MAKE YOUR OWN S LIME

YOU WILL NEED:

PVA glue Bicarbonate of soda Contact lens solution (it must contain boric acid) Gel food colouring Glitter (optional)

Ghostbusters made green goop a must-have plaything more than 30 years ago. Now, slime is all the rage once more. This time, however, it can be made with items easily available in your local supermarket. Slime is great fun to play with, and its properties are underpinned by some serious science…

WHAT’S GOING ON?

The base ingredient for this slime recipe is PVA (polyvinyl acetate), which is made up of long, spagetti like molecules are surrounded by water that can slide past one another with ease.

The boric acid in the contact lens solution reacts with the bicarbonate of soda to create sodium tetraborate. These sodium tetraborate molecules form bridges between the PVA strands, preventing them from sliding past each other so easily. The more boric acid that is mixed in, the stiffer it becomes, and will gradually become a thick putty. If you get the proportions right you can achieve something that is a marvellous halfway house between a free-flowing liquid and an inflexible solid. If it doesn't work first time, keep experimenting with the qualities of the ingredients until you get marvellous, gooey slime!

2. Add one teaspoon of bicarbonate of soda and thoroughly mix. 5. Keep mixing until it starts to come away from the edges of the bowl, then turn out onto a clean work surface and knead until it reaches the desired consistency.

4. Gradually add one tablespoon of contact lens solution and stir. You may not need all the contact lens solution, so add slowly and stop when the slime starts to thicken.

3. Add a few drops of food colouring, and glitter if you like. Stir well.

1. Tip about 200ml of PVA glue into a large mixing bowl.