A different type of De-icing
Makes sense but it was the first time I had ever seen it. Temperature about 3 degrees C and a bit of drizzle. Flight had arrived from a trans-Atlantic crossing and was departing for a short 40 minute flight.
De-iced on the bottom of the wing only because the ice frozen contamination was more than 3 mm thick. Took longer than normal due to engines having to be shut down at the de-icing bay.