fermacell™ Fine Surface Treatment For fermacell® gypsum fibreboards fermacell™ Fine Surface Treatment (FST) is a ready-to-use dispersion material for the universal fine filling of interior wall and ceiling areas. It is also ideal for achieving quality grades Q3 and Q4 if the finish must be to a superior standard. Installation The substrate must be clean, sound and dry. fermacell™ FST must be applied at air and substrate temperatures of not less than +5 °C (max. layer thickness ≤0⋅5 mm per application). We recommend using a fermacell™ spatula to apply the product. The spatula should be dried thoroughly after cleaning to prevent rusting. When sanding use a grit size of 100 – 120. Safety glasses / goggles and a mask must be worn during sanding operations. Remove dust from sanded areas before applying wall coverings or paint. Drying time: dependent on the substrate, layer thickness, temperature and humidity.