# The Revival of Natural Indigo Dye IELTS Academic Reading - 13 questions - 20 minutes - True / False / Not Given, Note completion Source: Written by Testmigo. ## The passage You should spend about 20 minutes on Questions 1-13, which are based on the passage below. Almost every pair of blue jeans owes its colour to indigo, one of the oldest dyes in existence. The earliest fabric known to have been coloured with it is a scrap of woven cotton from Huaca Prieta, an archaeological site on the northern coast of Peru in South America, and it is around 6,000 years old. That is roughly 1,600 years earlier than the first indigo-dyed cloth from Egypt. Today, however, nearly all of the world's indigo is made in factories rather than taken from plants, and the people who still work with the natural dye form a small but growing group. Indigo is unusual because it does not come from a single plant. Several unrelated groups of plants, growing in very different climates, contain the substances needed to make it. In tropical Asia the main source was a shrub called Indigofera, European dyers relied on a plant known as woad, and in East Asia a type of knotweed was widely grown. Although these plants look nothing alike, the blue they yield is chemically identical, so nobody can tell from a dyed object which plant was used. The name of the dye, on the other hand, points to one country: it comes from the Latin word indicum, meaning 'Indian', because India was an early exporter. Getting the colour out of the plant is a surprising process, since fresh indigo leaves are green and show no sign of blue. They contain a colourless compound called indican. When cut leaves are pressed into a tank of water and left to ferment for twelve to fifteen hours, the indican breaks down and releases a substance called indoxyl. The leaves are then taken out, and lime is stirred in to make the liquid alkaline. Next, the yellow-green liquid has to be beaten so that oxygen can get into it. Photographs of indigo works in nineteenth-century India show dozens of men standing in enormous tanks, churning the mixture with their legs, and a blue foam often appears on the surface at this stage. The newly formed dye sinks to the bottom as a paste, which can be dried into cakes that are easy to store and carry. Putting the colour onto cloth requires another chemical trick, because indigo does not dissolve in water. Dyers therefore keep it in a warm, alkaline vat, where it becomes soluble for a time. The liquid in the vat looks yellowish-green rather than blue, and so does a piece of fabric when it is first lifted out. Once it is exposed to the air, however, the fabric turns blue. A pale shade needs only a few short dips, but a deep blue needs many longer dips, each one followed by time in the open. For centuries indigo was such a valuable product that it was known as 'blue gold', but its value had a darker side. In Europe, woad growers fought hard against imported indigo, while colonial powers set up indigo plantations in Asia and the Americas, where local people and enslaved Africans were forced to work. Throughout the nineteenth century, India was a major supplier of the natural dye to Western markets. At the same time, chemists in Germany were trying to make it artificially. Adolf von Baeyer first produced indigo in a laboratory in 1878, and when he patented his method in 1880, the chemical company BASF obtained the rights to use it. BASF invested 18 million gold marks in research, as much as its entire share capital at the time, and only in 1897 did it launch a synthetic indigo that could be sold commercially. The new product was both cheaper and purer than plant indigo, and growers suffered badly. In 1897 about 19,000 tonnes of indigo were produced from plants, but by 1914 the figure had fallen to roughly 1,000 tonnes. Planters in India paid for laboratory experiments designed to increase yields and reduce costs, yet this research did not win back their customers. Factory-made indigo still dominates: by 2011 about 50,000 tonnes were being made every year, and 95 per cent of it was used for denim. The synthetic dye has an environmental cost. It is made from aniline, a toxic chemical obtained from benzene, and its manufacture involves hazardous substances such as formaldehyde and hydrogen cyanide. Mills usually dissolve indigo with sodium dithionite, which breaks down into compounds that can corrode the pipes in dye works and wastewater plants. These concerns, together with new respect for traditional knowledge, have encouraged a revival. Experts say that the small impurities in plant indigo give fabric a distinctive character, and some artisans say they miss the earthy smell of a natural vat. In Tokushima, Japan, craftspeople still pile dried leaves in a building known as a 'bed' and ferment them for about 100 days. In the United States, a company in Tennessee grows indigo on around 150 acres and sells the dye to the denim industry. It has also developed a device that measures how much dye the leaves contain while they are still in the field. ## Questions ### Questions 1-7: True / False / Not Given Do the following statements agree with the information given in the passage? Choose TRUE if the statement agrees with the information, FALSE if the statement contradicts the information, or NOT GIVEN if there is no information on this. 1. The oldest known piece of indigo-dyed cloth was discovered in South America. 2. The blue obtained from woad is chemically different from the blue obtained from Indigofera. 3. Adolf von Baeyer became wealthy as a result of his indigo patent. 4. When it first went on sale, BASF's indigo cost less than indigo made from plants. 5. Research paid for by planters in India helped natural indigo to remain competitive. 6. Most of the indigo manufactured in factories is used to colour denim. 7. Natural indigo dyers believe that synthetic indigo fades more quickly. ### Questions 8-13: Note completion Complete the notes below. Choose ONE WORD ONLY from the passage for each answer. Making and using natural indigo Extracting the dye - cut leaves are kept in water so that they **(8)** _____ (12-15 hours) - **(9)** _____ is added to reduce the liquid's acidity - the liquid is beaten: in India, workers once used their **(10)** _____ to do this - a blue **(11)** _____ may be seen on top of the liquid - the dye settles as a paste, then is dried into **(12)** _____ for storage and transport Dyeing - fabric is yellowish-green when removed from the vat, then turns blue - for a dark shade, the fabric needs a large number of **(13)** _____ [Practice online with a timer and instant marking](https://testmigo.com/ielts/reading/the-revival-of-natural-indigo-dye) - [Answers and explanations](https://testmigo.com/ielts/reading/the-revival-of-natural-indigo-dye/answers)