Methods for characterizing a nanotube formulation with respect to one or more particular ionic species are disclosed. Within the methods of the present disclosure, this characterization provides control over the surface roughness (or smoothness) and the degree of rafting within a nanotube fabric formed from such a nanotube formulation. In one aspect, the present disclosure provides a nanotube formulation roughness curve (and methods for generating such a curve) that can be used to select a utilizable range of ionic species concentration levels that will provide a nanotube fabric with a desired surface roughness (or smoothness) and degree of rafting. In some aspects of the present disclosure, such a nanotube formulation roughness curve can be used adjust nanotube formulation prior to a nanotube formulation deposition process to provide nanotube fabrics that are relatively smooth with a low degree of rafting.