IELTS Reading: Flow-chart completion (Practice with Answers)

A loaf of supermarket bread is an engineering project timed to the minute. Flour arrives blended from dozens of farms, its protein tested and adjusted so that each batch behaves like the last. The flour is mixed with water, yeast, salt, fat and ascorbic acid, the last a legal additive in Britain since the 1950s that strengthens the gluten network and lets dough tolerate violent handling.

Where a baker gives dough hours to rise, the plant gives it minutes. High-speed mixers shear the dough while partial vacuum is applied, controlling the size of the bubbles that will become the crumb. The dough is divided, rested briefly, and shaped by machine into tins, then passes through a proving tunnel whose warmth and humidity are held to narrow limits. Proofed loaves enter an oven at around 250 degrees for twenty minutes, steam injected at the start so the crust gelatinises and sets glossy.

The finished loaf is cooled under filtered air for as long as it was baked, sliced by blades oscillating at high frequency, and bagged. The entire sequence, from flour to bag, takes under four hours; the traditional loaf it displaced took a day. What the process gained in speed it paid for in flavour, a debt the industry has been repaying with longer fermentations and sourdough starter cultures added back into the same relentless timetable.

Glass is the recyclable that forgets nothing. It can be remelted indefinitely without losing quality, and every tonne of cullet, the industry term for crushed used glass, displaces the sand, soda ash and limestone that new glass would otherwise consume.

The process begins in the home, where collection schemes ask the modest favour of colour separation, since clear, green and amber glass chemically cannot be mixed without browning the result. Collection trucks deliver to a materials facility, where the bottles pass under magnets and air jets that lift out caps and paper labels, and then over screens that sift the broken fragments from the whole.

What survives is crushed into cullet and quality-sorted, increasingly by optical machines that read the chemical tint of each fragment and flick contamination aside at speeds no human hand matches. The sorted cullet is mixed with raw materials, never alone, since some virgin material keeps the chemistry stable, and fed into the furnace at around 1,500 degrees. Melted glass flows to the forming machines that blow or press it into new containers, and the finished bottles are annealed, cooled slowly in an oven that relieves internal stress, before inspection and packing.

The loop closes unevenly. Bottle-to-bottle recycling needs the container back intact, but much collected glass arrives as shards fit only for lower uses, and the fiberglass and road-base markets that absorb them pay less than remelt. The industry's ambition is a standardised deposit scheme, which returns bottles unbroken and lifts the whole loop closer to the closed one the marketing imagines.

Paper begins as wood and becomes a mat of fibres, and the journey is mostly about removing everything that is not fibre.

Logs are debarked and chipped, then cooked in chemicals that dissolve lignin, the natural glue binding wood together, leaving a pulp of separated cellulose fibres. The spent cooking liquor, rich in dissolved wood and chemicals, is recovered and burned to power the mill, an efficiency loop the industry refined over a century.

The brown pulp is washed, bleached in stages to brightness, and refined, a mechanical squeezing and cutting between rotating blades that fibrillates the fibre surfaces so they will bond. Refined pulp, ninety-nine percent water, pours onto a moving wire mesh where most water drains, fibres interlocking as they settle into a continuous sheet. Pressed between rollers, then dried over steam-heated cylinders, the sheet reaches about five percent moisture, is smoothed in a stack of iron rolls called a calender, and is wound onto giant reels, later cut to whatever the customer buys.