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.