In my mind, striped toothpaste has to be one of the best inventions of the 20th century. But how do they get the stripes in the stuff? And then, how does it not get all mushed together to make a horrid pale purple paste? In fact, the answer is not half as exciting as seeing those lovely stripes every time you brush your teeth. Toothpaste tubes are usually filled from the end and then sealed, but the stripy ones are a bit different. This is because the different colors are kept in separate compartments in the tube so they don't get mushed together and the tubes contain a nozzle system that forces the colored bits out of the tube at the same time as the white stuff. Different nozzle designs allow different toothpaste stripes to be made. Genius.
If you'd like to have a go at making your own stripy icing (probably not too good to brush your teeth with it), you will need a freezer bag, a drinking straw, icing sugar and red food coloring.
