Garrett Augustus Morgan observed that it is possible to change the basic structure of the hair shaft when certain chemicals penetrate the cortical layer.
Hair relaxing products often require washing and combing with soap which had been made with excess lye. The scalp can suffer severe chemical burns if over exposed to lye or no-lye relaxers.
A lye relaxer consists of sodium hydroxide (also known as NaOH or lye) mixed with water, petroleum jelly, mineral oil and emulsifiers to create a creamy consistency. On application, the caustic "lye cream" permeates the protein structure of the hair and weakens its internal bonds, causing the natural curls to loosen out as the entire fiber swells open. No special deactivation step is required after washing the lye cream out, other than the routine pH adjustment and hair-conditioning.
Manufacturers vary the sodium hydroxide content of the solution from 5% to 10% and the pH between 10 and 14.