The Earth¿s climate is strongly influenced by clouds. The oxidative processing of pollutants in clouds affects droplet size and optical properties, important climatic effects. Common cloud pollutants are naturally occurring organic surfactants forming organic films on the droplet. The climatic effect depends on the rate of atmospheric oxidation of these films and whether any product film forms. In this work we will study the kinetics of hydroxyl radical with stearic acid. Specifically we will (a) demonstrate that a common aqueous cloud oxidant, OH radical, can penetrate deep into the organic film and remove the film, quantifying it penetration distance (b) calculate the effect of the reaction on the hygroscopic properties of a cloud droplet and demonstrate removal of the organic film may cause a cloud to evaporate, (c) Support a STFC/NERC CASE award PhD student¿s studies.