Color Swirl Milk Experiment

David loves “projects” so I’m always looking for fun, simple activities we can do together. I recently came across this idea for a preschool science experiment involving milk and food coloring. Sold!

To do this “color swirl” experiment you only need a few household materials: a pan or wide-rimmed plate (I used an 8×8 baking dish and it was perfect), dish soap, milk (high-fat or whole milk work best), liquid food coloring, Q-tips and/or toothpicks, and *optional* paper (watercolor paper or construction paper, not computer printer paper)

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Once you’ve gathered your materials, the fun begins! Start by pouring milk into the pan until it just covers the bottom of the dish. Drop 4 or 5 drops of each color of food coloring near the center of the pan so the colors are close together. Tell your preschooler to resist the beautiful colors and keep his hands to himself for 2 more seconds.

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Dip the end of a Q-tip into the center of the colors and watch what happens (nothing, except maybe you push a bit of milk around). Now ask your child what you think will happen if you dip the same Q-tip into soap before dipping it into the center of the milk (“What is your prediction, child? Will anything be different? What do you think will happen?”). Now, generously coat the end of the Q-tip or toothpick with dish soap. Dip the Q-tip into the center of the colors and hold the Q-tip still (I know, holding still is a difficult concept for a preschooler, but trust me–it’s worth it!). Now watch the colors explode as they dance away from the Q-tip!

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Now dip the other end of your Q-tip in the dish soap and poke it down somewhere else in the dish. It’s like magical little fireworks repelling away from the Q-tip!

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I was curious about the science behind the color swirls so I did a quick internet search and found this great website with a thorough explanation. Turns out that dish soap is bipolar–not in the manic-depressive sense, but in the hydrophilic polar (water-loving) and hydrophobic non-polar (water-fearing) sense. When the water-fearing part of the dish soap connects with the fat in the milk, the magic happens. As all of the little soap molecules start racing around trying to find the milk-fat molecules to connect with they push the food coloring out of the way, creating those wonderful swirls.

We thought that the colors were so pretty that we decided to try capturing them on paper. I just cut a few pieces of artist paper down to a size that would easily fit in our pan and we laid each piece straight on top of the color swirls before gently lifting it back up. The color swirl paper looks really beautiful (and, just in case you’re wondering, a few days later they still smell fine!).

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After playing with four batches of milk in the pan, it was time for another experiment. I came up with this one all on my own. What will happen if we replace the milk with water, take away the food coloring, add a bit of dish soap and switch out the Q-tips for scrub brushes? David couldn’t wait to find out!

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Ta-da! Prest-o, clean-o! Now that’s one science experiment that can keep all of us happy.

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