What could be more fun than creating your own green slime to play with? It’s easy to synthesize your own green goo using only Elmer’s glue (the non-washable kind), Borax (found in the laundry detergent section of most stores), green food coloring and water.
In a bowl, have your child mix together about 1/3 cup glue and 1/3 cup water with a spoon or Popsicle stick. These measurements don’t have to be exact. Add a few drops of green food coloring and mix well.
To make the Borax solution, add around a cup of water to a jar. To the water, add about a Tablespoon of Borax. Have your child shake the jar to dissolve as much of the Borax as possible. You are making what is called a saturated solution, so it may not all dissolve! Don’t worry, it will work just fine.
Have your child add about a teaspoon at a time of the Borax solution to the glue/water mix. After each addition, have them stir the mixture together. You should see long strings begin to form and stick together. Keep adding Borax until the mixture doesn’t feel gluey any more. It will form sort of a shiny playdough-like substance. If you add too much Borax solution, it will feel wet. You should be able to just knead it a little to absorb the extra water! The slime is not toxic, but Borax is soap, so don’t let your kids eat it!
I am a biologist and not a chemist, but here is the science, as I understand it.
Mixing Elmer’s glue with water forms a substance called a polymer, which is a long chain of molecules. (A molecule is the smallest amount of a specific chemical substance that can exist alone, like H2O, a single water molecule). The polymer formed by water and glue is called polyvinyl acetate.
The Borax solution (sodium tetraborate) is a cross-linking substance that makes the polymer chains stick together. As more and more chains stick together, they can’t move around and the goo gets thicker and thicker. Eventually, all the chains are bound together and no more Borax solution can be incorporated.
You can store the slime in plastic bags. If you want to make a larger batch, just remember to mix equal amounts of glue and water and add as much Borax solution as needed.
To make your child feel like a “real” scientist, find an old, button up shirt for your child to use as his or her “lab coat”. It’s fun and will protect their clothes. You could even try to find some old safety goggles in your garage for your child to wear, although the ingredients for this project are relatively safe. (Very young children should always be supervised while doing science projects.)