Lincoln and I tried out this art/science experiment a couple of weeks ago after seeing it on The Artful Parent. It goes really quick, so we did it a few times. It would be a great way to use up milk that is about to go bad!
To start, pour a shallow amount of milk into a pan--we used a 9x9, but really, it makes no difference at all what kind of container you use...bowl, pan, pie plate, avocado green tupperware bowl from the '70s...you get the idea.
Drop food coloring into the milk. We found it worked best to hold the food coloring high above the milk so it made a bigger dot. Do as many dots as you like.
Drop a single drop of dish detergent into the center of the pan (really, you don't need much...) and watch the colors move! It goes fast. I gave Lincoln a toothpick to move the colors around after they slowed down. Another way to do the experiment is to dip a cotton swab in the soap and place that into the milk instead of just dropping the soap in--we'll give that a shot next time.
We also decided to make some prints since the colors made such a cool design. I took some pieces of paper and just laid them lightly on top of the milk and paint, picked them up, and let them dry.
If you are interested in the science behind why this works, I found this description here:
"As soon as dishwashing soap is added, the drops of food coloring and the milk rapidly mix together. The soap is made of molecules that have two ends: a fat-friendly end and a water-friendly end. One end of soap attracts the fat in milk (the non-polar end), and the other end attracts the water in food coloring (the polar end). The food coloring mixes with the milk because the dishwashing liquid acts as a bridge between the two."
Try it! It's easy, quick, and pretty entertaining.