1 Wearing the goggles and maybe gloves, put the hydrogen peroxide in the soft drink bottle. (Your favourite grown-up might want to help.)
2 Add a few drops of food colouring – your choice!
3 Now drop in about 15ml of dishwashing liquid (that’s roughly a tablespoon) and swirl it around.
4 Grab the small cup and tip the yeast sachet in it, then pour in 45ml of warm water (not too hot – you’ll kill the yeast and burn your fingers!). Stir it for 30 seconds.
5 OK, here goes: pour the contents of the cup into the soft drink bottle. Stand back and watch foamy gooey mega-toothpaste shoot out of the top!
This is a really fun experiment guaranteed to make a huge mess in the kitchen – so it’s best to do it on a table outdoors! What you’re going to make isn’t really toothpaste, but it looks like it, although on a huge scale. Basically, what’s going to happen is that you are going to mix a common hair product with some dishwashing liquid, a bit of food colouring and some microscopic fungus and make a gooey geyser whoosh out of a soft drink bottle. Fun, right?