slime ball

You will need: Borax, glue, cornstarch, water, and food coloring (optional). You may also want a disposable cup and spoon, but it’s not required.

  1. Mix together a solution of borax and water – add 1 tsp of Borax to 1/2 cup of water
  2. Put 1 Tbs glue and a few drops of food coloring (optional) in the cup
  3. Add 1 Tbs cornstarch to the glue
  4. Add 1/2 tsp to 1 tsp of the borax/water solution to the glue/cornstarch cup
  5. Stir until it starts to stick together. It will probably still feel sticky, but take it out of the cup and roll between the palms of your hands until it holds its shape and is not sticky.
  6. This will stay in the ball shape while you are playing with it, but it will start to flatten out when you put it down.

Here is what’s going on: This is pretty similar to our borax slime experiment. It uses a lot of the same ingredients, but we’ve changed the amounts of each, so we end up with a slime that has a different consistency and is more like a ball. The chemical changes that are going on are the same, though.  In both cases we are forming a cross-linked polymer. The glue is the source of our polymer, which is a large molecule that is made up of lots of repeating subunits. This is kind of like a long chain. The polymer in glue is called polyvinyl acetate (C4H6O2)n. Before we add the borax, the long chains of polyvinyl acetate in the glue can move past each other without sticking or bonding to each other. When we add the Borax, we add a chemical called sodium borate (Na2[B4O5(OH)4]·8H2O). The sodium borate can get stuck or bond with the subunits of the long polymer chains. When it bonds to more than one chain, it starts connecting the polymer pieces to each other, which is called cross-linking. The more you mix the sodium borate and polyvinyl acetate together, the more of these bonds form and eventually the polymer pieces get all tangled up with each other. We’ve added a lot less water than we did with the slime and we’ve added cornstarch, both of these things change the consistency and give us a slime that holds its shape more than with the recipe that we had before.

Have fun! 🙂