What happens when you stir egg white?

Stirring egg white causes the proteins in the egg white to denature. This means that the proteins change shape and become tangled together, forming a solid network. This network of proteins traps water molecules, creating a foam. As you continue to stir the egg white, the foam will become stiffer and more stable. This is because more and more proteins will become denatured and the protein network will become stronger. Eventually, the foam will reach a point where it can no longer hold any more water and it will collapse.