Colorado Cosmetology Written Practice Exam

The correct answer is thio relaxers. Thio relaxers, which contain ammonium thioglycolate, are specifically formulated to alter the structure of resistant hair. They work by breaking down the disulfide bonds in the hair, allowing for better penetration and more effective straightening. This makes thio relaxers suitable for clients with coarse or resistant hair types, as they provide a gentler, more effective solution than some other chemical straighteners.

On the other hand, fillers are typically used to even out porosity or add moisture, but they do not contribute to the straightening process. Lye relaxers contain sodium hydroxide, which can be very strong and may not be the best option for resistant hair, as they can lead to over-processing if not handled carefully. No-base relaxers are generally milder but may not have the same efficacy on very resistant hair compared to thio relaxers. Thus, thio relaxers are the preferred choice for effectively processing resistant hair during a chemical straightening treatment.