Soot particles are a common byproduct of combustion. These sub-100-nm carbon particles can lodge deep in the lungs, leading to cardiovascular and pulmonary health problems. They also contribute significantly to air pollution and potentially to global warming. Recent work has clarified the absorption and scattering properties of bare carbon particles in sunlight, but impurities in fuel often produce carbon particles coated with significant layers of sulfur and other dielectric compounds. To understand the role carbon aerosols play on global climate, and potentially to build remote optical diagnostics of soot emissions, it is necessary to measure the optical properties of these coated nanoparticles. The goal of this clinic is to characterize the light absorption and scattering properties of coated soot aerosols. Soot particles will be generated in the lab by partially combusting ethylene and subsequently coated via a particle coating condenser. Their optical properties will be determined using angle-resolved scattering and cavity ringdown techniques.