Food coloring is not only used in food and beverage preparation, it also is used in science as well. Food coloring is very useful in demonstrating how a substance moves through water and other liquids and diffuses throughout it. While watching food coloring move through water is simple, separating food coloring from water requires more effort. Blue food coloring is often used in these types of demonstrations because it is easy to see and you can separate it from water within minutes.
Place several drops of blue food coloring into a pan of water and allow it to diffuse into the water completely.
Heat the water on an oven burner or place it in sunlight for several days to evaporate the water out of the pan.
Allow the water to evaporate away and you will be left with the food coloring remaining in the pan.
Adding several drops of bleach into water laced with blue food coloring will cause the food coloring to disappear and change the water back to clear, however, the solution will now be toxic.
You can also add vinegar to the boiling water and stick a piece of white yarn in it. It will collect the blue dye and turn blue, leaving the water and vinegar either clear or a milky color as a result.