gram method

(noun) a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram's solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the gentian violet are Gram-positive and those that do not retain it are Gram-negative. Synonyms: Gram's method, Gram method, Gram's procedure, Gram's stain, Gram stain.