A method of operating a plunger in a blank mold (30, 32, 34) to mold a parison from a glass gob, the plunger being driven by a piston in a cylinder to which a source of a pressurized medium may be applied at selected pressures, the method comprising: monitoring the position of the plunger in the blank mold versus time during at least one parison forming cycle beginning at a time t 1 and ending at a time t 4; determining a time t 2 in the at least one monitored parison forming cycle at which a first characteristic of the movement of the plunger during the parison forming cycle is detected, the first characteristic of the movement of the plunger comprising a nonlinearity exhibited by the movement of the plunger with respect to time which is indicative of an upper part of the mold (30,32,34) having been filled with glass from the glass gob; determining a time t 3 in the at least one monitored parison forming cycle at which a second characteristic of the movement of the plunger during the parison forming cycle is detected, the second characteristic of the movement of the plunger comprising a movement-related characteristic of the plunger falling below a preselected level which is indicative of glass from the glass gob having been distributed throughout the entire blank mold (30,32,34) to completely fill it; and during at least one subsequent parison forming cycle, after a gob is loaded into the blank mold, applying a first pressure from time t 1 to time t p2, changing the pressure to a second pressure that is applied from time t p2 to time t p3, and changing the pressure to a third pressure that is applied from time t p3 to time t 4; wherein the time interval between time t 1 and time t p2 is a first predetermined percentage of a first time interval based upon the time interval between time t 1 and time t 2 for the at least one previous monitored parison forming cycle, wherein the first time interval is equal to the time interval between time t 1 and time t 2 for one previous monitored parison forming cycle, or equal to the average time interval between time t 1 and time t 2 for more than one previous monitored parison forming cycle, the first predetermined percentage being less than 100%; and wherein the time interval between time t 1 and time t p3 is a second predetermined percentage of a second time interval based upon the time interval between time t 1 and time t 3 for the at least one previous monitored parison forming cycle, wherein the second time interval is equal to the time interval between time t 1 and time t 3 for one previous monitored parison forming cycle, or equal to the average time interval between time t 1 and time t 3 for more than one previous monitored parison forming cycle, the second predetermined percentage being less than 100%. monitoring the position of the plunger in the blank mold versus time during at least one parison forming cycle beginning at a time t 1 and ending at a time t 4; determining a time t 2 in the at least one monitored parison forming cycle at which a first characteristic of the movement of the plunger during the parison forming cycle is detected, the first characteristic of the movement of the plunger comprising a nonlinearity exhibited by the movement of the plunger with respect to time which is indicative of an upper part of the mold (30,32,34) having been filled with glass from the glass gob; determining a time t 3 in the at least one monitored parison forming cycle at which a second characteristic of the movement of the plunger during the parison forming cycle is detected, the second characteristic of the movement of the plunger comprising a movement-related characteristic of the plunger falling below a preselected level which is indicative of glass from the glass gob having been distributed throughout the entire blank mold (30,32,34) to completely fill it; and during at least one subsequent parison forming cycle, after a gob is loaded into the blank mold, applying a first pressure from time t 1 to time t p2, changing the pressure to a second pressure that is applied from time t p2 to time t p3, and changing the pressure to a third pressure that is applied from time t p3 to time t 4; wherein the time interval between time t 1 and time t p2 is a first predetermined percentage of a first time interval based upon the time interval between time t 1 and time t 2 for the at least one previous monitored parison forming cycle, wherein the first time interval is equal to the time interval between time t 1 and time t 2 for one previous monitored parison forming cycle, or equal to the average time interval between time t 1 and time t 2 for more than one previous monitored parison forming cycle, the first predetermined percentage being less than 100%; and wherein the time interval between time t 1 and time t p3 is a second predetermined percentage of a second time interval based upon the time interval between time t 1 and time t 3 for the at least one previous monitored parison forming cycle, wherein the second time interval is equal to the time interval between time t 1 and time t 3 for one previous monitored parison forming cycle, or equal to the average time interval between time t 1 and time t 3 for more than one previous monitored parison forming cycle, the second predetermined percentage being less than 100%.