To quantify the energetics of carbon-water interaction as a function of carbon type, mixing with other aerosols, and aging we have assembled a modern cell with a microscope to do contact angle measurements over long periods of time. We have also automated the image analyis using LANL's GENIE algorithm that allows us to get both contact angles and particle volumes in real time, quickly and accurately. Preliminary results on concentrated salt solutions on a freshly cleaved graphite surface show both the initial swelling of the salt drop and the long-term aging of graphite that reduces the contact angle (below).

An image of a salt solution particle on a freshly cleaved graphite surface in our contact angle measurement cell (left) and measured contact angle as a function of time (right).