Making slime from PVA glue and borax

As part of our polymers topic we decided to make slime from PVA glue and borax.  The PVA is a polymer made of long chains.  As you gradually add the borax solution the PVA polymer chains begin to form cross-links.  This makes the solution thicken and become more viscous.  The slime that is made can be squashy and stretchy, and also supposedly bouncy although our pupils didn’t dare put this to the test. 

This is a great activity for science clubs and even primary schools.  Both PVA glue and Borax (Boots and some chemists stock this) are non-toxic, so as long as hands are washed and no chemicals ingested this is safe and fun for all.  We watered down the PVA glue before we started – neat PVA glue is harder to work with and the reaction is too fast for pupils to control the consistency of the slime.  A few drops of food colouring help make the slime look a little more revolting!!

These pictures show some of the better slime samples: