An evaporative three finger thermosyphon (ETT), made entirely of glass, is comprised of three fingers, where one was an evaporator and two were condensers. As evaporating liquid and saturated vapor, water was used inside the ETT, and air was present inside the ETT's condenser fingers, at their tops. This air enables a variation of the effective heat transfer area inside the condensers and, thus, a control of the heat transfer from the evaporator to the two condensers. The cold water used to cool condenser 1 had a cross flow area smaller than that used to cool condenser 2. Experimental investigations revealed that the ETT behavior was controlled by the evaporator heater and by the cooling water in condenser 2. These control features change with elapsed operation time. The ETT behavior was not controlled by the cooling water in condenser 1.