The invention relates to a film comprising greater than 80 wt % single-wall carbon nanotubes wherein the tensile modulus is at least about 6 GPa at 0.2% strain and the conductivity of the film is at least about 70,000 S/m. The tensile modulus is typically about 8 GPa at 0.2% strain. The method for making the film comprises preparing a solution of single-wall carbon nanotubes in a superacid, such as oleum containing approximately 20 to 30% sulfur trioxide, under a dry, oxygen-free atmosphere. The solution is placed on a surface in a moisture-containing atmosphere, wherein the solution absorbs moisture and acid leaches out. The film is washed to further remove acid, dried, and, optionally, subjected to a heat treatment. Besides free-standing films, coatings of single-wall carbon nanotubes can be made on a variety of surfaces including polymers, glass, metals, and ceramics. The surfaces can be flat planes, fibers or contour shapes.