General video · Level C1 - Part 2

How It's Made Fireworks

What's a Fourth of July celebration without fireworks? Brilliant colors exploding in the air.

Level: C1 · 60 sentences

Transcript

1. What's a Fourth of July celebration without fireworks?
2. Brilliant colors exploding in the air.
3. The oohs and ahs they elicit on the ground.
4. Fireworks are so high-tech these days.
5. It's easy to forget they're not a modern invention.
6. Historians believe gunpowder, the explosive ingredient in fireworks,
7. was invented in China around 1000 A.D.
8. It's said that in a famous battle, the Chinese emperor illuminated the sky with it,
9. scaring away the enemy.
10. During the Renaissance, the Europeans invented the type of fireworks we know today.
11. Modern pyrotechnicians use computers to ignite fireworks from a safe distance.
12. And to synchronize their bursts with music.
13. Assembling explosives into fireworks is the job of the pyrotechnician.
14. Even the tiniest spark of static electricity could set them off.
15. So anti-static gloves are a must.
16. A firework is made up of separate compartments within a shell.
17. The burning fuse explodes one compartment at a time.
18. Creating those staggered bursts in the sky.
19. The pyrotechnician first glues the main fuse into the bottom of the shell.
20. The glue is naturally colorless;
21. it is dyed blue so he can tell exactly where he's applying it.
22. He puts the bottom aside to work on the second compartment of this two-compartment firework.
23. He starts by spooning a powdered explosive into the center.
24. Then he caps it;
25. here he's working on two fireworks at a time.
26. Next step: a brown cardboard shock absorber
27. to shield this compartment from the first compartment's explosion.
28. Then a corrugated cardboard disc and a plastic spacer.
29. It'll take the fuse one and a half seconds to burn through these two components.
30. Creating a slight delay between the first explosion and the second.
31. Gluing the second compartment together is tricky.
32. If it's too tight, it'll stifle the explosion,
33. but it has to be tight enough to withstand the delay.
34. With the second compartment done, it's time to prepare the first.
35. He glues a sleeve onto a case.
36. Then fills it with hundreds of stars.
37. Stars are what create the flashes of color.
38. They're carefully measured explosives mixed with coloring agents.
39. Such as magnesium for white, copper salts for blue,
40. and charcoal for orange.
41. The pyrotechnician must handle them gingerly, or they could detonate.
42. Next, he adds comets, another type of exploding decoration.
43. He tops it off with gunpowder.
44. Finally, he glues the two compartments together.
45. Filling the remaining space with the same combination of ingredients.
46. Once the shell is full, he glues on the cover.
47. And the tighter the better;
48. the more pressure that builds up, the bigger and more spectacular the explosion.
49. Next, he wraps the fireworks in kraft paper.
50. The label uses international color codes to indicate the size of the shell.
51. The lift charge, a gunpowder bag with a long fast-action fuse, goes at the base of the shell.
52. That's what will send the firework into the sky.
53. When they light the main fuse at the top,
54. it simultaneously lights two secondary fuses.
55. The time-delay fuse inside the shell, running through the compartments of explosives.
56. And that long fuse running along the outside down to the lift charge at the base.
57. Once the lift charge ignites,
58. heat and gas build up inside the launch tube until they explode.
59. Propelling the firework close to 1,000 feet skyward.
60. Let the light show begin.