First, let us start by saying this experiment is meant to be a fun way for kids to learn about acids and bases. Precision Laboratories products are not approved for use as medical devices. Products and product information is for informational purposes only and not intended for use to diagnose, treat, cure or prevent any medical condition.

With that said, let’s get to the fun stuff! Today, we’re going to test the pH of your saliva and determine how some foods might raise or lower the pH.

By now, you know from our many posts about pH that acids have a pH below 7 and bases have a pH above 7. A pH of 7 is neutral. The lower the pH, the higher the acidity, and the higher the pH, the higher the alkalinity. For a more in depth perspective, review some of our other blog articles about pH, like “Back to Basics: Acids, Bases & the pH Scale.”

As with any experiment, let’s start by creating a hypothesis. What do you think the pH of your saliva is? How do you think acidic foods will affect the pH? How do you think alkaline foods will affect the pH?

Next, do some research to find examples of acidic foods and alkaline foods for your experiment, and gather your supplies.

Materials

  • Plastic cups or spoons
  • pH 1-14 test strips
  • Alkaline foods, for example, almonds, radishes, grapes, pineapples, greens, avocados, etc.
  • Acidic foods, for example, oranges, soda, pickles, chocolate, cooked beans, sweetened fruit juice, etc.
  • Laboratory Notebook

Procedure

  1. For some of you, this part may be fun, and for others, it will probably be a little gross. It’s time to spit. The best time to test your saliva is in the morning before you eat, drink or brush your teeth. Collect saliva in your mouth and spit it into a cup or spoon.
  2. Using a pH 1-14 test strip, dip the strip into the saliva. Remove immediately and compare to the color chart. What is the pH of your saliva? Is it close to your initial guess? Record the results in your laboratory notebook.
  3. You can draw this experiment out for as long as you want to, or you can make it shorter if you’d like. Start by eating lots of alkaline foods in your diet. You can try this for a day, a couple of days, even a week. Again, it’s up to you.
  4. Test the pH of your saliva 3 times per day by following step number 2. Don’t brush your teeth before you test your saliva. Record your results.
  5. Once you’ve had enough of eating mostly alkaline foods, switch to eating mostly acidic foods. Again, test the pH of your saliva approximately 3 times per day by following step number 2. Record your results in your laboratory notebook.
  6. Lastly, switch back to eating as you normally do. Test your pH 3 times per day, and record your results in your laboratory notebook.

Compare your results across the three different diets (alkaline, acidic and regular). Did your diet affect the pH of your saliva? How do your results compare to your hypothesis? Why do you think it’s best to test your saliva first thing in the morning? How do you think brushing your teeth affects the pH of your saliva?

Going Further

To answer that last question of how brushing your teeth might affect the pH of your saliva, try testing the pH of your saliva a few times after brushing. You could even mix this into your experiment if you are testing the pH of your saliva for a few days with each diet.

While spitting isn’t something we normally encourage, for the purposes of this experiment, thanks for joining us to test your spit!