A method for operating an IS machine for producing glass containers includes: introducing a glass gob into a blank mold, producing a parison from the glass gob in the blank mold, transferring the parison into a finishing mold, actuating a vacuum valve for producing a vacuum in the finishing mold from a first actuating point in time and simultaneously measuring the evolution of the vacuum pressure, actuating a finish-blowing valve for generating a finish-blowing pressure from a second actuating point in time that is later than the first actuating point in time by a predetermined duration, such that compressed air is blown into the finishing mold from the top, and simultaneously measuring the evolution of the finish-blowing pressure and checking whether the evolution of the measured vacuum pressure and/or the evolution of the measured finish-blowing pressure has fulfilled a predetermined condition.

A method for operating an IS machine for producing glass containers includes: introducing a glass gob into a blank mold, producing a parison from the glass gob in the blank mold, transferring the parison into a finishing mold, actuating a vacuum valve for producing a vacuum in the finishing mold from a first actuating point in time and simultaneously measuring the evolution of the vacuum pressure, actuating a finish-blowing valve for generating a finish-blowing pressure from a second actuating point in time that is later than the first actuating point in time by a predetermined duration, such that compressed air is blown into the finishing mold from the top, and simultaneously measuring the evolution of the finish-blowing pressure and checking whether the evolution of the measured vacuum pressure and/or the evolution of the measured finish-blowing pressure has fulfilled a predetermined condition.