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Cells line up for shiny hair

Q: Why does a child's hair appear "naturally" shiny? And why does vinegar or lemon juice improve the appearance of shine? --Michael M., Cincinnati, Ohio

A: Overlapping cells shingle the outside of a hair like a house roof. See figure. We can feel the shingles (called the cuticle). Pluck a hair from your head. Now, lightly pinch it and move your pinched fingers along the hair- from root to tip. The hair feels silky. Now stroke the other way--from tip to root. Your finger and thumb bump over cuticle cells going in the wrong direction. You can feel them: slightly rough.

Right: [Paula Sicurello/U of California at Berkley] A hair shaft (138 X); flat cells shingle the shaft.

Hair is shiny when those shingles line up and the hair strands lie parallel to each other, says Michael Mead, microscopist at Cincinnati, Ohio. Anything that wears the shingles down (like bleach) or roughens them (like brushing or blow-drying hair) causes the shingle cells to lose alignment and thus the hair to lose sheen.

Enough harsh treatment can wear right through the cuticle and expose the second hair layer-the cortex. Then the cortex, lacking its tough shield, frays like a non-protected rope end. Split ends result and the hair looks rough and drab.

Dipping the hair in an acid solution, like vinegar or lemon juice, shrinks and hardens the cuticle cells. This, in turn, aligns them better and creates a better reflecting surface. That's why vinegar or lemon juice enhances hair luster.

(Answered by April Holladay, science correspondent, February 6, 2002)

Further Surfing:

Exploratorium: Hair

Cognis Research & Technology: Hair cuticle properties