Styro Brush On Coating ST is a highly polymer modified and fiber reinforced Portland Cement based coating designed to protect polystyrene foam insulation. The product is pre-blended and needs only to be mixed with water before application. The rigid insulation boards and reinforcing mesh are first mechanically fastened to the substrate with mechanical fasteners and / or adhesive. Mesh all corners and joints. Pre-treat the meshed corners and joint areas with the ST Coating. When the pre-treated areas begin to dry (turn a lighter color) use a brush or steel trowel and apply BrushOn Coating Kit ST mix in a 1/16 to 1/8 inch thick butter coat over the face of the insulation board.