The one and only time a plane I've been on, being de-iced was at HAJ
. We got to the edge of the apron, about to go onto the taxiway to the runway, no holding or waiting for ATC clearance, yet they sprayed us with a viscous, blue gel just before entering the runway. As Cancidas says, it blew off once we got up to speed.
So if we weren't iced up (there was snow and ice on the ground BTW, temps probably at or slightly below freezing), why only use type 4 when we'd been cleared to take off?