Alumina preforms containing artificial pores were sintered at 1630 degrees C in air and vacuum. Glass penetration into the alumina preforms was conducted at 1600 degrees C in air. It was found that the trapped gases in alumina preforms sintered in air caused the random and incomplete filling of the smaller and larger artificial pores. In contrast, the pores in the alumina preform sintered in vacuum were completely filled during glass penetration.