Being a curious engineer and wondering what an air knife was, I came across the following link: http://www.wisegeek.com/what-is-an-air-knife.htm

But I'm not sure how it would be used to remove the excess emulsion. Does it just push down and even out the emulsion, or would it actually blow a part (layer?) of the emulsion off the substrate? If the latter, how do you keep it from blowing ALL of the emulsion off? Angle? Pressure?