A simple procedure for preparing colloidal "black" bismuth films is introduced, which leaves the target cold and does not pollute the recipient. The Bi evaporation occurs in a closed box in the evaporation chamber with an internal radiation shield. The bismuth is evaporated from a tantalum boat at a residual air pressure of 2x102 Pa. The resulting films with a thickness of about 10 mm are structureless down to a spatial resolution of 5.6 mm, they become electrically insulating after 48 h storage time in air, and they show an IR absorbance of above 70% in the 3-5 mm wavelength range. The films are easily removable in an ultrasonic water bath. Thus, these films are ideally appropriate to increase the IR emissivity of microelectronic structures in microthermal infrared failure analysis investigations such as lock-in thermography, as is demonstrated in an application example. The application of this film may improve the thermographic detection limit of heat sources below metallized areas by up to a factor of 10, leading to a saving in acquisition time by a factor of 100. 2005 American Institute of Physics.