Science on the Light Box: Oil and Water Revisited (with a little color theory)

I wanted to revisit our light box experiment with oil and colored water. Last time I noticed how well the different colors of water blended together in the experiment and how beautiful the colors were when backlit by the light box.

We always blend our secondary colors. I only have red, yellow, and blue tempera paints because that saves a little money and storage space. So the children are very familiar with making orange, green, and purple by mixing red, blue, and green. I had never done a formal introduction to the color wheel and the terms primary and secondary colors though. So, first we did a brief (5-10 minute) activity using paints and cardstock to introduce the color wheel. We put the three primary colors on the paper. Then we mixed the secondary colors in between each pair of primary colors.

Next I took small squeeze bottles filled with clear water and set them next to each color on the color wheel. First we colored the water with the three primary colors and then we mixed those to make each secondary color. We ended up with six squeeze bottles filled with different colors of water (red, blue, yellow, purple, green, orange).

I got out both light boxes and trays so that each child could play on their own. We took a moment to appreciate how pretty our bottles with colored water looked in an empty tray backlit by the light box.

I poured a small amount of cooking oil into each tray. I just put enough to cover the bottom of the tray with a shallow film of oil. Then the children began to squirt colored water onto the oil. The drops of water stay separate in the oil and float around like individual colored puddles.

If you are careful you can even make some simple shapes. I was able to make caterpillars and flowers for the children.

After a few seconds the surface tension of the oil releases and adjacent droplets of water combine. We were using the word "absorb". The children learned they could direct a stream of water from a squeeze bottle to manually break the surface tension and force a big drop to absorb smaller droplets. They made up a game of superheros and villains where the large superhero drops would absorb the small villains trying to attack them.

Everyone had a great time and we didn't quit until all the water had been used up from the squeeze bottles about an hour and a half after we began.

If I repeat the activity again, I will give each child a set of the three primary colors and encourage them to do their own color mixing as they play. I'll ask them to make a purple drop, green drop, and orange drop from the appropriate component primary colors. I'll see if their fine motor skills are good enough to make their own adjacent drops of primary colors without breaking the surface tension. Then we can all wait until the surface tension dissipates and the two colors swirl together to make the secondary color. It is all beautiful on the light boxes.