Calcined kaolin clay having a high bulk density, improved wet out and slurry incorporation times is produced by using pressure to compact the clay. An air flow system includes at least one blower and an air flow path for enabling air to circulate from the heat exchanger section where it is heated, into the product receiving section for transferring heat to food products, and back to the heat exchanger section for further heating. The L-shaped counter shaft consists of mutually perpendicular first and second shaft portions.