASE HELP!! write here and I'll read your message.

THANKS!!!

tiffany h.
- NY

And how many references does s/he want from reliable sources such as books and journals to balance this mass of unreliable, undocumented, untraceable, unstable Internet sources?

Anyway, any search engine you pick will give you dozens. But our FAQs alone should go a long way. Good luck.

Ted Mooney
Finishing.com Inc. - Brick, NJ

Thanks your info helped

tiffany h.
- NY

One last question, you did this test before right? How did you make sure that all the pennies were equally dirty to conduct a fair test!!!!!!!

THANKS

tiffany h.
- NY

Hello, Tiffany. There could be invisible oils on some pennies and not others, or small variations in the copper purity, etc. The oxide that gives the dark 'aged penny' look could be thicker on some than on others. So I don't think there is a good way of PROVING the pennies are equally dirty just from looking at them. Rather, I'd rely on statistics, which in turn depends on randomness.

So what I would do is gather a number of pennies that looked fairly close in age and dirtiness, but I wouldn't kill myself that they be identical. If I was testing 4 cleaning solutions I would get about 20 pennies. Then I would mix the 20 pennies all up. Now with my eyes closed I would divide them into 4 piles. Resist any temptation to re-sort them after you have randomized them this way!

Then I would clean 5 pennies with each solution, rather than just cleaning one. Hopefully when you clean 5 in each solution and look at the stack of 5 you will see a conclusive difference. Good luck.

Ted Mooney
Finishing.com Inc. - Brick, NJ

What in certain liquids cleans pennies the best? I heard it had something to do with oxidation. If you could use "oxidation" in your response that would be great.
thanx

Leon F.
student - Washington, OH, USA

Note to students with science projects: Please see our FAQ on Cleaning Pennies; it will tell you everyhing you need to know!