Viscous fluid delivery system and method and valve therefor

A system and method for delivering viscous fluid, having a viscosity in excess of about 100,000 SSU, wherein the system includes a reservoir for a viscous fluid under substantially uniform gas pressure, a dual mode dispense valve having a fluid supply port connected to the reservoir, a fluid dispense port, and a valve head opening and closing the dispense port, the valve head including a high flow valve part and a low flow valve part, a high flow valve part seat defining the dispense port and receiving the high flow valve part for seating the valve head to close the dispense port, the high flow valve part having a low flow dispense opening extending therethrough and a low flow valve part seat defining the opening, the high and low flow valve parts being reciprocally movable together and also relative to each other for dispensing from the dispense port fluid supplied from the reservoir to the supply port, alternately at a high flow rate with the high flow valve part removed from its seat for opening the dispense port, and at a low flow rate with the low flow valve part removed from its seat for opening the low flow dispense opening and with the high flow valve part seated on its seat. A gas knife is formed, for separating and dispensing viscous fluid from the valve head.