We recently demonstrated the first optical refrigerator based on anti-Stokes fluorescence. Optical refrigeration offers several advantages over more conventional cooling techniques including no vibration, no electromagnetic interference (EMI), low mass, and low volume. Analytical and experimental research is being performed to eliminate heating processes and maximize the cooling power in Ytterbium doped compounds. Current research is focused on developing new techniques and materials for optical cooling. We have developed a bulk cooling technique to measure the cooling capacity of materials without the need for applying dielectric mirror coatings. This method involves bulk cooling measurements with a thermal camera of potential samples for optical cooling. Test configurations include single pass, two pass, or multiple pass tests. Two pass and multiple pass tests use external mirrors to return the pump beam to the fluorescent element to enhance absorption. Comparison of bulk cooling in samples gives a clear indication of which samples will perform optimally for optical refrigeration. The results of measurements and analyses of various samples are presented and compared with photothermal deflection spectroscopy results.