The addition of the alcohol iso-butanol (2-methylpropan-1-ol) to water was found to improve the post-staining procedures for semi-thin and ultrathin resin sections, for both light and electron microscopy. Stain penetration was enhanced with samples embedded in both acrylic and epoxy resins and provided structural information not previously seen. These improvements were found with general (non-specific) stains and a fluorescence stain for light microscopy, as well as for a range of heavy metal stains for electron microscopy. The use of this water/solvent medium also gave improved results when used in a variety of immunogold labelling procedures, resulting in a greater specific label density without affecting background gold levels. The use of this solvent/water medium may have wider applications for other types of staining.