Which practice during retouching has the potential to cause hair damage by overlapping lightener?

Which practice during retouching has the potential to cause hair damage by overlapping lightener?

• A. Not Overlapping the Re-Growth Area
• B. Extending Processing Time Beyond Recommended
• C. Overlapping Lightener Onto Previously Lightened Hair
• D. Using a Lower Volume Developer

Answer: (C)

Overlapping lightener onto hair that has already been lightened is risky because the previously lightened sections are weakened and more porous from the first lift. Applying fresh lightener to those strands subjects the cortex to another round of chemical processing, which can push lift too far, break disulfide bonds, and lead to damage, breakage, and a brittle feel. In a retouch, the aim is to refresh the new growth while preserving the mid-lengths and ends, so you apply lightener to the roots and avoid dragging the product onto already-lightened hair. If blending is needed, you should minimize contact with the lighter areas, or use alternatives like a glaze or deposit-only color for blending rather than re-lifting. Lowering the developer strength or shortening processing time can help reduce damage overall, but the specific practice that causes damage by overlapping is applying lightener to previously lightened hair.