Tie-dye Milk

I’m reposting this experiment in honor of my daughter’s classmate, Timmy, who passed away two weeks ago.  He was an amazing little boy who loved tie-dye and rainbows and inspired everyone who met him.  Even if your kids are driving you crazy today, hug them, look them in the eye and see them for the wonderful gifts that they are.

Food coloring isn’t just for frosting any more!  You and your child will be amazed as you watch the forces of surface tension at work in this “brilliant” experiment. 

All you’ll need is a small, shallow dish or plate, milk (2% or whole milk work best, but skim milk works too,) dishwashing liquid, Q-tips and food coloring. 

I would recommend putting down newspaper and having your child wear an old shirt, since food coloring stains. You can even help them make a lab coat from an old button-down shirt, by writing their on the pocket with permanent marker.  

First, add enough milk to cover the bottom of the dish.   In a separate small container, mix together about a half cup of water with a squirt of dish-soap (a teaspoon or so.)  Have your child put several drops of different colored  food coloring into the milk (maybe two drops of each color.)

Finally, let them dip a Q-tip into the dish-soap mixture and then touch the Q-tip to the milk.  The detergent will break the surface tension of the milk and the food coloring will swirl around in interesting patterns, as if by magic. 

Let them play with it!  It works better if they don’t stir, but they can keep re-wetting their Q-tip with soapy water and touching it to the milk.  If you want to, have them compare how the experiment works with skim milk versus whole milk.  Your sixth-grader will love it as much as your two-year old does!

Have your child draw a picture in thier science notebook of how the milk looks before and after they touch it with the Q-tip!  Help them take a picture of it and tape it their notebook!  Can they write the words “surface tension”?  Help them describe what they see with words or pictures!

What Happened?  Imagine that surface of liquids is a stretched elastic skin, like the surface of a balloon full of air. The scientific name for the way the “skin” of a liquid holds together is surface tension.  When the skin of the liquid is broken, whatever is underneath will be able to escape, like the air rushing out of a balloon. 

In this experiment, the surface of milk is like the elastic skin and dish detergent is what breaks the “skin” of the milk, sort of like a pin popping a balloon.  Food coloring and more milk then escape from underneath the milk’s surface, swirling to the top.

Have fun!  Click here to see my video on how to make tie-dye milk.

Tags: experiment, food coloring, kids, milk, Science, surface tension, tie-dye