Muslin is a tightly woven, cotton, theatrical fabric used for the covering of any surface that might be painted or reflect light. Widely used for scenery flats, small backdrops and cycloramas. Traditionally, a seamed muslin backdrop has seams that run horizontally so that when it is used as a backdrop, the seam blends into the horizon. Muslin is also commonly used as a canvas because it takes paint very well. Scenery flats are often covered with muslin, then sized (made to shrink with the use of water and glue or paint) so that it is stretched tight. If you do not tack down muslin before you paint it, it will shrink unevenly and could cause distortion in your image. Muslin can be either FR (Flame Retardant) or NFR (Non Flame Retardant) and comes in a variety of widths in several colors. Extra-wide muslin is trypically used for creating seamless backdrops, cycloramas and projections screens.