The distance of migration is inversely correlated with the molecular weight of the protein (small proteins move faster through the gel than large proteins do and therefore migrate further down the gel).
Gel nail polish is, hands down, the most popular service at nail salons right now. But many women may not be getting what they think they're getting. CND's Shellac is a brand of gel nail polish. It was the first to hit nail salons, offering a no-chip, super-shiny nail color lasting up to two weeks.
Although gel manicures are generally only done in salons, OPI and CND are both pushing at-home versions. The polishes are expensive (think $20 a bottle) and the U.V. lights used in salons can cost $600. (The at-home versions start at around $40.) A gel manicure can last up to 20 days. Here's Dallas's take; she says gel manicures are best done in a salon: CND is the best brand for the gel manicures.