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
(intro) - Azurite - Cerulean Blue - Cobalt blue - Egyptian blue - Indigo - Prussian blue - Smalt - Ultramarine