I never turn out professional looking cakes, but I aim for fun. My son, turning 6, wanted a mad science birthday party. I saw a few ideas online, but thought a lot were over his head (and perhaps my abilities). So, I went with a simple cake plan, and added some pizzas with an experiment ON the cake…
I baked 3 cake mixes (marble, Duncan Hines), 2 thin 10×16 slabs, layered, and the other in a Wilton small sports ball cake pan I rented. I iced them with French vanilla bought icing. Then I added green food coloring to the remaining icing and finished the “ball”, so the bottom half was green (supposed to look like green liquid in the bottom of the flask).
I used cookie “scribblers” to draw a few other sciency things, and my son’s name, and age on the slab. I also detailed a few green “bubbles” “floating” up in the white area of the flask. I cut a small indentation in the top of the ball/flask.
Inside I set a “baby soda bottle” test tube (bought on line from amazon, also sold by Steve Spangler Science). These are virtually indestructible and have a tight screw on lid.
I had read (in preparing for the experiments for our party) about home made lava lamps on a website called KidScience. So I prepared this in the test tube. fill it 1/4 with water, then top it up to about 3 cm from the top with vegetable oil. Put in a few drops of green food coloring Just as people begin singing, I dropped in 1/2-1 tablet alka seltzer, and screwed the cap on tight. I also had used icing to stick a bunch of white cotton candy to the lid to simulate steam.
So at the time of serving, the flask was bubbling vigorously (which was good because I forgot the candles and no one noticed!)
It was good fun, and easy!