Naphthalene Blue Black. Amido Black is a dye which stains protein present in blood to give a blue-black product. It will not detect the normal constituents of latent fingerprints, and therefore, must be used in sequence with other techniques when blood contaminated latent fingerprints are examined. It is also absorbed by some porous surfaces and may produce a high background colour. May be used in fingerprints in blood that require enhancing. Fingerprints contaminated with blood are enhanced with Amido Black by first stabilizing or fixing the blood by immersion in Methanol, usually for 1 hour. Articles are then immersed in working solution to stain the blood to a blue-black colour. This is followed by washes in Acetic Acid-Methanol solution and Acetic Acid-Distilled water solution. This treatment will take about 10 minutes. Articles are then allowed to dry at room temperature. Full use instructions are provided with the chemical.