The new Age Defense line helps men fight the five signs of aging: loss of firmness, wrinkles, dry, rough and dull skin.

Eberhard explains that you can test to confirm by dampening a clean cloth with a bit of household white vinegar and wiping the glass. She says, "If the part you wiped is clear when dry, hard water ...

Erica Choi, co-founder of Superegg and a licensed esthetician, shares more on glass skin and how to unlock a clear complexion. Glass skin describes a complexion that "plainly looks like glass ...