Passive infrared optical systems sensitive to 8-12μm radiation have been produced for the military for over fifteen years. Gradually, the demand for greater resoution and sensitivity have led to more complex designs. Where previous systems utilized simple germanium optics, present systems use more than one optical material to enable the optical designer to produce color correction over the 8-12μm wavelength range. One class of optical materials extensively utilized for this purpose are infrared transmitting glasses. The glasses used are melt formed, cast or slumped to shape much like any other optical glass. The methods of preparation and fabrication will be presented. Physical parameters important to their optical application will be given and compared to the industry standard, germanium. Methods used in their characterization will be discussed.