Deterioration of appearance is often associated with many of the foregoing problems but this is not the principal cause for concern. Some problems are mainly concerned, however, with aesthetics, and since precast concrete panels are often used to create a beautiful building it is important to avoid situations that will mar this beauty.
Rain water and condensate within the wall are inherently "soft" and thus are able to dissolve lime from cement. Following further reactions involving carbon dioxide, a deposit of insoluble calcium carbonate is left as the water evaporates. The water also tends to become alkaline as it runs over the surface of the concrete, and should it flow over a window there is a danger that the glass will be etched.