Abstract: An improved accelerator is produced by impact and ball mill grinding gypsum board so that gypsum particles have size of less than one micron in diameter, in the absence of an additive to inhibit calcination.

Abstract: A system for forming a building partition wherein wall panels are secured to opposite sides of vertically extending studs. A metal base member capable of rapid attachment to the edge of a wall panel which base member defines a clip supporting slot. A clip slidably engageable in the slot at divers horizontal positions therealong so that the panels can be attached to studs notwithstanding minor differences in widths of the panels. The clip and the stud cooperate so that the panels can be removed without destruction of the panel, if such becomes necessary during relocation of a partition.