An effective method for developing fingerprints on spent casings and ammunition. Exhibits are exposed to a solution of 50% distilled water and 50% Gun Blue by immersing the casing in the solution for approx 30 sec. Once development starts it is best to immediately rinse with distilled water to stop the reaction. Fingerprint matrix prevents gun blue from reacting with the metal, thus developing impressions.
Studies have shown that gun blue exposure is also effective post CA treatment.