雅思阅读第096套P1-The Search for Colour

The Search for Colour

We seldom reflect on the artificial colour of modern merchandise. A blue car is blue; a red chair, red; a green bicycle, green. But why does it have colour? Answer, because its surface contains pigment. If this was originally dissolved in a carrier liquid to transfer the colour, it is known as a dye, but whatever the case, since colour is the most visible element in all objects we desire, pigments can be said to be the basis of customer choice, and therefore of almost all hard trade and transactions. Consequently, production of this substance is big business, now accounting for over twenty billion dollars annually in global sales—yet there was a time when none of it existed.

Going back into the mists of prehistory, objects, tools, and clothing were all earthen and bland, without anything except their natural colours. The first pigments used were of mineral origin — from natural clays tinted by the presence of iron-oxides. The best known examples are the gold colour of ochre, the brown of umber, and the yellow of sienna. These were ground up and mixed with fat to create paint, used, for example, in the earliest European cave paintings. Ash, as well as charcoal (derived from heating wood in the absence of oxygen), were also used to provide black, but in the search for colour, it was soon discovered that biological matter, such as plants, animal waste, mollusks, and insects, could yield more interesting results.

Crimson —a bright red colour—is a good example. It was extracted from kermes, a small insect found on Southern-European oak trees. The pigment is a constituent of the carminic acid produced inside the creature’s body, used to discourage predation by birds or other insects. However, with the trees being large and bushy, and the sap-feeding insects few and far between, pigment production was a meticulous and time-consuming process. This increased the price of the product, the end result being that, in Northern Europe, pure crimson long remained a luxury colour for clothing and textiles.

Interestingly, across the Pacific Ocean, people were producing the same colour from the same chemical within another insect. They were called cochineals: small scaly creatures which breed in abundant clusters on the fleshy leaves of a commonly occurring cactus. These insects have many advantages over kermes. Being so prolific and so easily seen by predators, they need to produce higher concentrations of carminic acid for protection, up to a quarter of their body weight. The pigment which results is also stronger and longer-lasting. Finally, the insects are far more easily obtained, being simply scrapped or knocked off the cactus leaves, Thus, after the Spanish conquest of Mexico, cochineals replaced kermes almost completely, becoming a lucrative Central American export for the next few centuries.

The lure of crimson was only exceeded by the vivid ‘Tyrian purple’ — a colour which had ranked in highest favour since antiquity. Its source was the medium-sized Murex sea snail. With a range around the coastal Mediterranean, early civilisations there soon realised that the mucus the snail secretes when poked and prodded could be treated to produce a purplish-blue dye which did not fade with time. However, by needing thousands of sea snails and using a complicated (and still little known) process, all for the production of only small amounts of pigment, the colour was so expensive it could only be afforded by the ruling classes. This led to purple becoming associated with royalty. Roman emperors traditionally wore clothing of this colour.

For a less durable blue, suitable for dyeing clothes, the indigo plant was discovered. Its leaves were fermented, and then left to age, and the sediment eventually produced was dried, treated, then reduced to a blue powder. This pigment can, in fact, be said to be the oldest used to colour fabric. It is one reason jeans were originally blue, and remain so to this day, indigo being the dye used to colour them. However, it was not suitable for painting or artistic purposes. For that, European artists used a mixture derived from the grinding up of lapis lazuli, a semi-precious stone, whose only known source was in far Afghanistan. Consequently, this colour was very costly, and many artists avoided it altogether. Others, however, were deliberately extravagant in its use, producing proportionally more expensive paintings.

The cost of this paint resulted in much experimentation during the Industrial Revolution in search of chemical-based alternatives. This eventually led to the first modern synthetic pigment, Prussian Blue. Discovered in Germany in the early 18^thcentury, it was put into rapid production and exportation, giving artists around the world the first cheap, yet stable, blue pigment. Other chemists were making similar breakthroughs. The vivid purple of the Murex snail was accidentally produced by an English chemist, William Perkins, who soon put ‘mauveine’ into commercial production. With such efforts, affordable pigments were soon found in all colours.

Mass production followed, bringing industrial prosperity to Northern Europe, but decline in many parts of the world where traditional organic pigments were still under production. In the Americas, for example, the crimson of cochineals, having long been a Spanish monopoly and rich source of export income, went into steady decline. However, all was not lost. In this modern age, there has been a shift back towards naturalness, even in pigments, and this has seen a resurgence in the popularity of cochineals. The pigment is now commercially produced in several countries, with Peru being the largest exporter.

SECTION 1: QUESTIONS 1-13

Questions 1-4

Complete the sentences.

Choose NO MORE THAN TWO WORDS from the passage for each answer.

Ultimately, pigments are important because they are so 1 _________________.

Umber and sienna are examples of 2 _________________

Originally, more unusual colours were derived from 3 _________________

Generally, predators of insects do not like the taste of 4 _________________

Questions 5-8

Do the following statements agree with the information given in Reading Passage One?

Write

5 _________________ Kermes were easy to collect.

6 _________________ Kermes produce better pigment than cochineals.

7 _________________ Kermes are bigger than cochineals.

8 _________________ Cochineals are still a valuable crop.

Questions 9-13

Complete the summary of the second half of the passage.

Choose ONE WORD from the passage for each answer.