An agitation mechanism for a gypsum processing apparatus which includes a housing having a bottom wall and at least one side wall. The housing can be constructed and arranged to receive and process gypsum-based products. An agitator frame having a similarly shaped cross-section to the cross-section of the housing is provided and positioned adjacent the bottom wall of the housing. The agitator frame is pivotally connected internally to the housing for reciprocating movement between first and second positions. The agitation mechanism is operable for preventing fluid channeling to ensure good fluidization of the gypsum products from collecting adjacent the bottom wall of the housing.