The Wonderful World Of Colour
By David Donaghy
CONTENTS
The most important message of all...
We all use colour to brighten, decroate and Improve our lives - from clothing, fabrics, through cosmetics and pharmaceuticals. Much of this colour is provided by dyes. So what's the story behind these colourful substances.
Read on to find out!!!
Many natural Dyes have been known for a long time. One such dye is alizarin (i.e. Red) and Indigo, a blue dye. The best dyes came from animals - two kinds of purple were obtained from Meiterranean Shellfish and a Scarrlet red (very bright red) from Woodlice (found under old wood rotting or, sometimes, in your house!) These dyes, in biblical times, were as expensive as Gold or Silver (Ag and Au for anyone interested in perodic symbols...) and used only on the best fabrics. From the middle of the 16th century, a strong red dye was obtained from Certain Dried Mexican Beetles. This animal colour is no longer used as a dye but still in use as colouring and food and drinks, cosmetics and pharmaceuticals.
In 1856, the first synthetic dye was discovered by accident by a British Chemest named William Henry Perkin, who after his discovery, changed the face of the Dye industry and colouring in the world. Perkin in his home laboratory, was trying to make a artifical subsistute foe the drug, quinine. Perkin heated a mixture of aniline sulphate and Potassium dichromate (an oxidising agent) but instead of coming up with quinine he came up with a brown mass. He then treated this with alcohol, which made a rich purple dye, with the ability of dying silk (Thats the colour silk is usually known as). This new dye is known as Mauvine, was the first synthetic dye. Perkin then set up a production plant and founded a new branch of the chemical industry - The coal-tar industry.
After the sucess of the first dye (Mauvine) it made scientists everywhere to add an oxidising agent to aniline in the hope that it would create more colours. Edward Chambers Nicholson used arsenic (A poisionous substance - well known in the book "Arsenic and Old Lace) and produced a magneta dye named roseaniline. If you change the chemical structure of Roseaniline you get new colours).
By the late 1800's chemists everywhere tried to make new dyes. In 1858, two men, Witt and Caro made a Yellow\Orange dye (this chemical can change colour by the structure of the molecule) it was called 'AZO' dye. Half of the dyes used today are azo dyes.
In the 20th Century a man called James Morton, a carsile weaver, noticed his works of some cotton tapestries had faded after a week. Immediately he set out to find dyes that were lightfast. He found 2 dyes by 1904 - a fast yellow (flavanthrone) and a fast blue (indanthrone) both discovered by the same man. These dyes were of the anthraquinone vat range. Morton's textile business flourished but when WW1 broke out, his supplies were cut but he was determined to find out how the dyes were made - and that's what he did. His sucesses were a bright yellow, bright blue and a colourfast Green ment that the UK emerged as the biggest manufactures of dyes. Today there are now hundereds of dyes classified by their structure or medhod of application.
The way dyes stick to fabrics depends on the dye and the fibre. Protein based fibres such as silk or wool have electrostatic (static electricity) reactive parts and create bonds with the dyes. Cellouse-based fibres such as cotton or linen stick weakly by electrostatic bonds. Often fixing agents (Mordants) is needed to stick the dye and fabric together.The salts of metals are used (e.g. chromium IV). The use of mordants increase the colour range of dyes. See the table below!
| Dye | Result With Mordant |
| Ailzarin | Violet |
| Chronium | Brown-Violet |
| Calcium | Purple-Red |
| Aluminium | Rose |
The past decades have seen a dramatic interest in dye chemistry. Dyes are in great demand for all kinds of applications - not all related to colour! They are used in flouresent colours, in lasers LCD displays (liquid crystal displays), in recording systems such as laser recording discs and information storage systems.
Article By David Donaghy 11E: Loreto College, Coleraine.
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