Abstract: There is disclosed a jet drop coating system comprising a series of orifices in an orifice plate, and an apparatus for initiating a clean flow of coating liquid through the orifices. There is a fluid supply passage leading to the orifices and this passage is initially filled with air at atmospheric pressure. The system is started up by admitting coating liquid into the passage at a relatively high rate. The pressure of the liquid is in excess of the operating pressure required for clean flowing streams through the orifices. When the liquid enters the fluid supply passage it initially drops to atmospheric pressure. As it continues to flow into the passage, it sweeps the air ahead of it causing some of the air to flow out of the orifices. However, the orifices provide sufficient restriction that the air cannot escape as fast as it is being displaced by the incoming liquid. Consequently the air trapped within the fluid supply passage becomes compressed.