IELTS Academic Reading Practice Test 102

Stained glass has been used in windows for at least 1,700 years. Fragments of coloured window glass have been found in Roman villas, and some early Christian texts mention glazed openings that admitted light while giving privacy. For centuries, however, the making of coloured glass remained a small craft, and it was only when churches began to be built with large window openings that stained glass developed into a major art form.

The basic material is produced by adding metallic oxides to molten glass. Cobalt gives a deep blue, copper can produce a red or a green depending on the firing conditions, and manganese yields purple. Medieval glass was often coloured right through its thickness, a type known as pot metal glass. Because such glass could be too dark to show detail, glaziers also painted the surface with a mixture of ground glass and iron oxide, which was then fused to the glass in a kiln. This allowed faces, folds in drapery and lettering to be drawn with considerable precision.

A medieval window was made in a workshop, usually under the eye of a master glazier. First a full-size design, known as a cartoon, was drawn on a board or table. The glazier selected pieces of coloured glass, cut them to shape with a heated iron or a grozing iron, and painted the details. The pieces were then set into grooved lead strips called cames, which were soldered together at the joins. A putty was often pressed into the gaps to make the window weatherproof and to stop the glass from rattling in the wind.

The great age of stained glass began in the twelfth century, when builders in northern Europe constructed churches whose walls seem to be made largely of windows. The coloured light was intended not only to beautify the building but to teach Bible stories and the lives of saints to people who could not read. A window was a visual sermon, and for this reason such windows have sometimes been called the poor person's Bible.

The colours available to medieval glaziers were rich but limited. Blue was often the most prized, and the blue of the windows of Chartres Cathedral in France became so admired that the name Chartres blue is still used. Red was especially difficult to produce because copper red glass had to be cooled and reheated under precise conditions, and even then the colour could be uneven. After about 1300 a major innovation appeared: painting a compound of silver onto the surface of the glass produced a clear yellow stain, which allowed glaziers to add crowns, hair and other small details without cutting extra pieces.

In the later Middle Ages, new methods changed the appearance of windows. Glass painters increasingly covered large areas of coloured glass with paint and used silver stain more freely. At the same time the glass itself became thinner and more transparent, so windows gradually looked less like jewelled walls and more like bright pictures. Wealthy patrons also began to donate windows that showed their own portraits kneeling in the corners.

The Renaissance brought a different fashion. Artists influenced by painting wanted to show perspective and natural light, and coloured glass was often replaced by large clear panes with painted scenes in muted enamel colours. Stained glass also suffered repeatedly from war, religious conflict and neglect. In England, for example, many medieval windows were destroyed during the Reformation in the sixteenth century and by later Puritan iconoclasm. Surviving windows were sometimes repaired by glaziers who simply pieced broken fragments together in random patterns, giving some old windows a patchwork appearance.

By the eighteenth century, stained glass had fallen so far out of fashion that the skills needed to make traditional coloured glass had largely disappeared. A revival began in the nineteenth century, partly because architects returned to the Gothic style and wanted windows in keeping with it. Makers tried to recover the techniques of the medieval craftsmen, and new studios were founded across Britain and continental Europe. Restoring old windows became a discipline in itself, though some restorations were criticised for replacing missing sections with glass that did not match.

The revival was followed by a period of experiment. In America, Louis Comfort Tiffany and John La Farge independently developed opalescent glass, which contains internal impurities that scatter light and give a milky, streaky appearance. Tiffany also popularised the copper foil method, in which each piece of glass is wrapped in thin copper before being soldered, allowing much finer lines than traditional lead cames. These techniques were used for lamps, windows and decorative panels.

Today stained glass is found not only in churches but in public buildings, restaurants and homes. Conservation has become an important scientific task: environmental monitors are placed on windows to measure condensation, temperature and air flow, and damaged panels are documented in detail before any treatment. At the same time, modern artists continue to use the medium, sometimes with abstract compositions and sometimes with narrative scenes. The craft thus combines materials and methods that are centuries old with new concerns about preservation and design.

Seawater is naturally slightly alkaline, with a modern surface pH of about 8.1. When carbon dioxide from the atmosphere dissolves into the ocean, part of it reacts with water to form a weak acid called carbonic acid. This acid quickly separates, releasing hydrogen ions and bicarbonate ions. The added hydrogen ions make the ocean more acidic, a process known as ocean acidification. Since the start of the industrial era, the average pH of the ocean surface is estimated to have fallen by about 0.1 units, which represents roughly a 30 per cent increase in acidity. This does not mean the ocean is about to become an acid, but it is moving towards chemical neutrality.

The main source of the extra carbon dioxide is the burning of fossil fuels, with additional contributions from cement manufacture and land clearing. Approximately a quarter of the carbon dioxide released by these human activities is taken up by the ocean, where it is stored for decades to centuries. In many ways this uptake is beneficial, because it slows the rise of carbon dioxide in the atmosphere and thereby reduces the speed of global warming. The benefit, however, comes at a chemical cost to the sea.

The extra hydrogen ions do not remain free. Many of them combine with carbonate ions that are already present in seawater, converting them into bicarbonate. As a result, the concentration of carbonate ions falls. Marine organisms that build shells and skeletons usually need carbonate ions together with dissolved calcium to produce calcium carbonate. When carbonate ions become scarce, the construction of calcium carbonate becomes more difficult, and existing structures may begin to dissolve. Scientists often measure the saturation state of aragonite and calcite, the two common forms of calcium carbonate, to judge the risk to marine life.

Some of the organisms most directly affected are corals, molluscs, sea urchins and certain plankton. Pteropods, small swimming snails sometimes called sea butterflies, have thin shells made of aragonite, a form of calcium carbonate that is especially soluble. In waters that are undersaturated with aragonite, their shells can begin to dissolve within days or weeks. Coccolithophores, single-celled algae covered with ornate calcium carbonate plates, also face energetic costs in maintaining their coverings. Even organisms that do not form shells can be affected indirectly, because many fish depend on shelled plankton for food. Sea urchins and many molluscs also rely on calcium carbonate for their shells or internal structures, and laboratory experiments have found that some grow more slowly and produce weaker material when carbonate concentrations are reduced. Larval stages are often the most vulnerable, because their first skeletons must be produced quickly when carbonate ions are scarce.

Coral reefs are threatened by more than acidification alone. Rising sea temperatures cause bleaching, in which corals expel the symbiotic algae that provide much of their energy. Acidification adds a further burden: laboratory and field studies have shown that calcification rates decline as pH falls, and the skeletons that are produced may be weaker and more easily eroded by waves and boring animals. The combined effects are likely to reduce reef growth and make reefs more vulnerable to storms.

Economic harm has already been reported. Along the Pacific coast of North America, acidic water welling up from the deep ocean has been linked to failures in oyster hatcheries, where larvae failed to form their first shells. The events were complex and involved natural upwelling, but the lower pH of the water made the problem worse. Similar difficulties could affect aquaculture of mussels and clams, and the fishing communities that depend on them. In the first decade of the 2000s, these episodes became an early warning of how acidification can interact with local conditions. Hatchery operators responded by monitoring water chemistry and treating incoming seawater, and some of these interventions improved larval survival.

Ocean acidification does not proceed at the same rate everywhere. Cold water absorbs carbon dioxide more readily than warm water, so polar seas acidify more quickly. Upwelling regions, where deep water rich in carbon dioxide rises to the surface, also experience periods of especially low pH. Coastal waters receive further inputs from rivers carrying nutrients, and the breakdown of excess organic matter can add carbon dioxide locally. Models project that Arctic surface waters may become undersaturated with aragonite for parts of the year within a few decades, placing local species under stress even before the global average reaches similar conditions. Instruments have already recorded aragonite saturation values below 1, the threshold at which seawater becomes corrosive to unprotected shells, during parts of the year in the Arctic Ocean.

Responses to acidification fall into two broad categories. The first is to reduce the amount of carbon dioxide entering the atmosphere, for example by shifting energy systems away from fossil fuels. The second is to help marine life cope, through monitoring, selective breeding of aquaculture species that tolerate lower pH, and protecting areas where local conditions are less affected. Researchers stress that local action alone cannot stop a global change, but it can reduce pressure while more far-reaching measures are introduced. International programmes coordinate measurements across ocean basins, producing the data needed for management decisions.

Few issues in school policy provoke such predictable argument as the uniform. Supporters claim that it makes schools calmer, fairer and more orderly; opponents dismiss it as an outdated restriction on personal expression. In my view, the uniform itself is less important than the way the policy is designed and the school culture around it. A school can have identical blazers and ties and still fail to foster respect, or it can have a loose dress code and a strong sense of community.

The most common justifications for uniform are that it improves discipline, reduces bullying, creates a sense of belonging and removes competition over clothing. These claims appeal to common sense, and they are repeated in school brochures and by politicians. Common sense, however, has often proved a poor guide in education. The benefits sound reasonable, but they need to be weighed against evidence, which is far less clear than the confidence of the claims might suggest.

When researchers have looked at academic outcomes, the results are generally disappointing for uniform advocates. Several large reviews have found no consistent association between wearing a uniform and better test scores or rates of school completion. Some studies report small improvements in attendance or in the orderliness of corridors, but these effects are not found everywhere and may result from other changes introduced at the same time. The difficulty is that schools that adopt uniforms often introduce new behaviour policies, additional staffing or new leadership at the same time, making cause and effect hard to separate. In short, there is little reliable evidence that uniform raises achievement.

The equity argument is similarly double-edged. Uniforms can indeed hide the most visible markers of family income, so that a child whose parents cannot afford designer labels is not immediately marked out. Yet uniform itself costs money, and for a low-income family the cost of a blazer, trousers, skirt and shoes bought from an approved supplier can be a heavy burden. Second-hand schemes and grants can help, but only if they are well publicised and do not create stigma of their own. In some systems, parents report spending a considerable sum each year on items that children quickly outgrow.

Uniform also sits awkwardly with the task of helping young people develop their own identity. Adolescents, in particular, use clothing to experiment with how they present themselves to the world. A dress code that is too rigid may push that experimentation into other areas, such as hairstyles, jewellery or the way a shirt is tucked. It may also teach pupils that compliance matters more than judgement. Schools that allow some choice within a framework often report that students are more willing to accept the rules. Psychologists note that identity formation is a central task of the teenage years, and clothing is one of its visible tools.

On discipline, the evidence is particularly weak. A school that insists on identical ties and polished shoes may still have poor behaviour if relationships and teaching are weak. Equally, a school with no uniform can be calm and orderly because it invests in clear expectations and consistent supervision. Studies comparing schools with and without uniforms have not shown that the presence of a uniform, by itself, reduces bullying or serious misbehaviour. International comparisons are of limited help, because school cultures, legal frameworks and methods of discipline differ too much.

What, then, should a school do? The answer, I believe, is to treat uniform as one small part of a wider culture. A policy is more likely to be accepted if it is developed with parents and pupils, if the required items are affordable and comfortable, and if the rule is enforced calmly rather than punitively. Consultation with families tends to produce rules that are seen as fair. Schools should also ask whether the uniform supports learning or merely signals tradition. For example, a synthetic blazer that is too hot in summer may hurt concentration more than it aids discipline.

Where uniform does seem to help is in reducing the daily negotiation over what to wear. Many families report that mornings are easier when there is no debate about whether an outfit is suitable, and some pupils say they feel less exposed to teasing about clothes. A uniform that is comfortable and fairly enforced can contribute to a positive school climate. Reducing morning stress is one of the clearest day-to-day benefits. These are real benefits, but they are modest. They do not justify the stronger claim that uniform transforms academic standards, and they do not mean every school must adopt one.

Overall, I would defend a school's right to have a uniform, provided the policy is thoughtful and inclusive. I would also defend a school's right to dispense with one, if its staff and community prefer a different approach. The strongest evidence suggests that what matters most is not the garment but the quality of teaching, the consistency of expectations and the relationships between staff and students. Uniform cannot substitute for those things, and it should not be treated as if it could.