Reaction sintering is presented as a new process to produce AlMg spinel-based ceramics. High oxidation yields of the metallic precursor and full homogenization to single-phase MgAl2O4-ceramics are achieved. Five process stages are distinguished and characterized with particular emphasis on the wetting stage of molten alloy on MgO. If the onset of wetting is efficiently controlled extremely high oxidation rates and full oxidation yields near 100 % are reached at moderate temperatures up to 1000 degrees C. The resulting microstructure is generated without any ongoing shrinkage and it can be characterized by its closed porosity, which suggests the production of gastight porous fittings and components.