Fly Gypsum Putty Gypsum Products Fly Gypsum Putty Fly Gypsum Putty EN 13279-1 C7 · ES 188-1 C7 A one-component, polymer-modified gypsum putty for smoothing internal surfaces before coating. It requires only the addition of water on site and gives a smooth, hard, paintable surface – ideal over cement mortar, gypsum plaster and gypsum board. Data Sheet