That's the sound of children playing.
Now listen to the words and wait.
Time for a 1/2 hour mix and make.
You will need
Household Borax powder (sold in the eco section of big supermarkets)
green food colouring
one jam jar and lid per child
Step 1: Mix Up a Borax Solution
First of all stir up a borax solution.
Take one cup, add some warm water and one tablespoon of borax. Stir.
Let it sit whilst you measure out the rest of the stuff so that any excess settles to the bottom.
Do be careful, Borax whilst in powder form is a little toxic so avoid breathing in the dust. Once it’s in water though, it’s about as toxic as salt… which is more toxic than you might think, ask slugs.
Step 2: Make Sloppy Green Glue - 3 Water: 2 PVA Glue
You will need 3 parts water to 2 parts PVA glue, measure them into your jam-jar and add a couple of drops of dye.
Now screw that lid down and give it a good shake until the water and PVA become one sloppy, runny and slightly foamy green mess.
Step 3: Add 1 Part Borax and Shake It
Now for the cool bit.
Add 1 part Borax solution. A little less for a gloopy goo (for fake boogers); or a little more for more rubbery snot (this can be used as a farty-putty - scoop it out of the jar and press it back to make really rude flatulent reverberations).
Then get kids to shake and shake and shake. Over the next minute or four a lump of snot will form and start bouncing around the jar. I found that a bigger jar helped this happen smoother and faster; though it worked quite well on a small scale too.
Play time now.