Troubleshooting the Grocott Methenamine Silver (GMS) Stain

Problem

Proper Technique

impure water (tap, other)

ultrapure water

dirty glassware

clean then acid-washed glassware; make sure slides are clean

concentration of chromic acid too low (from repeated reuse) or too high

use the correct concentration of chromic acid

lower quality silver nitrate

use better grades of silver nitrate

decomposition of methenamine

store powder in cool, dry place; store solutions in a dark bottle in the refrigrator; discard if there is a change in appearance

temperature of reagents too low

bring all solutions to room temperature before use

temperature during incubation uneven

incubate in a water bath kept at constant level 56-60°C

sodium thiosulfate step omitted or solution dilute

failure to perform properly will result in appearance of a black precipitate with time

too much or too little counterstain

counterstain properly

deterioration in the gold chloride solution due to repeated reuse

avoid solution that is a pale yellow or that has a brownish precipitate; either use fresh solution or filter then spike with fresh reagent

use of fingers or metal forceps to handle slides

use clean, plastic forceps or wear unpowdered gloves

failure to add borate to silver solution

borate raises the pH to alkaline levels

time at each step too long or too short

time each step carefully