Naphthol Blue Black, also known as Acid Black 1 or Amido Black 10B, is a textile diazo dye with high photo- and thermal-stability. It is commonly used for dyeing foodstuffs, drugs, and cosmetics. In the food industry, it is used to stain proteins on polyacrylamide gels, agarose gels, and nitrocellulose membranes during electrophoresis. After electrophoresis, fixing the proteins in the gel is recommended. The gel can then be stained with a solution of 0.1% Naphthol Blue Black in 7% (v/v) acetic acid for at least 2 hours and destained with a solution of 7% (v/v) acetic acid