The present invention relates to improved specific binding assay methods, kits and devices utilizing chromatographically mobile specific binding reagents labelled with colloidal particles. Specific binding reagents labelled with colloidal particles such as gold and selenium may be subjected to rapid chromatographic solvent transport on chromatographic media by means of selected solvents and chromatographic transport facilitating agents. Further, impregnation of solid substrate materials with labile protein materials including colloidal particle and enzyme labelled reagents in the presence of meta-soluble proteins provides for the rapid resolubilization of such materials which have been dried onto such substrate materials.