The purpose of this study is to develop a new image processing technique to evaluate decanted structures of undercooled alloys. Dendrite growth theory reveals a trend of decreasing dendrite radii as undercooling levels increases and a similar decreasing trend with increasing convection rates at lower undercoolings. Experiments were performed to evaluate if optical microscopy could be used to quantify decanted surface structures following rapid solidification of eutectic CoSi62 at% alloys. Dendrite diameters decrease with increasing undercooling except for tests conducted with applied stirring at low undercoolings. The higher the convection, the greater the deviation. Marangoni stirring was induced by irradiating a small target area on the surface of levitated molten samples. For a 0.5W laser input, the characteristic diameter was half the unstirred value. For 2.4 W laser input this factor drops to one third. The developed imaging technique was able to produce these trends when identifying the primary phases.