The results of transmission and reflectivity measurements in the infrared and theraherz region for paper made at the end of XX century and the beginning of XXI are compared. Modern Fourier transform spectrometers allow for reliable transmission measurements below 0,01 typical for paper transmission. The changes in paper spectra due to the changes in production technology are clearly visible. These changes become worldwide in the middle of 90ties. This gives us the opportunity to establish the time limit of production time for investigated paper. Sometimes such information is valuable for evidentiary purposes. The absorption bands observed in terahertz transmission of “modern” paper may obscure the bands characteristic for dangerous chemicals like explosives making more difficult terahertz spectroscopic screening of paper packed items.
spectroscopic screening of paper packed items.