How this Works

Elmer's glue is a copolymer named polyvinyl acetate or PVA. It's a plastic made from oil. Borax is a natural mineral mined from the earth that contains boron, sodium, oxygen and water. When you add water to Elmer's glue, the PVA, which is unstable, starts to dissolve in the water. When you add the wet borax, it is slightly acidic, and borax reacts with the PVA to crosslink. This crosslinking causes the mixture to undergo an irreversible gelation reaction. When you boil a raw egg, it is converted into a hard-boiled egg in a similar irreversible process.