Creating these Rainbow Ice Tunnels has been one of the neatest projects we’ve done in a while. It is the perfect blend of science and art…and it kept the boys occupied for well over an hour!
Be warned, there are a TON of pictures in this post. They were just too pretty not to share them all. :)
Here’s what you’ll need:
Liquid Watercolors (or food coloring)
Salt (we used table salt, but you can also use ice cream salt)
5-6 Medicine Droppers (or pipettes…one for every color)
Plastic Tubs (various sizes) to freeze water in overnight
1. Freeze ice in various plastic containers overnight. When you are ready to begin, pour some of each liquid watercolor into the bottom of your muffin tin and then stir in a teaspoon of salt at a time until it has thickened (but isn’t chunky- I used about 2 teaspoons of salt per color). You can also use a very concentrated mixture of food coloring and water if you don’t have any liquid watercolors, which is what we had to do for yellow/orange because I ran out of yellow liquid watercolor. It didn’t seem to work quite as well as the liquid watercolors, but still pretty well.
2. Grab your medicine droppers (pipettes would probably work better, but we didn’t have any of those). Assign one medicine dropper per color.
3. Have your child apply the salt/watercolor mixture onto the ice and watch what happens!
The tunneling become much more distinct as the ice begins to melt.
We went inside for about 10 minutes and then came back outside for some more fun…and it was amazing to see how much the ice had changed.
The colors on this one got all mixed together as the top layer of the ice block melted, but you can really see the tunneling in this picture!
In this picture, the various colors of ice had formed tiny color pockets within the ice itself.
The Science Behind It: Salt melts ice because it lowers the freezing point of the water, but it doesn’t actually melt the ice unless there is a little bit of liquid water along with the ice (which is normally achieved as soon as the ice hits a temperature well above freezing). As the salt is applied to the block of ice, it creates small tunnels in the ice block itself. The liquid watercolors make these tunnels more visible.