Pin Wash
Pin wash (abbr. of «pin-point wash»), modelling jargon referring to a selective brownish-black wash applied to panel lines, around rivets, bolt heads and other tiny surface details of scale model vehicles, buildings, weapons, and figurines. The model needs to be sealed with clear gloss varnish before a pin wash is applied, to prevent the wash from seeping into and staining the base colour of the model. See Weathering Small Scale AFVs