An automatic, low‐pressure packing unit has been designed with control of packing time and pressure to prepare powder samples for diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This unit also provides a polished packing surface that ensures constant measurement height of the sample in the spectrometer. Use of this unit coupled with sample rotation during measurement and control of particle size and size distribution, provides excellent precision in obtaining DRIFTS spectra. For example, repackings by a single person or by several untrained people gave coefficients of variation from 0.8% to 2.3% for each digital spectral value for a coal sample and from 1.3% to 3.7% for thymol blue, a sharp spectral featured organic, rather than the 15%–30% normally found for repackings of the same sample. Thus representative DRIFTS spectra can be obtained quickly and efficiently from a powder sample with a single spectrum using this low‐pressure, mechanical packing device, control of particle parameters, and sample rotation as opposed to previous efforts requiring the repacking of several samples and averaging of the spectra.