Amido black 10B is an amino acid staining azo dye used in biochemical research to stain for total protein on transferred membrane blots, such as the western blot.[1] It is also used in criminal investigations to detect blood present with latent fingerprints - it stains the proteins in blood a blue-black color.[2] Amido Black can be either methanol or water based as it readily dissolves in both. With picric acid, in a van Gieson procedure, it can be used to stain collagen and reticulin.