Indigotine Blue

Dyestuff for lacquers and wood stains. Food coloring E 132. Indigocarmine used to be produced by heating indigo in pots together with sulfuric acid. Sulfonated indigo is water-soluble and was used for dyeing or making inks, but its lightfastness is lower than that of indigo. Today, this dye is made from synthetic indigo and is used as an indicator dye and food colorant.