Abstract: The invention disclosed relates to air-tight seals between a door and a door frame and is particularly applicable to use with vacuum chambers where both the door and door frame are warped to varying degrees due to the stresses caused by high internal pressures. The invention contemplates a gasket assembly which comprises a retaining means including a groove which extends about and adjacent the perimeter of the door frame and a bead of a resilient solid elastomeric material cured in situ. The bead extends somewhat proud of the groove and while in its plastic state the door may be closed against the door frame and the elastomeric material cured in situ, whereby the elastomeric material conforms exactly to the shape of the door to provide an air-tight seal. A sealing composition comprising about 70-80%/w of a resilient solid elastomeric material and about 30-20%/w of an inert thickening agent is also disclosed.