A preform intended for the manufacture of a metal foam having a porosity of between 62% and 85%, the preform including a set of precursors in the form of balls formed of a mixture of 12% to 25% of organic binder, 72% to 87% of sodium chloride and 1 to 3% of kalinite. The precursors have a diameter of around 1 mm to 10 mm, and preferably 4 mm, the precursors being obtained by granulating the mixture using a fluidized bed process.