The Gordon and Sweet's silver staining method is used to demonstrate reticular (retic) fibers. This method relies on the impregnation of retic fibers with silver through oxidation and reduction. The tissue is first oxidized using potassium permanganate to enhance subsequent staining. It is then sensitized using a weak ferric ammonium sulfate solution that targets and binds to the reticular fibers. The retic fibers are then impregnated by an ammoniacal silver solution that removes and replaces the sensitizer. The silver solution is reduced by 10% formalin so that a visible metallic tone highlights the retic fibers, appearing as brown or black. These brown-black deposits of metallic silver are then toned into purple-black deposits using gold chloride solution. This provides better fiber contrast and clarity than untoned sections. Unreduced silver is removed with a 5% sodium thiosulfate solution. This prevents further silver reduction by light and will also remove excess gold chloride that might still be present in the tissue section. The section is then counterstained with nuclear fast red.
