Force microscopy has been used to image, both in situ and ex situ, crystals of potassium hydrogen phthalate (KAP) that had been grown from aqueous solution. By introducing water vapor into the growth cell in which the crystals are housed, a localized etching process is seen to occur on the (010) face, which can then be monitored by time-lapse imaging. The etching process results in the development of pits having two distinct morphologies, one that may be linked to local etching at defect sites, and the other reflecting the random nature of the condensation process. The distribution of secondary etch sites is seen to be influenced by the scanning motion of the tip and a model is proposed to explain this observation.