Harling is a Scottish term escribing 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 is also used for a variety of common building types. It is long lasting and practical and well-suited to the Scottish weather.