Jamsu isn't a product, it's a technique. And it's one that the experts say has the potential to become as big as contouring or baking. Jamsu stands for "diving" or "submerging" and describes the process of setting makeup by dunking your face in an ice bath. Really. To achieve the look, apply foundation and concealer followed by baby powder, then submerge your face in an ice bath for around 10 to 30 seconds.