Science Projects on Which Soap Cleans Best

Comparing soaps for science
••• soap container image by timur1970 from

When attempting to come up with a science projects, sometimes the best idea is a simple and inexpensive one. Basing your project on the cleaning properties of soap, for instance, can lead to multiple projects that are science fair worthy. These projects are not complicated and the total price of the project is typically quite low. Keep in mind, that when making soap from scratch, as in the Homemade Soap project, some chemicals such as lye can be dangerous and should be handled with care.


Test different soaps to see which is the most effective in killing germs. For the experiment, you will need two agar dishes, several different brands of soap, a transparent graph and test subjects. For each brand, have your testers first touch one dish and then uniformly wash their hands with the soap, then have them touch the second dish. Measure the difference in bacteria between the first dish and the second dish using the transparent graph. Try this with all of your soap brands and determine which brand has the biggest difference between the first and second agar dish, that is, which kills germs and cleans better.


Determine which laundry detergent soap is the most effective in cleaning stains. For this project you will need 60 squares of white cotton, a bowl, a spatula, a colorimeter and materials to make stains (such as:

  • cranberry juice
  • black coffee
  • mustard)

Create the stained cotton by mixing the stain materials in the bowl, dunking in the cotton squares, and hanging them up to dry. Throw 10 of the squares in the laundry on the cold cycle with one of the detergents. After washing and putting them in the drier, use a colorimeter to determine how white the cotton is. The detergent that produces the whitest cotton squares has the best stain-cleaning ability.

Homemade vs. Store-Bought

Test homemade soaps versus brand name soaps. The steps of the project itself are similar to the “Germ-Killers” project. You will test to see which of the soaps kills bacteria the most effectively. The time-consuming part of the project will be creating your own soap from scratch using such materials as lye, water, shea butter, coconut oil, jojoba oil. It is best to consult a professional soapmaker for this project to ensure that you handle all materials properly. Test several different types of homemade soap versus several name brands of store-bought soap.

Green vs. Synthetic

In an effort to be friendlier to the environment, many "green" (natural) soap brands have come out in the last decade. Do these soaps clean as well as dependable name brands that have been around a long time? Test the green brands against regular brands to answer that question. You can test the soaps for cleaning ability, germ-killing ability, bubble-forming and moisturizing ability, as well as pleasantness of scent and any other factors you can think of.

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