The effect of different hot pressing and hot isostatic pressing (HIP) temperatures and pressures on the optical properties of spinel was studied. Extinction coefficients of spinel samples were estimated by comparing the measured transmittance with the theoretical transmittance as calculated via a Sellmeier model. Results showed that the relative size of the scattering sites was large compared with the wavelengths of light (0.35-5.5 mu m). Overall, increasing HIP temperature and pressure resulted in decreasing the optical extinction. The lower of two hot pressing temperatures (1620 degrees vs 1650 degrees C) prior to HIPing resulted in lower scatter coefficients after HIPing; this effect was most significant in the infrared.