A casting furnace for manufacturing a metal casting comprises an interior chamber and a secondary chamber through which the metal casting passes from the interior chamber into external atmosphere. A seal along the secondary chamber surrounds and seals against the metal casting to separate the interior chamber from the external atmosphere in a manner which allows for an extended period of continuous casting. A force producing mechanism typically forces the seal against the metal casting. Multiple seals may be used sequentially to increase the duration of the sealing capability and the continuous casting process.