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).
Shellac is the most expensive of the gel nail polishes on the market, and the bottles are half the size of the competition. The higher cost for the salon owner is one reason Truong believes other salons might not correct you if you ask for Shellac but choose a different gel polish when picking your color.
I receive a lot of questions about UV and LED lamps for curing gel polish, and thought it might be helpful to provide a brief comparison of the two. Most gel polish manufacturers sell lamps that are compatible with their products, and you will usually get the best results when using a lamp provided by the manufacturer.