Density Experiment with Oil, Water, and Food Coloring!
Reconstructed for the archive — this video never had a written companion, so I wrote one from the original footage with my own custom AI tools and a little good old-fashioned tweaking for accuracy.
Today we did science with oil, salt, water, and food coloring, with both kids helping. They took one look at the setup and pointed out it was basically one of their toys — the kind with colored oil and water sealed in plastic that never quite mixes. They weren’t wrong. Same physics, just out in the open where you can actually poke at it.
We floated oil on plain water, and before it went in I asked whether the oil would sink or float. My daughter, who was three, guessed float and got lucky — she was right. I’m not sure she had any idea what we were testing, but she was thrilled to be part of it. Oil is less dense than water, lighter for the same amount of space, so it beads back up on top no matter how hard you stir. Then we dripped in food coloring, and here’s the part kids don’t expect: the drops just sit on the oil. They’re water-based, so they can’t dissolve until something drags them down through the oil to the water below. For a minute you get a row of little colored beads floating there, doing nothing.
That’s where the salt comes in. Salt is heavier than both the oil and the water, so a few grains punch straight down and grab a pocket of colored water on the way, hauling it under. The color falls in streaks, then blooms out when the salt dissolves and lets go, and the glass turns into a slow lava lamp. Do it a few too many times and every color muddles into brown, which is honestly how ours always ends. That’s still density doing its job; it just stops being pretty. No lab gear needed: a clear glass, cheap oil, food coloring, and a pinch of salt. Just run it somewhere you don’t mind a stain.
I'm Joseph Dattilo — engineer-founder in Lansing, Michigan, author of the FleetHarbor suite, and founder of Date Palm Media. More about me · More writing · Get in touch