The step that reforms the hair's bonds and stops the chemical action after a perm is called:

Neutralizing (neutralization) is the step after perm processing that rebonds the hair's disulfide bonds in their new shape and stops the chemical action of the waving lotion. Without proper neutralizing, the hair would not hold the new curl and could be left over-processed and damaged. The neutralizer is applied according to the manufacturer's directions for the correct time. Knowing that neutralizing reforms the bonds and ends processing — the counterpart to the bond-breaking step — is fundamental chemical-texture knowledge.