An adhesive applicator has a nozzle through which adhesive can be dispensed to sheets of a set as the sheets are driven seriatim past the nozzle. Adhesive is furnished in a cartridge which is pressurized so that the adhesive is delivered from the cartridge to the nozzle under pressure. A valve controls the flow of adhesive from the nozzle, and the valve is under control of a logic and control unit. The logic and control unit receives signals from various sensors or detectors indicating, inter alia, the presence of an adhesive cartridge, the level of adhesive in the cartridge, the flow of adhesive from the nozzle, and the amount of adhesive in a collection bottle which receives surplus adhesive dispensed from the nozzle but not applied onto a sheet. The logic and control unit is capable of operating the valve that controls flow of adhesive from the nozzle so that adhesive is selectively dispensed from the nozzle to all but one sheet of a set of sheets. A purge cycle is initiated if adhesive does not flow from the nozzle when commanded to flow by the logic and control unit.