I was so excited to see this color mixing discovery bottle since color mixing is an activity that we spend a lot of time on.
To make this discovery bottle, I filled the bottom one third of the bottle with water colored with blue food coloring. Then I heated cooking oil and mixed in yellow powdered tempera paint. I stirred and stirred to try to get the paint to dissolve. It eventually dissolved enough, and I spooned it into the bottle. (I did this slowly because I was try to avoid putting any undissolved powder into the bottle). I'm not completely happy with the bottle because the yellow oil clings to the sides and makes the blue a little cloudy, but I've worked on it for several days, and I think this is as good as it's going to get.
The liquid turns a nice shade of green after shaking it vigorously. Then it immediately starts to separate into yellow and blue again.
I have to admit that I am much more impressed with this than the girls are, but they have had fun with it, too. I'm looking forward to making more coloring mixing discovery bottles for E(2)'s science shelf! (I'm hoping to find blue lamp oil because I think this would work much better with blue lamp oil and yellow water).