If you are looking for a wonderful selection of Thanksgiving science experiments, look no further! This month is all about STEMs-Giving and finding fun ways to learn with the food on our plate. From homemade butter to pumpkin clocks and now cranberry secret messages, you can explore chemistry and physics with a very Thanksgiving theme!


Have fun this Thanksgiving with a cranberry secret message activity for kids.


Are you a fan of cranberry sauce? I’m not a huge fan, but it’s great for science! We have a few fun ways to explore cranberries this season with cranberry engineering (check out the free printable) and a cranberry sensory bin. Look out for a cool cranberry oobleck coming soon!

Yes, we are playing with food a little bit here! However, it’s a great way to explore acids and bases with the kids for a fun Thanksgiving theme! You may know about acids/ bases from lemons, cabbage PH, and of course the traditional baking soda and vinegar reaction, but what about cranberry juice and sauce?

Below you will see two ways to set up this cranberry secret message STEM activity! Add it to your STEMs-Giving lineup and craft a new kind of “menu” for this holiday season.


Show the kids how they can write and send secret messages to one another!  Paint with cranberry juice and the message is revealed.  It’s magic!  No, it’s science!


  • Small pot
  • Cranberry juice
  • Whole berry cranberry sauce
  • White paper
  • Baking soda
  • Water
  • Paintbrushes


STEP 1. Add 2 cups cranberry juice and 1/2 can jellied cranberry sauce to a pot, bring to a boil over medium/high heat, mixing every few minutes.

Variation:  You can just heat cranberry juice, and leave the cranberry sauce out if you don’t have any.  

Heat ingredients on the stove.
STEP 2. Mix 1/3 cup hot water with 4 tablespoons of baking soda.

Mix baking soda and hot water.
STEP 3. Use the baking soda mixture and a paintbrush to paint a message or picture onto a piece of paper and let it dry.  Alternatively, carefully use a hairdryer to dry your messages.

Paint a message onto a piece of paper.
STEP 4. Carefully pour the cranberry juice into small coffee mugs and let cool. Use the cup of juice as paint and paint the cranberry juice over the dried messages to reveal the secret message.

Variation: Fill a spray bottle with the cranberry juice concoction and spray the paper,

Paint with cranberry juice and reveal the secret message.


How does our invisible ink work? Well, the cranberry juice and jellied cranberry mixture is an acid, and also contains a special substance called Anthocyanin. Acids have a pH rating of 4 or lower and if you have ever set up a red cabbage experiment, you can see how that works. Cranberry juice is around a 2.5 pH rating.

The invisible ink we used to write our secret message with, the baking soda mixture, is a base.  It dried clear after being applied to the paper.

When you paint your paper with the cranberry mixture it will show red from the cranberry juice and a blue/green color where the baking soda secret message was written.  The key to the magic secret message reveal is the change from red to blue when the base comes in contact with the acidic cranberry juice.

So what makes the color change?  It’s to do with the Anthocyanin contained in the cranberries.  Anthocyanins can change their molecular structure, and the color change you see is that structural change happening right before your eyes.  Anthocyanins are found in dark blue and red fruit and vegetables, and are also why our leaves change color in the fall.

Also try our invisible ink with lemons!

secret message reveal


Looking for easy to print activities, and inexpensive problem-based challenges? 

We have you covered…

—>>>  FREE STEM Activities For Thanksgiving


Click on the link or on the image below for more fun Thanksgiving activities for kids.

Simple and fun to do Thanksgiving science activities and experiments along with Thanksgiving theme STEM challenges the kids will love.

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