Rapid and facile screening techniques to determine the effectiveness of solvents for cellulose or biomass dissolution can advance biomass processing research. Here, we report the use of a simple optical microscopy method to screen potential cellulose and lignin solvents. The described methodology was used to screen the dissolution of cellulose and lignin in two imidazolium-based ionic liquids (ILs), two phosphonium-based ILs, as well as a N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) solution in less time than other techniques. The imidazolium-based ILs and the DMAc/LiCl were found to dissolve both cellulose and lignin. Also, it was observed that one of the phosphonium-based ILs dissolved lignin and not cellulose, demonstrating a potential for biomass fractionation applications. (c) 2011 Canadian Society for Chemical Engineering