Vegetable Indigo

Dark-blue, light pieces, which, on being rubbed with a horn spoon, or other hard substances, exhibit a coppery metallic luster. Good vegetable indigo has a lower specific gravity than water, hence it floats on the latter. It should contain at least 60 per cent of indigo blue. 

The colouring matter may be an artificial organic dye or a vegetable colour (extracts of dye wood or of other parts of plants, indigo) or an animal colour (cochineal) lakes are also made with mixtures of several colouring matters. 

Certain vegetable colouring matters, such as alizarin (from madder) and indigo, are now prepared artificially and are hence considered both as natural and as artificial organic dyes. 

Vegetable materials such as henna (flowers and leaves of Lawsonia in-ermis that contain acidic naphthoquinone, chamomile, and indigo)... 

Henna. Henna is the oldest and most widely used vegetable dye utilized in hair coloring. A temporary chestnut color is produced in blond or auburn hair by applying a paste of henna flowers and leaves ground in hot water immediately before use. (The dye is unstable in aqueous solution.) The addition of indigo achieves darker blue-black shades extracts of walnut shell or logwood enhance brown coloration. 

Some views do not distinguish between Tyrian and hyacinthine purples, whereas others contend that hyacinthine purple is the vegetable dye indigo. The sources of this confusion are discussed in the following paragraphs. 

Only a few natural dyestuffs (indigo, alizarin, and purpurin) have been prepared synthetically, but the number of artificial dyestuffs is very large. Some of these, especially the phthalei ns and rosolic acid, seem to approach the natural dyestuffs in constitution, but the greater number belong to special classes, which are without analogue in either the animal or the vegetable kingdom. 

Like most ammonium bases, methylene blue does not dye wool easily, but is readily fixed on silk and tannined cotton. It has also a slight affinity for unmordanted vegetable fibres. Methylene blue is principally used in cotton-dyeing. It dyes a greenish shade of blue, which shows a dull tone similar to that of indigo. It is very fast to light, and the shades may be readily modified by other basic dyestuffs, such as methyl violet or malachite-green. 

Vegetal Blue The blue or purple color indigo is commonly derived from a plant... 

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