term describing an exterior building surfacing technique. The theory of harling is to produce a long-lasting weatherproof shield for a stone building. The pigment is embedded in the harled material, thus obviating the need for repainting. Harling is a technique used to surface many of the Scottish castles, but it's also used for a variety of common building types. It is long-lasting and practical and well suited to the Scottish weather. Harling is a process of covering stonework, using a plaste… (More on Harl)