A study of the reflection characteristics of over a hundred mirrors of thirty-seven kinds has been made to get data that will permit both a comparison of mirrors and of the various methods and instruments for testing them. Tests were made of specular reflectance at angles from 15 degrees to 82.5 degrees and a new gonioreflectometer was built particularly for this work. The angular distribution data were used to compute average reflectances, and this was done in three different manners that represent three different points of view as to what average reflectance means. A number of alloys of aluminum were made and tested in an endeavor to improve on pure aluminum, and the entire group of mirrors was retested a number of times to determine the degree of permanence of the various metals.
FRANK BENFORD and W. A. RUGGLES, "Some Characteristics of Metal Mirrors and a New Gonioreflectometer," J. Opt. Soc. Am. 32, 174-174 (1942)