Polyvinyl acetate (PVA) is a synthetic polymer formed through the addition polymerisation of vinyl acetate monomers, creating long, flexible chains with acetate groups attached. These polar acetate groups give PVA its adhesive properties, allow it to mix well with water and enable strong intermolecular forces between polymer chains. In PVA-based glues, these chains are suspended in water, forming a liquid that can dry into a clear, flexible film as the chains move closer together. When a crosslinking agent such as borax is added, borate ions chemically link the PVA chains together, transforming the liquid glue into a more solid, elastic material with rubber-like behaviour. The degree of crosslinking determines the final texture, with more crosslinks producing firmer, more resilient materials suited for bouncing.