Flubber — ~repack~

When you add borax to PVA glue, the borax ions act as connecting bridges. They link the long, slinky-like chains of PVA molecules together. This process is called cross-linking . Suddenly, the liquid glue can't flow past itself easily. It becomes a viscoelastic solid. It stretches because the chains can slide, but it holds together because the cross-links won't let go.