I think about 75% of the reason I love margaritas so much is because I'm a salt freak. So it's a huge disappointment to me when the salt on the rim doesn't last. I'll drink around the glass and, when the salt is gone, will usually ask the bartender to rim another glass and pour the rest of my drink into it. 'Cause what's a margarita without the salt?
So I was wondering - when the salt is really nicely stuck on there and it lasts for the whole drink, is that because the glasses are dipped in egg whites, rather than lime juice? If that's the case, would you use just plain egg whites, right from the egg? I've seen powdered egg whites at the supermarket - in the Baking aisle, I think - as well as egg whites in a container next to the egg substitutes in the Dairy section.
Use Kosher Salt, a well-rimmed glass with lime juice then left to sit & dry prior to the pour.
It's because the bartender did it right. The best way I've seen to rim a glass is to wet just the outside edge with a lime or lemon wedge, then dip the glass into kosher salt. Gently tap off any excess salt, and let it sit to dry while you make the rest of the cocktail.