New York State Cosmetology Practice Exam

When an alkaline substance is applied to the hair, it causes the cuticle, which is the outer layer of the hair shaft, to expand or swell. This is because alkaline substances have a higher pH level, which disrupts the natural pH of the hair and causes the cuticle to open up. This can make the hair appear dull and frizzy. Option A, bleaches the hair, is incorrect because alkaline substances do not have any bleaching properties. Option B, strengthens the cuticle, is incorrect because although alkaline substances can temporarily make the hair feel stronger, they can actually cause long-term damage to the hair. Option D, closes the cuticle, is incorrect because as mentioned before, alkaline substances actually cause the cuticle to open up. Therefore, the correct answer is C, as it correctly explains the effect of an alkaline substance on the hair's cuticle.