A powder mixture is described, which is suitable for a layer-wise manufacturing of a three-dimensional object by solidifying a building material in powder form. The powder mixture consists of a mixture of a first polyamide 12 powder and a second polyamide 12 powder, wherein the first polyamide 12 powder is characterized by an increase of its viscosity number determined in accordance with ISO 307 that is less than 10%, when the powder is exposed for 20 hours to a temperature that lies 10° C. below its melting temperature under nitrogen atmosphere, and the second polyamide 12 powder is characterized by an increase of its viscosity number, determined in accordance with ISO 307, by 15% or more, when the powder is exposed for 20 hours to a temperature that lies 10° C. below its melting temperature under nitrogen atmosphere.