There are obliterated writings that are undecipherable by conventional visible and near infrared monochromatic light photography. Some of them could be deciphered undestructively by middle infrared light photography. Characters were written on paper with 101 kinds of pens. Middle infrared light photographs and near infrared light photographs of them were taken and compared to recognize what kinds of inks is transparent at examined wavelength regions. Based on the results obtained, the combination of ink for drawing and obliterating (which is not deciphered by visible and near infrared light photography, but expected to be deciphered with middle infrared light photography) is selected. From the examined photographs, it is demonstrated that there exist obliterated writings which are undecipherable by conventional near infrared light photography, but decipherable by middle infrared light photography.