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1.  Overview     2. History of use     3. Making the pigment     4. Technical details

How Indigo is made:          Source: Plants: woad (Isatis tinctoria L.), Indigofera tinctoria L. and others Natural variety of pigment To prepare the dye, freshly cut plants were soaked until soft, packed into vats and left to ferment. It was then pressed into cakes for use as a watercolor or dried and ground into a fine powder for use as an oil paint.. In the lab Materials needed: o-Nitrobenzaldehyde, acetone, sodium hydroxide Safety (MSDSs): o-Nitrobenzaldehyde (at Stanford University), acetone, sodium hydroxide (at Fisher Scientific) Method: 4 g o-nitrobenzaldehyde is dissolved in 40 ml acetone using a 200 ml erlenmeyer flask. 20 ml deionized water are then added and the flask is shaken thoroughly. Next, 16 ml of a 1 molar solution of sodium hydroxide is added slowly. The mixture is stirred with a glas rod and left standing for five minutes. The precipitated indigo is then filtered off and dried at room temperature.

Illustration of the process:             Making indigo in the laboratory   The ground pigment:             Pile of ground Indigo:

Other blues         (intro) - Azurite - Cerulean Blue - cobalt blue - Egyptian blue - Indigo       Prussian blue - smalt - Ultramarine