I believe specific gravity. Things like "how do you properly make a B-52?" ( http://www.cocktailhunter.com/bartender-guide/specific-gravity-chart/ http://www.

I believe specific gravity. Things like "how do you properly make a B-52?" ( http://www.cocktailhunter.com/bartender-guide/specific-gravity-chart/ http://www.cocktailhunter.com/bartender-guide/specific-gravi... ) or a Pousse Café ( https://youtu.be/4OJd_phsa5w https://youtu.be/4OJd_phsa5w )