A description is given of an apparatus for measuring the total normal thermal emissivity of sheet materials up to ⅜ inches in thickness at temperatures from 140 to 500°F without contact or damage to the surfaces viewed. An analysis of possible errors is made which shows the outer limits of absolute values to be within ±1 percent of black‐body emission. A table of emissivities as measured are given with values from the literature included for comparison. By minimizing errors due to reflection, the values for poor emitters are found to be somewhat lower than usually reported and are held to be more accurate.