The optical properties of coated soot aerosols produce the greatest uncertainty in climate change models. This project aims to measure the scattering and absorption of light by sub-micron sized soot particles similar to those produced in diesel exhaust. Total absorption and scattering cross sections of 635-nm laser light are measured using cavityring down and angle-resolved scattering techniques. Soot particles are created in situ by partially combusting ethylene and coated with a volatile organic compound.