A method and apparatus for heating and/or pressing sealant of an insulating glass unit. The apparatus may include an oven and a press. The oven includes a detector that detects an optical property of the insulating glass unit. The detected optical property is used to regulate the amount of energy applied to the insulating glass unit to adjust the amount of energy applied to the sealant. The press may include a displacement transducer that detects a pre-pressed thickness of the insulating glass unit. The measured pre-pressed thickness is used to automatically select a press thickness from a set of pressed IGU thicknesses.