Cleaning Pennies With Taco Sauce: A Fun Science Project With Your Kids

Do your kids like to pick up dirty pennies off the street?

Are you looking for a fun and easy science project that engages your kids?

Pennies are great to collect and use for art projects. But you can also use the process of cleaning pennies for a fun science experiment.

In this article I’ll show you how to combine a few dirty pennies with ingredients found in your kitchen to do a science project that will knock your kids’ socks off.

Use ingredients from your kitchen for a fun way to clean your kids' dirty pennies. The taco sauce penny cleaner can also be used as a science fair project.

Why Use Taco Sauce to Clean Pennies?

Because you can. It’s amazing what you can do with ingredients you find in your kitchen, and taco sauce is just one fun option. Taco sauce does a great job of cleaning pennies, and the process is quick and easy.

Whether you need a great idea for your kids’ science project or just want something fun to do with all of those grungy pennies, your family is sure to enjoy this experiment.

Do your kids like to collect coins they find on the street?

boy with penny

There are lots of things you can do with clean pennies. Image source: iStockPhoto.

With this project, you can make coins sparkle, and then save them for a rainy day or use them for a fun art project.

Here are a few fun things you can do with clean pennies:

  • Using a white background, make a penny picture of a face, house or other design
  • Glue pennies on cardboard to make a penny coaster
  • Decorate a plain picture frame by attaching pennies
  • Make tap shoes
shoes with pennies

Use shiny pennies to turn regular shoes into taps. Image source: Pinterest

You Will Need

  • At least 10 dirty pennies (try to collect tarnished pennies that all look the same)
  • Taco sauce
  • Vinegar
  • Salt
  • Water
  • Four small plates
  • Masking tape or sticky notes
  • Pen

Preparation Time

About 15 minutes

Activity Time

About 15-20 minutes, depending on how many tests you run


Kitchen table or a flat surface that is easy to clean up

In this article, we’ll follow the steps as if we are doing a science fair project. However, feel free to use these instructions to clean those pennies so they are ready to use for whatever reason you decide.

#1: Do a Quick Test

Ask your kids the question: “Does Taco Sauce clean pennies?” Have a conversation and come up with reasons why it will or will not work.

Next, it’s time to determine if taco sauce really works as a penny cleaner. Drop a few dirty pennies on a plate and cover them with taco sauce.

Check out my demonstration video.

Smear the taco sauce on the top surfaces using your fingers, but don’t lick them. Dirty pennies are disgusting and taco sauce is hot.

taco sauce on penny

Rub the taco sauce on the penny using your fingers. Just don’t lick them.

Leave the sauce on the pennies for about 2 minutes.

Rinse the pennies in the sink and compare the taco sauce side to the untouched side.

You can now answer the question. Yes, taco sauce definitely cleans pennies.

clean pennies

Taco sauce works to remove the tarnish from pennies.

You can also try carefully dropping the taco sauce on only half of the surface of the penny. Don’t use your finger to rub it around. Keep one side covered with sauce and one side untouched. You want a nice dividing line between the two sides.

Rinse the penny and compare the “washed” and “unwashed” halves.

half clean penny

By cleaning only half of a penny, you can really see the difference.

#2: Design Your Experiment

Now that you’ve determined that taco sauce works on dirty pennies, it’s time to design and plan your science project.

Start by looking at the ingredients in taco sauce: vinegar, tomato paste, salt and water.

taco sauce ingredients

The ingredients found in taco sauce are the variables.

Next, ask a question and make a guess (hypothesis) as to the answer.

In this experiment, we are asking the question, “What taco sauce ingredient is responsible for cleaning pennies?”

The hypothesis can be anything like “I hypothesize the tomato paste will clean the best because it is acidic.” Don’t sweat this—it is your guess and you won’t be graded on it.

Then plan how to test your hypothesis. Develop a materials list and procedure for completing the experiment. What will change and what will stay the same? These will be your variables.

#3: Test Your Hypothesis

Now that you have a plan, it’s time to test your hypothesis. What you are going to do is test the ingredients in taco sauce individually to find out which one works to remove tarnish. Make sure you take notes along the way.

Place the four plates on a table. Use masking tape or sticky notes to mark each plate with a different ingredient (variable) that you are testing: vinegar, tomato paste, salt and water.

Place two equally tarnished pennies on each of four different plates.


Place two pennies on each plate.

Cover each set of pennies with the noted ingredient.


Cover two pennies with each ingredient, as we did here with the vinegar.

Next, smear them around with your fingers. Be sure to wash your hands afterward.

tomato paste

Smear the ingredients over the pennies.

Now, allow the pennies to sit for at least 2 minutes.

Rinse the pennies from each test plate with water. Which ingredient or ingredients cleaned the pennies the best?

You will discover that none of the individual ingredients did a good job of cleaning the dirty pennies.

Did you choose one or multiple ingredients for your hypothesis? Was your hypothesis wrong? If so, don’t panic. Science is all about experimenting.

#4: Test Another Hypothesis

Let’s try another hypothesis. Here’s a hint: maybe two or more of the ingredients work together to react with the copper oxide (the tarnish) on the penny.

Time to revamp the project.

Wash three plates and, again, lay them out on the table.

Use masking tape or sticky notes to make three signs: “tomato paste + vinegar,” “salt + vinegar” and “tomato paste + salt.” Put them on the plates.

Note: Try different combinations of ingredients to find which combo is responsible for cleaning the penny. Keep in mind that you don’t need to stop with our three recommendations. What other combinations can you make and test?

Place two equally tarnished pennies on each of three different plates.

tomato paste with vinegar

Experiment, take 2. Try combining ingredients like tomato paste and vinegar.

Cover the pennies with each of the mixtures, smear them around with your fingers and wash your hands. Then give the ingredients at least 2 minutes to react.

cover pennies with tomato paste and salt

Cover the pennies with each mixture like we did with the tomato paste and salt.

Now, rinse the pennies under water and see which combination(s) worked.

It’s the vinegar and salt combination!

removed the tarnish

Vinegar and salt together removed the tarnish.

#5: Review the Results

The taco sauce penny cleaner experiment is a demonstration of scientific inquiry—ask a question, run tests, ask another question, run tests, ask another question and run tests until a conclusion is reached.

Good science fair projects shouldn’t focus on whether the hypothesis was correct, but instead leave you with more questions than it answered.

So, how did it work? Neither the vinegar or salt alone worked to clean the penny, but mixing them together worked.

shiny penny

Use the dirtiest pennies you can find and shine them up.

The chemistry behind the reaction is somewhat complicated. When the salt and vinegar are mixed together, the salt dissolves in the vinegar solution and breaks down into sodium and chloride ions. The chloride ions then combine with the copper in the penny to remove the tarnish (copper oxide) from the surface of the penny.

It is also well-known that a mixture of lemon juice and salt does a good job of removing tarnish from metals and pennies. (Hint: this may be another great science fair project.)

If you remember, the first hypothesis I suggested was the tomato paste, because it is slightly acidic. It may contribute slightly to removing the copper oxide coating and may do more than the other ingredients individually, but the vinegar and salt are the real power ingredients. That’s ok. We made a guess based on what we knew and then tested it.

girl with piggy bank

Clean pennies are much more fun than dirty ones. Image source: iStockPhoto.

Some final thoughts….

Whether you are putting together a stellar science fair project or cleaning pennies for fun, remember the basic steps: ask a question, develop a materials list, take an educated guess as to the answer (make a hypothesis), write down the steps (process), test your hypothesis, if necessary test another hypothesis (experiment), analyze your results, make conclusions and ask more questions.

What do you think? How could you extend the experiment to try to find more answers? Did this activity cause you to wonder about something else entirely? Could you create a new experiment based on your new questions? Please post a comment or photo below.

Images from iStockPhoto.

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About the Author, Steve Spangler

Steve Spangler is an author, teacher, toy designer, Emmy award-winning television personality and creator of a huge soda mess. His appearances on television demonstrate his passion for making learning fun. Other posts by »

  • Jennifer Ballard

    Thanks, Steve! My son loves to collect coins. This will give him something else to do with them.

  • Eric Dingler

    I really like how you made this educational and fun. A great homeschooling project.

  • kalena

    This would be a great article if it didn’t assume all readers were American. Use of the term *pennies* throughout immediately isolated me. It would have been so easy to substitute this term with *coins*. The Internet does not exist inside a North American bubble! Sheesh.

  • Michael A. Stelzner

    Hi Kalena – Very good point! We are an American company and could have easily said coins, we just were not thinking about that. Not sure if this experiment is only good on the types of metal used in pennies.

  • kalena

    Thanks for the fast response Michael. Might seem I’m over-reacting, but the tsunami of insular marketing campaigns and articles with a strict US angle but global audience is my personal pet peeve. If I see another *Happy Thanksgiving!* email come my way, I think I’ll scream.

  • Steve Spangler

    Hi Kalena – this experiment works with the tarnish that collects on copper coins. It was not our intention to ignore a global audience but instead share an experiment that can be used for a science fair and discovery project using a common copper coin. It will not work on coins that do not contain copper. We will be more aware of our international audience in future experiments. Thanks for pointing this out to us.

  • Steve Spangler

    Thanks Eric. We also like how it makes kids stop and think about how something works the way it does. Is it all of the ingredients or just a few? It’s a simple experiment that includes a lot of discovery and experimentation.

  • Steve Spangler

    Absolutely. And it’s definitely worth trying on other types of coins and with other materials. What will clean the coins in your pocket?

  • Crystal Foth

    Hi Steve! Love the chemistry experiment and lesson for kids! We’ve got some coins to be cleaned for sure. Fun easy project for some down time.

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