A Brief History of Natural Dyes (Mordants)
A dye is a substance that gives colour to the fabric. Usually in a way such that washing, heating or lighting does not change the colour greatly.
Dyes tend to be carbon-based (ie organic in a chemical sense) whereas pigments are very fine powders ‘dissolved’ in a liquid. Pigments generally give brighter colours and are man-made.
Dyes have existed for at least 4000 years and, before 1850, were almost entirely from natural sources such as plants, trees and lichens but also sometimes from insects. Here are some natural dyes, rarely used today, and their sources:
1. Yellow
Seeds, stems and leaves of the weld plant
The inner bark of the North American oak ‘quercetin’
Dried petals of false saffron (safflower)
2. Red
Crushed insect bodies from Coccus (cochineal) or it’s distant relation Kermes.
3. Blue
From indigo or woad
4. Purple
From the medium-sized predatory sea snail ‘commonly’ known as Murex.
5. Black
From the middle wood of the Logwood tree. This is still used today to dye silk and leather and is combined with Chromium. I have written other articles about how this ‘natural’ dye is one of the most damaging to the environment because of the use of chromium.
The art of the dye was historically a closely guarded secret with practitioners having their formulae to produce the colours and to retain them by the addition of various metal salts.
Cotton could not be directly dyed whereas wool and silk could. To add a dye to cotton the cotton had to be first treated with salts made from aluminium (red), magnesium (violet), tin, calcium (purple-red), copper, barium (blue) and iron (black-violet) and then dyed. These salts are called mordants.
The Start Of Synthetic Dyes
In the 1850s Chromium was found to give superior dye retention and so started the decline of the natural dye. Chromium mordants are still widely used for wool and less so for silk and nylon.
More precisely, the first commercially successful dye was ‘mauve’ discovered in England in 1856 and taken to market the following year. It was only sold for about 7 years but that was sufficient to start the dramatic decline of natural dyes and the investment in the science for newer and better dyes.
The Chromium discovery meshed well with the Industrial Revolution. The massively growing textile industry in Europe required a cheap and predictable manufacturing process. Natural dyes and mordants could require up to 20 steps in production, the colour could be variable and the dyes had to be transported unreliably from around the world. Because of these factors and the development of chemical science, it is easy to see how by-products of coal tar extraction & coke production, abundant in Europe, became the foundation of the modern dye industry.
By 1900 nearly 90 per cent of industrial dyes were synthetic.
Pre-war (WWI) Germany dominated the commercial dye market accounting for 90% of all output. Many German scientists worked with distilled chemicals from coal tar, an abundant by-product of the industrial revolution at the time. The German success was probably due to their investment in the scientific method and in training scientists themselves. Some further ‘by-products’ of the research include aspirin and saccharin.
After WWI the industry gravitated to Britain (ICI), the USA and Switzerland, also moving away from coal tar to petroleum-based research.
Perhaps only now with the ‘green’ movement are we seeing a resurgence of interest in natural dyes. KOTHEA cautions the environmentally-conscious reader to look carefully at claims of dyes to be natural. Whilst they may well be made from natural materials the processes used along the way can be VERY damaging to the environment.