A gypsum dryer/calciner (1) includes a calcining space (2), a first pipe (4) exhibiting an inlet connected to a source of hot gases (3) and an outlet emerging in the calcining space (2); a second pipe (5) exhibiting an inlet connected to a source of gypsum (8) and an outlet emerging in the calcining space, the second pipe being concentric with the first pipe; a force-feeding screw (6) positioned at least partially in the second pipe, the said screw carrying the gypsum along in the calcining space. A process for calcining gypsum and to the plaster capable of being obtained by this process.