Figure 13 illustrates the urea bisulphite solubility result of the perming damaged hair samples. The findings indicate that the solubility of hair samples is inversely proportional to hair damage when the pH of perming treatments is more alkaline. The solubility of control sample is 2.89%, which is slightly higher than 2.78% of the perming treatment conducted at pH 7. However, when the perming treatments are carried out at pH 9 and pH 10, the solubility further declines to 2.34% and 2.29% respectively.