I didn't follow the recipe precisely, but it is quite simple. We started with a bag of baking soda in a glass pan. I asked Miss Kiki to use her hands to crush the clumps. She was hesitant at first, because she was not used to getting her hands messy. But once she started, she dug right in. Then I added food colouring into shampoo, I used 2 bottles of hotel shampoo. Then I asked her to mix the shampoo and baking soda with her hands. Then I added a bit of water and she mixed and mixed and mixed.
She wanted to make a snowman...
After she was done with the snowman, I sprinkled citric acid into the dough and she started mixing again... and it puffed. And it continued puffing as she mixed. This was a good time to explain the reaction that happened. She was so amazed with how fluffy it became.
Instead of washing it away, I decided that I wanted to try saving it for another day. So she rolled it into balls, and they are now sitting in my freezer. We'll see how that turns out!