1 00:00:01,333 --> 00:00:03,933 ♪ ♪ 2 00:00:07,000 --> 00:00:11,000 NARRATOR: Notre-Dame de Paris. 3 00:00:11,000 --> 00:00:13,400 A treasured icon of Gothic architecture 4 00:00:13,400 --> 00:00:15,033 and medieval construction. 5 00:00:16,066 --> 00:00:18,133 ELSIE OWUSU: The level of determination 6 00:00:18,133 --> 00:00:20,633 and the feat of engineering in those days, 7 00:00:20,633 --> 00:00:21,800 just extraordinary. 8 00:00:21,800 --> 00:00:25,500 NARRATOR: But on April 15, 2019, 9 00:00:25,500 --> 00:00:28,033 disaster strikes. 10 00:00:28,033 --> 00:00:30,300 A huge fire rips through the cathedral... 11 00:00:30,300 --> 00:00:33,433 (people exclaiming) 12 00:00:33,433 --> 00:00:36,633 NARRATOR: ...threatening to bring down the entire structure. 13 00:00:36,633 --> 00:00:38,000 (revving) 14 00:00:38,000 --> 00:00:42,066 ♪ ♪ 15 00:00:42,066 --> 00:00:45,200 Now, master craftspeople and engineers 16 00:00:45,200 --> 00:00:49,666 battle to bring Notre-Dame back to life. 17 00:00:49,666 --> 00:00:51,966 PHILIPPE VILLENEUVE (translated): From what we've done so far, 18 00:00:51,966 --> 00:00:54,433 it's clear to us that this cathedral will be extraordinary. 19 00:00:54,433 --> 00:00:58,700 NARRATOR: Hundreds of workers are in an ambitious race 20 00:00:58,700 --> 00:01:00,566 to restore this medieval masterpiece 21 00:01:00,566 --> 00:01:04,666 in time for a grand reopening planned for 2024. 22 00:01:06,933 --> 00:01:08,566 (speaking French): 23 00:01:09,900 --> 00:01:13,200 NARRATOR: Historians and scientists work together to analyze 24 00:01:13,200 --> 00:01:17,066 and reproduce Notre-Dame's architectural mysteries. 25 00:01:17,066 --> 00:01:18,433 KARINE BOULANGER: It is a very unique opportunity. 26 00:01:18,433 --> 00:01:20,300 It's a kind of a 27 00:01:20,300 --> 00:01:21,733 walking backwards in time. 28 00:01:21,733 --> 00:01:24,100 ♪ ♪ 29 00:01:24,100 --> 00:01:27,700 NARRATOR: They're revealing ancient technology hidden for centuries. 30 00:01:27,700 --> 00:01:29,933 MAXIME L'HÉRITIER: We're dealing with unknown structures 31 00:01:29,933 --> 00:01:33,733 that are, so far, unique in Gothic architecture. 32 00:01:33,733 --> 00:01:35,566 NARRATOR: And struggling to save 33 00:01:35,566 --> 00:01:37,033 the fragile structure of the building. 34 00:01:37,033 --> 00:01:38,800 JEAN-DIDIER MERTZ: The loss of matter 35 00:01:38,800 --> 00:01:40,700 is catastrophic for us. 36 00:01:40,700 --> 00:01:43,966 NARRATOR: Now, three years into this extraordinary 37 00:01:43,966 --> 00:01:46,200 five-year restoration project, 38 00:01:46,200 --> 00:01:50,000 can this team meet its ambitious deadline? 39 00:01:50,000 --> 00:01:51,933 "Rebuilding Notre-Dame," 40 00:01:51,933 --> 00:01:53,900 right now, on "NOVA." 41 00:01:53,900 --> 00:02:14,000 ♪ ♪ 42 00:02:14,433 --> 00:02:19,300 ♪ ♪ 43 00:02:22,733 --> 00:02:25,600 NARRATOR: Paris. 44 00:02:25,600 --> 00:02:27,800 A city of churches, basilicas, 45 00:02:27,800 --> 00:02:31,966 and almost 2,000 historic monuments. 46 00:02:31,966 --> 00:02:34,600 On April 15, 2019, 47 00:02:34,600 --> 00:02:37,266 the 850-year-old Cathedral 48 00:02:37,266 --> 00:02:39,900 of Notre-Dame de Paris is undergoing 49 00:02:39,900 --> 00:02:42,733 a six-and-a-half-million-dollar renovation 50 00:02:42,733 --> 00:02:45,733 of the spire... 51 00:02:45,733 --> 00:02:51,500 ...when a fire breaks out inside the oak framework of the roof. 52 00:02:51,500 --> 00:02:53,900 After 90 minutes, 53 00:02:53,900 --> 00:02:57,866 the 400-ton timber and lead spire gives way 54 00:02:57,866 --> 00:03:01,266 and crashes through the stone vaulting. 55 00:03:03,600 --> 00:03:06,666 The fire destroys the roof and spire, 56 00:03:06,666 --> 00:03:09,933 and leaves three gaping holes in the vaulting. 57 00:03:09,933 --> 00:03:12,600 The structure is significantly weakened, 58 00:03:12,600 --> 00:03:14,666 and there's an urgent concern. 59 00:03:14,666 --> 00:03:17,133 If the remaining vaulting were to fall, 60 00:03:17,133 --> 00:03:20,766 it could trigger a catastrophic collapse. 61 00:03:20,766 --> 00:03:24,500 PASCAL PRUNET (translated): We didn't know how the vaults, the walls, the buttresses 62 00:03:24,500 --> 00:03:26,400 would behave in the absence of the roof 63 00:03:26,400 --> 00:03:28,133 that had collapsed above. 64 00:03:28,133 --> 00:03:32,133 So, we had to stabilize the structure. 65 00:03:32,133 --> 00:03:34,533 NARRATOR: In the immediate aftermath, 66 00:03:34,533 --> 00:03:36,466 the focus is on protecting 67 00:03:36,466 --> 00:03:39,566 what has survived from further damage. 68 00:03:39,566 --> 00:03:41,466 Engineers race 69 00:03:41,466 --> 00:03:45,000 to install supports beneath Notre-Dame's flying buttresses 70 00:03:45,000 --> 00:03:49,000 to shore up the fragile structure. 71 00:03:49,000 --> 00:03:52,900 Meanwhile, water has saturated the vaults, 72 00:03:52,900 --> 00:03:55,600 adding weight to the weakened stonework, 73 00:03:55,600 --> 00:03:57,966 increasing the chance of a total collapse. 74 00:03:57,966 --> 00:03:59,533 And without the roof, 75 00:03:59,533 --> 00:04:02,966 the building remains open to the elements. 76 00:04:02,966 --> 00:04:07,100 Before they can make the structure watertight, 77 00:04:07,100 --> 00:04:08,900 workers have to remove 78 00:04:08,900 --> 00:04:11,033 40,000 burned and melted scaffolding poles 79 00:04:11,033 --> 00:04:13,366 left over from the spire restoration. 80 00:04:17,100 --> 00:04:20,566 To keep the stonework dry, 81 00:04:20,566 --> 00:04:24,033 the team builds a wooden platform. 82 00:04:24,033 --> 00:04:27,800 On top, a lightweight aluminum frame 83 00:04:27,800 --> 00:04:32,933 covered with water-resistant sheeting 84 00:04:32,933 --> 00:04:35,900 forms a temporary roof 85 00:04:35,900 --> 00:04:38,800 that opens and closes on a system of rollers. 86 00:04:38,800 --> 00:04:43,466 PRUNET (translated): It's an ingenious tool that protects against humidity 87 00:04:43,466 --> 00:04:46,733 and shelters these vaults, so they can dry. 88 00:04:48,600 --> 00:04:51,500 NARRATOR: The rolling roof enables workers to lower 89 00:04:51,500 --> 00:04:53,833 construction materials through the central hole 90 00:04:53,833 --> 00:04:56,366 in the vaulting. 91 00:04:56,366 --> 00:04:58,466 During all this work, 92 00:04:58,466 --> 00:05:01,033 the medieval masterpiece has been closed 93 00:05:01,033 --> 00:05:02,466 to worshippers and tourists alike. 94 00:05:02,466 --> 00:05:05,666 WOMAN: Pretty sad to see it like this. 95 00:05:05,666 --> 00:05:07,500 You can't get close to the building at all. 96 00:05:07,500 --> 00:05:10,500 It's almost like you would walk by it 97 00:05:10,500 --> 00:05:12,233 and not necessarily go to it 98 00:05:12,233 --> 00:05:14,733 as a destination, like it once was. 99 00:05:14,733 --> 00:05:18,433 NARRATOR: And what a destination it was. 100 00:05:18,433 --> 00:05:21,666 Around 13 million people toured Notre-Dame each year 101 00:05:21,666 --> 00:05:24,100 before the fire. 102 00:05:24,100 --> 00:05:25,466 They came to marvel at a building 103 00:05:25,466 --> 00:05:29,466 that pushed the limits of Gothic architecture. 104 00:05:29,466 --> 00:05:32,100 WOMAN: I was very connected to it. 105 00:05:32,100 --> 00:05:35,466 So I was quite broken after, you know, hearing about the fire. 106 00:05:36,700 --> 00:05:39,733 NARRATOR: We still don't know how the fire started. 107 00:05:39,733 --> 00:05:41,200 But three years later, 108 00:05:41,200 --> 00:05:44,266 the ambitious project to restore the cathedral 109 00:05:44,266 --> 00:05:45,633 has ramped up. 110 00:05:45,633 --> 00:05:47,466 MAN (speaking French): 111 00:05:47,466 --> 00:05:50,300 MAN 2 (on radio): 112 00:05:50,300 --> 00:05:51,866   (speaking French) 113 00:05:51,866 --> 00:05:55,800 ♪ ♪ 114 00:05:55,800 --> 00:06:00,566 NARRATOR: The team here has more than tripled in size. 115 00:06:00,566 --> 00:06:03,300 As many as 200 workers are now battling 116 00:06:03,300 --> 00:06:07,666 to bring Notre-Dame back to life. 117 00:06:07,666 --> 00:06:08,766 VILLENEUVE (translated): We all really work 118 00:06:08,766 --> 00:06:11,000 with a lot of love and gratitude, 119 00:06:11,000 --> 00:06:14,300 and we motivate each other to meet the deadline 120 00:06:14,300 --> 00:06:17,766 and reopen the cathedral to the public. 121 00:06:20,600 --> 00:06:22,866 NARRATOR: The French Senate has ruled Notre-Dame 122 00:06:22,866 --> 00:06:26,833 will be rebuilt exactly as it was before the fire. 123 00:06:26,833 --> 00:06:30,933 Donors have contributed almost $900 million 124 00:06:30,933 --> 00:06:32,400 towards this effort. 125 00:06:32,400 --> 00:06:36,233 But the task ahead is enormous. 126 00:06:36,233 --> 00:06:39,800 The team must remove tons of toxic lead dust 127 00:06:39,800 --> 00:06:42,000 that remains of the old lead roof 128 00:06:42,000 --> 00:06:43,833 left over from the fire, 129 00:06:43,833 --> 00:06:49,466 then clean and restore fragile stained-glass windows. 130 00:06:49,466 --> 00:06:52,233 To reconstruct the roof identically, 131 00:06:52,233 --> 00:06:55,666 they must fill the three gaping holes in the stone vaulting, 132 00:06:55,666 --> 00:07:00,433 rebuild the timber framework from almost 1,000 oak beams, 133 00:07:00,433 --> 00:07:05,366 cover it with thousands of square feet of lead tiles, 134 00:07:05,366 --> 00:07:09,766 and raise the iconic 210-foot spire. 135 00:07:11,300 --> 00:07:13,900 It's the largest restoration project 136 00:07:13,900 --> 00:07:16,333 in the cathedral's history. 137 00:07:16,333 --> 00:07:19,533 VILLENEUVE (translated): I only have one goal-- repair and rebuild the cathedral, 138 00:07:19,533 --> 00:07:21,700 put the rooster on top of the spire, 139 00:07:21,700 --> 00:07:22,933 and say, "Mission accomplished." 140 00:07:22,933 --> 00:07:25,133 NARRATOR: That's the plan. 141 00:07:25,133 --> 00:07:29,900 But before they can even start work on this ambitious scheme, 142 00:07:29,900 --> 00:07:33,733 they must shore up the remaining damaged roof. 143 00:07:36,100 --> 00:07:39,033 For hundreds of years, the arched stone vaults, 144 00:07:39,033 --> 00:07:41,500 made from thousands of cubic feet 145 00:07:41,500 --> 00:07:43,733 of interlocking limestone blocks, 146 00:07:43,733 --> 00:07:46,166 supported the roof above. 147 00:07:49,033 --> 00:07:52,533 But now the vaulting is extremely fragile. 148 00:07:52,533 --> 00:07:55,600 Repairing the arches could trigger a collapse. 149 00:07:55,600 --> 00:07:57,800 To stabilize the structure, 150 00:07:57,800 --> 00:08:02,533 the team must install 52 timber support arches 151 00:08:02,533 --> 00:08:06,100 beneath the vaulting so they can rebuild safely. 152 00:08:06,100 --> 00:08:09,100 ♪ ♪ 153 00:08:09,100 --> 00:08:13,000 But installing them more than a hundred feet above the ground 154 00:08:13,000 --> 00:08:15,933 is no small feat. 155 00:08:15,933 --> 00:08:18,366 ♪ ♪ 156 00:08:18,366 --> 00:08:23,333 To do it, scaffolders have built a giant steel structure inside 157 00:08:23,333 --> 00:08:25,400 to allow workers to access 158 00:08:25,400 --> 00:08:28,266 virtually every corner of the immense cathedral. 159 00:08:28,266 --> 00:08:29,833 RÉGIS JAEGER: It's a big job 160 00:08:29,833 --> 00:08:32,333 for our workers because 161 00:08:32,333 --> 00:08:36,966 it's a lot of material and the access is difficult. 162 00:08:38,766 --> 00:08:42,600 We have 1,000 tons of scaffold. 163 00:08:42,600 --> 00:08:45,833 It's a lot of tubes, big and heavy. 164 00:08:45,833 --> 00:08:48,666 It's a big, big challenge. 165 00:08:48,666 --> 00:08:51,300 OWUSU: An extraordinary amount of expertise 166 00:08:51,300 --> 00:08:55,600 has gone into creating a skeleton 167 00:08:55,600 --> 00:08:57,900 to sit inside the building 168 00:08:57,900 --> 00:09:01,800 so that the outer building can be rescued. 169 00:09:01,800 --> 00:09:05,266 NARRATOR: It takes around 20 weeks to build up the scaffolding 170 00:09:05,266 --> 00:09:08,700 inside the cathedral in order to begin 171 00:09:08,700 --> 00:09:10,633 the installation of wooden supports, 172 00:09:10,633 --> 00:09:13,300 shaped to match the geometry of the vaults. 173 00:09:13,300 --> 00:09:15,900 YVES MACEL (translated): This is where you need 174 00:09:15,900 --> 00:09:18,733 to be careful not to hit the scaffolding 175 00:09:18,733 --> 00:09:20,033 or hit the vault. 176 00:09:20,033 --> 00:09:22,866 The challenge is to get everything inside 177 00:09:22,866 --> 00:09:24,533 without damaging anything, 178 00:09:24,533 --> 00:09:26,733 without putting people in danger. 179 00:09:26,733 --> 00:09:29,500 You have to be very, very careful. 180 00:09:29,500 --> 00:09:34,433 NARRATOR: Each temporary support arch is fitted with metal brackets 181 00:09:34,433 --> 00:09:36,433 to secure it in place. 182 00:09:36,433 --> 00:09:40,666 Hydraulic jacks raise it to meet the underside of the vaulting. 183 00:09:40,666 --> 00:09:45,466 MACEL (translated): Each support is unique and has its own specific location. 184 00:09:45,466 --> 00:09:48,433 (drill whirring) 185 00:09:48,433 --> 00:09:52,500 NARRATOR: The arches connect to the rest of the supporting framework. 186 00:09:52,500 --> 00:09:54,166 (translated): If the stones were to move, 187 00:09:54,166 --> 00:09:56,066 they would come to rest on our supports. 188 00:09:56,066 --> 00:09:59,200 Our supports will stay there until the vaults are repaired. 189 00:09:59,200 --> 00:10:00,933 ♪ ♪ 190 00:10:00,933 --> 00:10:04,633 OWUSU: It's almost as if you have to design a building 191 00:10:04,633 --> 00:10:07,500 to keep the building safe. 192 00:10:07,500 --> 00:10:11,900 What you would normally define as a temporary works 193 00:10:11,900 --> 00:10:16,466 has taken a level of ingenuity and a level of skill 194 00:10:16,466 --> 00:10:19,300 which is quite exceptional. 195 00:10:19,300 --> 00:10:26,066 NARRATOR: It takes six months to install all 52 vaulting support arches. 196 00:10:26,066 --> 00:10:28,633 (translated): The structure is no longer at risk of collapsing 197 00:10:28,633 --> 00:10:30,800 after it was weakened by the fire. 198 00:10:30,800 --> 00:10:34,800 NARRATOR: Deputy director of operations Jonathan Truillet 199 00:10:34,800 --> 00:10:36,933 helps coordinate the work to bring Notre-Dame 200 00:10:36,933 --> 00:10:38,766 back from the brink. 201 00:10:38,766 --> 00:10:40,400 ♪ ♪ 202 00:10:40,400 --> 00:10:43,200 TRUILLET (translated): It's a technical and logistical challenge. 203 00:10:43,200 --> 00:10:45,866 And if we don't respect our deadlines, 204 00:10:45,866 --> 00:10:47,900 we'll accumulate delays and never catch up. 205 00:10:47,900 --> 00:10:53,033 NARRATOR: The deadline of 2024 for completion 206 00:10:53,033 --> 00:10:56,266 isn't just a hopeful wish. 207 00:10:56,266 --> 00:10:59,933 This is when all eyes will be on Paris 208 00:10:59,933 --> 00:11:01,433 for the Summer Olympics. 209 00:11:01,433 --> 00:11:05,333 A grand reopening of Notre-Dame 210 00:11:05,333 --> 00:11:08,266 will crown a year of celebrations. 211 00:11:08,266 --> 00:11:09,800 TRUILLET (translated): Everyone must mobilize 212 00:11:09,800 --> 00:11:11,600 to reach this objective. 213 00:11:11,600 --> 00:11:14,500 Even if it is ambitious, it is achievable, 214 00:11:14,500 --> 00:11:17,433 if we have the drive to accomplish it. 215 00:11:17,433 --> 00:11:19,933 ♪ ♪ 216 00:11:19,933 --> 00:11:24,633 NARRATOR: Fewer than three years remain to meet the deadline. 217 00:11:24,633 --> 00:11:26,933 With the vaulting to rebuild, 218 00:11:26,933 --> 00:11:29,200 the roof and spire missing, 219 00:11:29,200 --> 00:11:32,100 and the site still contaminated by lead dust from the fire, 220 00:11:32,100 --> 00:11:35,200 the task is daunting. 221 00:11:35,200 --> 00:11:38,433 TRUILLET (translated): We must work on multiple tasks at the same time, 222 00:11:38,433 --> 00:11:40,866 have several worksites within the worksite. 223 00:11:40,866 --> 00:11:44,066 We must intervene both inside, to clean the site, 224 00:11:44,066 --> 00:11:46,866 and at the same time, above our heads 225 00:11:46,866 --> 00:11:49,866 to rebuild the vaulting and the roof. 226 00:11:50,800 --> 00:11:53,200 NARRATOR: Above the stone vaulting, 227 00:11:53,200 --> 00:11:59,366 Notre-Dame's roof was completely destroyed by the fire. 228 00:11:59,366 --> 00:12:01,400 Now one of the most complex challenges 229 00:12:01,400 --> 00:12:03,933 is to entirely rebuild 230 00:12:03,933 --> 00:12:07,733 the thousand-ton timber and lead roof. 231 00:12:07,733 --> 00:12:13,600 Chief architect Rémi Fromont will oversee the reconstruction 232 00:12:13,600 --> 00:12:18,033 of the medieval roof structure, known as the forest. 233 00:12:18,033 --> 00:12:19,466 FROMONT (translated): We're going to participate 234 00:12:19,466 --> 00:12:22,333 in the reconstruction of this absolutely emblematic, 235 00:12:22,333 --> 00:12:25,066 absolutely unique, absolutely magnificent, 236 00:12:25,066 --> 00:12:27,966 and absolutely iconic work, so it's very exciting. 237 00:12:27,966 --> 00:12:31,566 It was one of the first great Gothic frameworks, 238 00:12:31,566 --> 00:12:32,833 extremely well-designed 239 00:12:32,833 --> 00:12:37,400 and ahead of its time, from a technical point of view. 240 00:12:39,133 --> 00:12:42,400 NARRATOR: During a research project in 2014, 241 00:12:42,400 --> 00:12:44,966 Rémi and his colleague measured the dimensions 242 00:12:44,966 --> 00:12:46,866 of every beam in the forest 243 00:12:46,866 --> 00:12:49,600 to create the first comprehensive survey 244 00:12:49,600 --> 00:12:51,966 of Notre-Dame's roof. 245 00:12:51,966 --> 00:12:54,000 FROMONT (translated): Our surveys were very useful. 246 00:12:54,000 --> 00:12:57,433 It's largely thanks to them that we're able 247 00:12:57,433 --> 00:13:01,333 to restore the roof of the cathedral identically. 248 00:13:02,933 --> 00:13:06,566 NARRATOR: Rémi's team will need 850 oak trees 249 00:13:06,566 --> 00:13:10,100 to reproduce the Gothic roof trusses. 250 00:13:12,266 --> 00:13:18,166 The cathedral's spire will be built from another 1,200 trees. 251 00:13:18,166 --> 00:13:22,966 FROMONT (translated): The spire is a huge task to understand and restore. 252 00:13:22,966 --> 00:13:24,833 It's quite dizzying to think 253 00:13:24,833 --> 00:13:27,966 that we're building a 210-foot-high wooden structure 254 00:13:27,966 --> 00:13:31,400 perched 115 feet above the ground 255 00:13:31,400 --> 00:13:35,066 on 13th-century masonry destroyed by fire. 256 00:13:35,066 --> 00:13:37,433 We're not taking the easy way out, really not. 257 00:13:37,433 --> 00:13:40,133 ♪ ♪ 258 00:13:40,133 --> 00:13:45,366 NARRATOR: The spire was a 400-ton engineering masterpiece. 259 00:13:45,366 --> 00:13:48,400 Hidden beneath the 16 copper statues 260 00:13:48,400 --> 00:13:53,066 and over 100 tons of lead tiles 261 00:13:53,066 --> 00:14:00,166 was a complex skeleton of oak beams, some as long as 65 feet. 262 00:14:00,166 --> 00:14:02,300 The secret of its strength? 263 00:14:02,300 --> 00:14:05,866 A dense lattice of oak tied into the rest of the roof 264 00:14:05,866 --> 00:14:08,133 supports the entire structure. 265 00:14:08,133 --> 00:14:10,200 OWUSU: The spire came to be 266 00:14:10,200 --> 00:14:14,400 the embodiment of the building and of the Paris skyline. 267 00:14:14,400 --> 00:14:17,300 Which took huge imagination and levels 268 00:14:17,300 --> 00:14:20,166 of engineering and creativity and architecture 269 00:14:20,166 --> 00:14:21,833 which is quite, quite exceptional. 270 00:14:21,833 --> 00:14:26,233 NARRATOR: Reconstructing this wooden wonder to match the lost spire 271 00:14:26,233 --> 00:14:28,400 is no simple task. 272 00:14:28,400 --> 00:14:30,600 FROMONT (translated): We'll rebuild identically, 273 00:14:30,600 --> 00:14:33,300 not because it's nice to build in a 13th-century style, 274 00:14:33,300 --> 00:14:36,800 but because we need the new roof to behave just like the old one. 275 00:14:36,800 --> 00:14:38,900 Do it differently 276 00:14:38,900 --> 00:14:41,000 and the structure will behave differently. 277 00:14:41,000 --> 00:14:44,566 The timber that was used originally was green, 278 00:14:44,566 --> 00:14:45,866 that's to say it was not dry. 279 00:14:45,866 --> 00:14:48,166 So we'll use green timber. 280 00:14:49,500 --> 00:14:52,666 NARRATOR: In the 13th century, hewing beams 281 00:14:52,666 --> 00:14:54,500 from hard, seasoned oak 282 00:14:54,500 --> 00:14:57,300 with simple hand tools was arduous work. 283 00:14:59,300 --> 00:15:01,233 So carpenters cut their timber 284 00:15:01,233 --> 00:15:03,633 while it was still soft and green. 285 00:15:03,633 --> 00:15:06,966 But building this way could be risky. 286 00:15:08,833 --> 00:15:12,666 The medieval English town of Chesterfield may bear witness 287 00:15:12,666 --> 00:15:16,066 to the perils of building with green timber. 288 00:15:16,066 --> 00:15:18,333 It's thought the 660-year-old 289 00:15:18,333 --> 00:15:22,300 crooked spire of the parish church could be due to beams 290 00:15:22,300 --> 00:15:25,600 that have warped as they've dried. 291 00:15:25,600 --> 00:15:27,700 For Notre-Dame's spire, 292 00:15:27,700 --> 00:15:31,533 this precarious lean must be avoided at all costs. 293 00:15:31,533 --> 00:15:33,800 FROMONT (translated): We need top-quality timber, 294 00:15:33,800 --> 00:15:36,166 perfectly straight, to avoid this kind of problem. 295 00:15:36,166 --> 00:15:38,366 Working with green wood requires 296 00:15:38,366 --> 00:15:41,700 an extremely rigorous choice of tree. 297 00:15:41,700 --> 00:15:45,600 NARRATOR: In public and private forests across France, 298 00:15:45,600 --> 00:15:49,700 the hunt for 2,000 perfect oaks for Notre-Dame's roof 299 00:15:49,700 --> 00:15:52,966 and spire begins. 300 00:15:52,966 --> 00:15:54,133 One third of the country, 301 00:15:54,133 --> 00:15:58,466 65,000 square miles, is covered by forests. 302 00:15:58,466 --> 00:16:01,333 (translated): We're going to choose the trees. 303 00:16:01,333 --> 00:16:03,166 NARRATOR: This crew of forestiers 304 00:16:03,166 --> 00:16:05,966 has their work cut out for them. 305 00:16:05,966 --> 00:16:10,366 They must source 60 flawless oaks for the spire 306 00:16:10,366 --> 00:16:12,600 from an 8,000-acre forest. 307 00:16:12,600 --> 00:16:14,266 (translated): We must inspect the tree from all angles, 308 00:16:14,266 --> 00:16:16,633 otherwise you'll never know if there is a defect. 309 00:16:17,833 --> 00:16:20,700 NARRATOR: The oaks felled for Notre-Dame 310 00:16:20,700 --> 00:16:23,433 form part of France's annual forest management quota. 311 00:16:23,433 --> 00:16:25,300 LOÏC EON (translated): That way. 312 00:16:25,300 --> 00:16:27,600 But now we need to get a bit closer, 313 00:16:27,600 --> 00:16:29,733 because something is not quite right. 314 00:16:29,733 --> 00:16:32,666 There's damage 20 feet up, so we can't choose this one. 315 00:16:32,666 --> 00:16:36,166 It won't meet the specifications given for Notre-Dame's spire. 316 00:16:36,166 --> 00:16:40,433 So, we need to look for another tree. 317 00:16:40,433 --> 00:16:42,366 MAN (speaking French): 318 00:16:42,366 --> 00:16:46,066 NARRATOR: This oak was damaged as it grew. 319 00:16:46,066 --> 00:16:49,533 These twisted fibers make it too weak for Notre-Dame's spire. 320 00:16:50,600 --> 00:16:53,300 But on the other side of the clearing, 321 00:16:53,300 --> 00:16:54,733 another candidate emerges. 322 00:16:54,733 --> 00:16:56,666 EON (translated): No damage, 323 00:16:56,666 --> 00:16:59,300 but we need to check the diameter. 324 00:17:01,400 --> 00:17:03,466 We have a tree two feet in diameter. 325 00:17:03,466 --> 00:17:07,400 AHMET CIRPAN (translated): In terms of felling it, there's no problem. 326 00:17:07,400 --> 00:17:11,133 (revving) 327 00:17:11,133 --> 00:17:13,466 NARRATOR: Logger Ahmet Cirpan begins by making 328 00:17:13,466 --> 00:17:15,466 a cut that will direct the tree 329 00:17:15,466 --> 00:17:18,400 to fall into the clearing. 330 00:17:20,500 --> 00:17:26,466 (translated): It will go between those two trees, here, in this direction. 331 00:17:26,466 --> 00:17:29,666 I don't cut with my chainsaw at random. 332 00:17:30,966 --> 00:17:35,466 Okay, now we can start the final cut. 333 00:17:38,033 --> 00:17:40,766 (saw buzzing) 334 00:17:43,466 --> 00:17:46,700 ♪ ♪ 335 00:17:52,300 --> 00:17:55,966 Yes, that's why we can't have anyone getting in the way. 336 00:17:58,133 --> 00:18:00,533 NARRATOR: Notre-Dame's medieval carpenters used markings 337 00:18:00,533 --> 00:18:04,366 to help them reassemble the beams correctly up on the roof. 338 00:18:04,366 --> 00:18:08,133 ♪ ♪ 339 00:18:08,133 --> 00:18:10,233 Today, this team attaches a barcode 340 00:18:10,233 --> 00:18:12,500 to each oak destined for the cathedral, 341 00:18:12,500 --> 00:18:16,933 so they can track it from the forest to its final position 342 00:18:16,933 --> 00:18:20,266 in the new spire. 343 00:18:20,266 --> 00:18:21,366 It takes several months 344 00:18:21,366 --> 00:18:24,766 to complete the painstaking search to source 345 00:18:24,766 --> 00:18:28,466 and fell their target of 60 trees. 346 00:18:28,466 --> 00:18:32,000 FROMONT (translated): We're going to restore and rebuild the missing parts, 347 00:18:32,000 --> 00:18:36,000 and that's something unique in a career. 348 00:18:36,000 --> 00:18:38,533 We'll do it with all our heart, passion, 349 00:18:38,533 --> 00:18:39,900 and above all, know-how. 350 00:18:47,500 --> 00:18:50,966 NARRATOR: Oak will form the backbone of the spire, 351 00:18:50,966 --> 00:18:56,500 but it will be wrapped in a heavy metal-- lead. 352 00:18:56,500 --> 00:19:00,000 Although the spire was almost completely incinerated, 353 00:19:00,000 --> 00:19:02,366 its pinnacle survived the inferno. 354 00:19:02,366 --> 00:19:07,666 Lodged in the vaulting stone, 355 00:19:07,666 --> 00:19:09,433 the team gently nudges it free... 356 00:19:09,433 --> 00:19:11,900 WORKERS (speaking French): 357 00:19:11,900 --> 00:19:14,033 NARRATOR: ...and carefully winches it down. 358 00:19:14,033 --> 00:19:17,133 L'HÉRITIER: We can still see the structure 359 00:19:17,133 --> 00:19:20,500 of the spire was made, 360 00:19:20,500 --> 00:19:25,333 with this fine lead sheets of a few millimeters thick 361 00:19:25,333 --> 00:19:27,200 that were used 362 00:19:27,200 --> 00:19:31,333 on the entire structure of the spire. 363 00:19:31,333 --> 00:19:34,300 NARRATOR: They find six decorative lead roses 364 00:19:34,300 --> 00:19:37,233 attached to the spire section. 365 00:19:37,233 --> 00:19:40,600 We will be able to study how this decoration was made. 366 00:19:40,600 --> 00:19:43,266 Touching the spire 367 00:19:43,266 --> 00:19:48,133 that was just taken down from the vaults today, 368 00:19:48,133 --> 00:19:50,266 it's a magical moment. 369 00:19:50,266 --> 00:19:55,300 NARRATOR: And there are more surprises to come. 370 00:19:55,300 --> 00:19:57,333 Lead was decorative and kept the cathedral watertight. 371 00:19:57,333 --> 00:20:00,966 But there's another metal used here 372 00:20:00,966 --> 00:20:02,766 that allowed Notre-Dame's masons 373 00:20:02,766 --> 00:20:04,633 to push the limits of Gothic stonework. 374 00:20:04,633 --> 00:20:06,933 ♪ ♪ 375 00:20:06,933 --> 00:20:10,233 Innovations such as flying buttresses 376 00:20:10,233 --> 00:20:12,866 to hold up the thin outer walls 377 00:20:12,866 --> 00:20:14,700 allowed medieval masons to build 378 00:20:14,700 --> 00:20:20,400 incredibly high, without needing massively thick walls. 379 00:20:23,466 --> 00:20:26,300 As the team examines the structure closely, 380 00:20:26,300 --> 00:20:29,433 they discover metal throughout the cathedral 381 00:20:29,433 --> 00:20:32,966 that could unlock more of its architectural mysteries, 382 00:20:32,966 --> 00:20:37,633 from the nails that join timber beams 383 00:20:37,633 --> 00:20:39,133 to iron bars that brace 384 00:20:39,133 --> 00:20:43,233 and hold secure the stunning medieval stained glass. 385 00:20:45,533 --> 00:20:48,866 L'HÉRITIER: I was amazed that there's so many iron in, in this building 386 00:20:48,866 --> 00:20:54,066 that was never truly studied before. 387 00:20:54,066 --> 00:20:56,866 The staples that we see here, 388 00:20:56,866 --> 00:20:59,866 they're embedded in the, 389 00:20:59,866 --> 00:21:02,800 maybe the oldest part of Notre-Dame's masonry. 390 00:21:02,800 --> 00:21:07,566 NARRATOR: These 18-inch-long iron "staples" 391 00:21:07,566 --> 00:21:09,700 secure the great arches beneath 392 00:21:09,700 --> 00:21:11,633 and prevent the stone blocks from collapsing 393 00:21:11,633 --> 00:21:15,133 under the enormous weight. 394 00:21:15,133 --> 00:21:20,000 65 feet above, along the very top of Notre-Dame's walls, 395 00:21:20,000 --> 00:21:22,000 the destruction of the roof 396 00:21:22,000 --> 00:21:24,933 has revealed previously concealed ironwork 397 00:21:24,933 --> 00:21:27,333 that may have made the structure's height 398 00:21:27,333 --> 00:21:29,800 and slender form possible. 399 00:21:29,800 --> 00:21:31,833 It's really exciting, because 400 00:21:31,833 --> 00:21:34,700 we're dealing with unknown structures 401 00:21:34,700 --> 00:21:36,466 on the top of the walls 402 00:21:36,466 --> 00:21:40,166 that are so far unique in Gothic architecture. 403 00:21:40,166 --> 00:21:44,366 NARRATOR: Medieval builders may have worried 404 00:21:44,366 --> 00:21:47,566 that the top of Notre-Dame's tall, slender walls 405 00:21:47,566 --> 00:21:50,300 could be an Achilles' heel. 406 00:21:50,300 --> 00:21:54,233 The weight of the roof could push the stones apart. 407 00:21:54,233 --> 00:21:56,700 The destruction of the roof has revealed 408 00:21:56,700 --> 00:21:58,900 the builders joined these stones together 409 00:21:58,900 --> 00:22:01,833 with more than 500 staples, 410 00:22:01,833 --> 00:22:07,466 creating a ring of iron holding the walls together. 411 00:22:07,466 --> 00:22:11,133 This engineering masterstroke has remained hidden 412 00:22:11,133 --> 00:22:13,800 under the roof of Notre-Dame for hundreds of years. 413 00:22:15,466 --> 00:22:16,700 L'HÉRITIER: The staples, 414 00:22:16,700 --> 00:22:20,666 with the flying buttresses, are two ways 415 00:22:20,666 --> 00:22:23,966 of preventing the stones to, to collapse. 416 00:22:23,966 --> 00:22:27,866 It's an ancient form, a form which is known since antiquity. 417 00:22:27,866 --> 00:22:29,600 ♪ ♪ 418 00:22:29,600 --> 00:22:32,033 NARRATOR: Ancient engineers used iron staples 419 00:22:32,033 --> 00:22:35,333 to lock the stones of giant megastructures into place. 420 00:22:36,900 --> 00:22:39,533 These holes in the walls of Rome's Colosseum 421 00:22:39,533 --> 00:22:41,966 were once filled with iron staples 422 00:22:41,966 --> 00:22:43,733 that pinned the structure together. 423 00:22:43,733 --> 00:22:45,900 But in medieval Paris, 424 00:22:45,900 --> 00:22:50,266 masons used this technology to revolutionize architecture. 425 00:22:50,266 --> 00:22:52,166 L'HÉRITIER: It looks like, 426 00:22:52,166 --> 00:22:56,633 in Notre-Dame, we're trying to use ancient forms 427 00:22:56,633 --> 00:22:59,066 of reinforcement, such as the staple, 428 00:22:59,066 --> 00:23:02,433 in order to build a new form of architecture; 429 00:23:02,433 --> 00:23:06,700 really high, really thin Gothic structures, 430 00:23:06,700 --> 00:23:09,533 of which Notre-Dame is kind of the first true example. 431 00:23:09,533 --> 00:23:11,733 ♪ ♪ 432 00:23:11,733 --> 00:23:14,366 NARRATOR: At his lab, Maxime unlocks the secrets 433 00:23:14,366 --> 00:23:16,500 of each individual iron staple. 434 00:23:18,066 --> 00:23:20,000 L'HÉRITIER: Like, we're acting 435 00:23:20,000 --> 00:23:21,700 as some kind of detectives, 436 00:23:21,700 --> 00:23:24,133 trying to find out the digital prints, 437 00:23:24,133 --> 00:23:25,366 the digital signature, 438 00:23:25,366 --> 00:23:28,133 of each of these staples 439 00:23:28,133 --> 00:23:30,133 and to try to rebuild 440 00:23:30,133 --> 00:23:34,000 their path from the workshop to the building site. 441 00:23:35,666 --> 00:23:38,200 NARRATOR: Radiocarbon dating of organic material 442 00:23:38,200 --> 00:23:39,500 left over from the smelting process 443 00:23:39,500 --> 00:23:42,600 confirms the staples were installed 444 00:23:42,600 --> 00:23:44,800 in the early 13th century, 445 00:23:44,800 --> 00:23:48,200 when this part of the cathedral was built. 446 00:23:50,333 --> 00:23:54,566 These are the oldest pieces of iron used in a Gothic church 447 00:23:54,566 --> 00:23:56,733 that we know of so far. 448 00:23:56,733 --> 00:23:59,200 That's a huge discovery. 449 00:23:59,200 --> 00:24:01,733 This is revolution in Gothic architecture. 450 00:24:01,733 --> 00:24:04,833 No other Gothic monument had used iron 451 00:24:04,833 --> 00:24:07,433 in such a way before Notre-Dame. 452 00:24:09,633 --> 00:24:13,533 NARRATOR: Maxime examines the microstructure of the iron. 453 00:24:13,533 --> 00:24:16,066 Each staple was produced 454 00:24:16,066 --> 00:24:17,800 by welding together multiple pieces, 455 00:24:17,800 --> 00:24:20,766 suggesting that this iron was recycled. 456 00:24:20,766 --> 00:24:24,933 L'HÉRITIER: The weld is the result of the mixing of scrap iron 457 00:24:24,933 --> 00:24:27,466 to make a brand-new iron staple. 458 00:24:27,466 --> 00:24:31,766 We're maybe dealing with the richest building site 459 00:24:31,766 --> 00:24:32,900 at that time, 460 00:24:32,900 --> 00:24:36,033 and knowing that it might have used 461 00:24:36,033 --> 00:24:39,366 almost 90% recycled iron 462 00:24:39,366 --> 00:24:42,400 opens new perspective. 463 00:24:42,400 --> 00:24:45,133 NARRATOR: The research shows recycling iron 464 00:24:45,133 --> 00:24:49,000 may have been common on the building site of Notre-Dame, 465 00:24:49,000 --> 00:24:52,466 shedding new light on medieval building practices. 466 00:24:54,033 --> 00:24:56,666 The lab's electron microscope reveals further clues 467 00:24:56,666 --> 00:25:00,266 to the lengths that Notre-Dame's builders went to 468 00:25:00,266 --> 00:25:03,833 in sourcing the material. 469 00:25:03,833 --> 00:25:05,666 L'HÉRITIER: What we discovered is that 470 00:25:05,666 --> 00:25:09,333 every single staple has a different chemical signature. 471 00:25:09,333 --> 00:25:13,300 All these staples, they come from different iron 472 00:25:13,300 --> 00:25:15,333 that was made in different places. 473 00:25:15,333 --> 00:25:21,233 It means that there's a truly active iron market in Paris, 474 00:25:21,233 --> 00:25:25,200 gathering iron from many, many different origins. 475 00:25:26,733 --> 00:25:30,700 NARRATOR: These hidden iron staples may have also played a critical role 476 00:25:30,700 --> 00:25:33,700 in saving the building in the wake of the fire. 477 00:25:33,700 --> 00:25:38,966 The staples were placed by the medieval master mason 478 00:25:38,966 --> 00:25:42,200 to reinforce the upper main walls. 479 00:25:42,200 --> 00:25:44,733 They might have helped the walls 480 00:25:44,733 --> 00:25:46,933 to prevent collapsing during the fire. 481 00:25:46,933 --> 00:25:50,666 OWUSU: As a conservationist, 482 00:25:50,666 --> 00:25:53,833 it's teaching us how expert 483 00:25:53,833 --> 00:25:57,566 these builders were in those days. 484 00:25:57,566 --> 00:25:58,733 It's a testament 485 00:25:58,733 --> 00:26:02,933 to their technical competence and their vision 486 00:26:02,933 --> 00:26:06,200 that they put in these structural elements 487 00:26:06,200 --> 00:26:09,166 which have preserved the building for us. 488 00:26:13,100 --> 00:26:15,600 NARRATOR: But Notre-Dame's marvels 489 00:26:15,600 --> 00:26:17,900 go beyond the walls and roof. 490 00:26:17,900 --> 00:26:20,066 The great cathedral's medieval builders 491 00:26:20,066 --> 00:26:24,733 also pushed the limits of what could be made with glass. 492 00:26:25,866 --> 00:26:30,066 The three rose windows date from the 13th century, 493 00:26:30,066 --> 00:26:36,233 and together, they're made up of over 1,100 panels. 494 00:26:36,233 --> 00:26:39,066 Protected by the stone vaulting, 495 00:26:39,066 --> 00:26:41,733 they survived the fire unscathed. 496 00:26:41,733 --> 00:26:44,900 ♪ ♪ 497 00:26:44,900 --> 00:26:47,100 These kaleidoscopic wonders are filled 498 00:26:47,100 --> 00:26:51,133 with depictions of biblical scenes and saints. 499 00:26:58,933 --> 00:27:01,800 The scaffolding gives access to these rose windows 500 00:27:01,800 --> 00:27:04,700 so experts can decode their secrets. 501 00:27:04,700 --> 00:27:07,633 BOULANGER: It is a very unique opportunity, 502 00:27:07,633 --> 00:27:12,666 because we won't see them again in the same way, never. 503 00:27:13,400 --> 00:27:16,433 (in French): 504 00:27:16,433 --> 00:27:19,500 CLAUDINE LOISEL: 505 00:27:19,500 --> 00:27:22,166 NARRATOR: Glass scientist Claudine Loisel 506 00:27:22,166 --> 00:27:26,033 and historians Karine Boulanger and Elisabeth Pillet 507 00:27:26,033 --> 00:27:29,433 are working on the largest window in Notre-Dame. 508 00:27:29,433 --> 00:27:31,833 The gigantic south rose window 509 00:27:31,833 --> 00:27:35,866 measures almost 42 feet in diameter. 510 00:27:35,866 --> 00:27:39,233 They're busy mapping every shard of glass. 511 00:27:40,266 --> 00:27:42,300 PILLET (translated): It's a really big job. 512 00:27:42,300 --> 00:27:45,033 In fact, I think at the beginning, 513 00:27:45,033 --> 00:27:47,066 when we looked at this rose window, we had no idea 514 00:27:47,066 --> 00:27:49,233 of all the questions it would raise. 515 00:27:49,233 --> 00:27:52,866 NARRATOR: They hope to build a complete picture 516 00:27:52,866 --> 00:27:56,433 of how the window has evolved over centuries of restoration. 517 00:27:56,433 --> 00:28:00,300 The team must first identify what is original 518 00:28:00,300 --> 00:28:03,300 13th-century glass and what is glass 519 00:28:03,300 --> 00:28:06,166 from subsequent restorations. 520 00:28:06,166 --> 00:28:09,100 BOULANGER (in French): 521 00:28:09,100 --> 00:28:11,366 (in English): You see, there is a difference 522 00:28:11,366 --> 00:28:14,033 between this yellow and this one. 523 00:28:14,033 --> 00:28:15,333 This one is more translucent. 524 00:28:15,333 --> 00:28:17,800 It's 19th-century glass. 525 00:28:17,800 --> 00:28:20,233 This one is 13th-century glass. 526 00:28:20,233 --> 00:28:22,933 The difference in colors results from 527 00:28:22,933 --> 00:28:26,833 the composition of the glass, which was different 528 00:28:26,833 --> 00:28:30,000 between the medieval time and 19th century. 529 00:28:30,000 --> 00:28:34,000 NARRATOR: But there's a problem baked 530 00:28:34,000 --> 00:28:36,333 into the original medieval glass: 531 00:28:36,333 --> 00:28:37,833 it's slowly decaying. 532 00:28:37,833 --> 00:28:39,000 LOISEL: On the older glass, 533 00:28:39,000 --> 00:28:41,666 you observe much more corrosion process 534 00:28:41,666 --> 00:28:44,933 in the glass composition. 535 00:28:44,933 --> 00:28:48,400 This glass composition was more sensitive to the environment. 536 00:28:48,400 --> 00:28:51,466 NARRATOR: In the 13th century, 537 00:28:51,466 --> 00:28:54,666 glassmakers used potash. 538 00:28:54,666 --> 00:28:58,933 Made from burnt wood and ferns rich in potassium, 539 00:28:58,933 --> 00:29:02,166 potash reduced the melting point of the ingredients 540 00:29:02,166 --> 00:29:03,866 used to make glass. 541 00:29:03,866 --> 00:29:08,500 By the 19th century, sodium carbonate combined with 542 00:29:08,500 --> 00:29:12,900 calcium oxide was used instead, and produced more stable glass 543 00:29:12,900 --> 00:29:15,800 that did not corrode. 544 00:29:20,066 --> 00:29:23,100 This factory on the banks of the Loire River in France 545 00:29:23,100 --> 00:29:26,033 is one of the last places in the world that can produce 546 00:29:26,033 --> 00:29:29,466 stained glass using medieval mouth-blowing techniques. 547 00:29:29,466 --> 00:29:33,533 SIMON BALLAGH: We produce glass for major historical buildings 548 00:29:33,533 --> 00:29:36,933 as Versailles or the White House. 549 00:29:38,633 --> 00:29:41,400 NARRATOR: The team starts by mixing sand, 550 00:29:41,400 --> 00:29:44,533 metal oxide for color, 551 00:29:44,533 --> 00:29:48,000 sodium carbonate, and calcium. 552 00:29:49,300 --> 00:29:53,166 They heat the mixture to over 2,000 degrees Fahrenheit 553 00:29:53,166 --> 00:29:55,700 and build up layers of the molten glass 554 00:29:55,700 --> 00:29:58,766 on the end of a blowpipe. 555 00:29:58,766 --> 00:30:03,100 The glassblower forms a sphere from the red-hot mass, 556 00:30:03,100 --> 00:30:05,166 rolling it to maintain this shape, 557 00:30:05,166 --> 00:30:09,633 which is critical to form an even thickness of glass. 558 00:30:09,633 --> 00:30:12,300 It's manual know-how. 559 00:30:12,300 --> 00:30:15,233 There is absolutely no machines, 560 00:30:15,233 --> 00:30:17,933 and the glassblowers uses their sense, their feeling, 561 00:30:17,933 --> 00:30:20,600 to blow one glass sheet. 562 00:30:22,066 --> 00:30:24,200 HERVÉ GRIMAL (translated): Glass is a living material. 563 00:30:24,200 --> 00:30:25,433 It takes a long time 564 00:30:25,433 --> 00:30:27,733 to get to know it, to feel the material 565 00:30:27,733 --> 00:30:29,433 at your fingertips. 566 00:30:29,433 --> 00:30:34,033 NARRATOR: The glassblowers enlist the help of gravity. 567 00:30:34,033 --> 00:30:38,200 They swing the 15-pound ball of glass in a 13-foot-deep pit 568 00:30:38,200 --> 00:30:42,533 to elongate the ball into a tube. 569 00:30:42,533 --> 00:30:43,733 GRIMAL (translated): It's a profession 570 00:30:43,733 --> 00:30:46,433 where there's weight and there's heat. 571 00:30:46,433 --> 00:30:49,466 So you have to be strong, tough at times. 572 00:30:49,466 --> 00:30:51,600 It's a very demanding job. 573 00:30:51,600 --> 00:30:54,333 ♪ ♪ 574 00:30:54,333 --> 00:30:58,966 NARRATOR: Hervé has blown glass here for more than 33 years. 575 00:30:58,966 --> 00:31:01,500 GRIMAL (translated): For us, it's about always having the right length, 576 00:31:01,500 --> 00:31:02,933 the right diameter, 577 00:31:02,933 --> 00:31:06,900 and the right thickness of the glass, too. 578 00:31:08,366 --> 00:31:11,966 NARRATOR: Once the cylinder has cooled, they make a single cut... 579 00:31:15,400 --> 00:31:19,000 ...and send it to a special furnace, where it's unrolled. 580 00:31:19,000 --> 00:31:24,300 Extreme heat of nearly 1,400 degrees Fahrenheit 581 00:31:24,300 --> 00:31:28,133 and a wood block smooth out the glass 582 00:31:28,133 --> 00:31:31,300 and minimize imperfections. 583 00:31:31,300 --> 00:31:35,933 GRIMAL (translated): The goal is to try to get a very even thickness, 584 00:31:35,933 --> 00:31:39,033 to achieve the perfect sheet. 585 00:31:41,700 --> 00:31:47,333 NARRATOR: They carefully inspect each pane and remove any rough edges. 586 00:31:47,333 --> 00:31:50,066 BALLAGH: Every glass sheet is different, and it has the spirit 587 00:31:50,066 --> 00:31:52,566 of the glassblower. 588 00:31:52,566 --> 00:31:54,766 Losing this patrimoine and know-how would be a disaster. 589 00:31:54,766 --> 00:31:57,733 ♪ ♪ 590 00:31:57,733 --> 00:31:59,366 NARRATOR: The factory marries these techniques 591 00:31:59,366 --> 00:32:01,000 with the latest technology 592 00:32:01,000 --> 00:32:03,500 to accurately reproduce stained glass. 593 00:32:03,500 --> 00:32:07,433 BALLAGH: We can fit perfectly 594 00:32:07,433 --> 00:32:10,500 with the old colors by using 595 00:32:10,500 --> 00:32:16,800 tools like spectrophotometry, like X-rays. 596 00:32:16,800 --> 00:32:19,500 And this allows us to know exactly what are the elements 597 00:32:19,500 --> 00:32:24,666 that are in the glass and reproduce it for the future. 598 00:32:24,666 --> 00:32:27,433 GRIMAL (translated): We'll be making glass 599 00:32:27,433 --> 00:32:30,433 for the restoration of Notre-Dame in Paris, 600 00:32:30,433 --> 00:32:34,200 which will be a high point in my career. 601 00:32:34,200 --> 00:32:37,066 Well, it will make for a nice resumé! 602 00:32:37,066 --> 00:32:39,933 NARRATOR: The team's knowledge of historic techniques, 603 00:32:39,933 --> 00:32:45,533 combined with modern technology, enables them to reproduce 604 00:32:45,533 --> 00:32:49,733 any of Notre-Dame's stained glass from any century. 605 00:32:52,900 --> 00:32:54,133 BOULANGER: A stained-glass window 606 00:32:54,133 --> 00:32:57,066 is always a mixture of original glass 607 00:32:57,066 --> 00:33:01,633 and restoration from every century, almost. 608 00:33:01,633 --> 00:33:04,433 Until the 20th century, 609 00:33:04,433 --> 00:33:06,733 when a glass was too badly damaged, 610 00:33:06,733 --> 00:33:08,366 we had to replace it. 611 00:33:08,366 --> 00:33:12,466 NARRATOR: While mapping the south rose window, 612 00:33:12,466 --> 00:33:15,133 they uncover an unusual trend. 613 00:33:15,133 --> 00:33:18,900 They expect to see glass from multiple restorations 614 00:33:18,900 --> 00:33:21,066 spanning eight centuries. 615 00:33:22,900 --> 00:33:26,933 But they're finding original 13th-century glass, 616 00:33:26,933 --> 00:33:31,300 glass installed during the 19th century, 617 00:33:31,300 --> 00:33:34,800 with some panels containing both. 618 00:33:34,800 --> 00:33:37,433 BOULANGER: We are finding lots of things. 619 00:33:37,433 --> 00:33:38,800 They altered quite strongly 620 00:33:38,800 --> 00:33:41,466 the design of the panels. 621 00:33:41,466 --> 00:33:44,266 NARRATOR: While the glass team 622 00:33:44,266 --> 00:33:46,900 has this unprecedented access, they must work fast 623 00:33:46,900 --> 00:33:50,200 to solve the mystery of why the south rose window 624 00:33:50,200 --> 00:33:54,966 only has 13th- and 19th-century glass. 625 00:33:54,966 --> 00:33:58,133 ♪ ♪ 626 00:33:58,133 --> 00:34:02,666 The clock is ticking for the architects and restorers. 627 00:34:02,666 --> 00:34:06,933 To meet the challenge of reopening Notre-Dame in 2024, 628 00:34:06,933 --> 00:34:10,133 the workforce here has increased dramatically. 629 00:34:10,133 --> 00:34:13,666 Up to 200 people pass through the site each day. 630 00:34:13,666 --> 00:34:16,933 ♪ ♪ 631 00:34:16,933 --> 00:34:18,066 But the lead dust 632 00:34:18,066 --> 00:34:21,300 that coats every surface makes operating here 633 00:34:21,300 --> 00:34:22,800 potentially dangerous. 634 00:34:22,800 --> 00:34:26,700 Protective clothing is essential. 635 00:34:26,700 --> 00:34:29,866 Blaise Gomis is part of a team dedicated 636 00:34:29,866 --> 00:34:32,700 to safeguarding workers from the deadly effects 637 00:34:32,700 --> 00:34:34,166 of lead poisoning. 638 00:34:34,166 --> 00:34:39,133 Without them, this huge operation would grind to a halt. 639 00:34:39,133 --> 00:34:41,433 GOMIS (translated): Between the polluted zone and the clean zone, 640 00:34:41,433 --> 00:34:43,233 there's us. 641 00:34:43,233 --> 00:34:45,000 You have to go through us. 642 00:34:45,000 --> 00:34:47,200 We take names so we have a count of the people on site. 643 00:34:47,200 --> 00:34:49,333 Then, after they finish their job, 644 00:34:49,333 --> 00:34:52,500 when they leave, they must go past me again. 645 00:34:53,866 --> 00:34:55,400 (in French): 646 00:34:56,933 --> 00:34:58,666 WOMAN: 647 00:34:58,666 --> 00:34:59,833 GOMIS: 648 00:34:59,833 --> 00:35:01,033 WOMAN: 649 00:35:02,933 --> 00:35:05,033 GOMIS (translated): Lead, as you know, is harmful. 650 00:35:05,033 --> 00:35:06,666 So they must be equipped. 651 00:35:06,666 --> 00:35:08,033 We give them overalls, 652 00:35:08,033 --> 00:35:11,400 underwear, boots, and helmets. 653 00:35:11,400 --> 00:35:12,766 (suit zipping) 654 00:35:14,600 --> 00:35:16,266 ♪ ♪ 655 00:35:16,266 --> 00:35:18,566 And when they leave, they take showers to make sure 656 00:35:18,566 --> 00:35:21,033 they eliminate as much lead as possible. 657 00:35:25,166 --> 00:35:28,700 NARRATOR: To make the site safe, the team's next challenge 658 00:35:28,700 --> 00:35:30,733 is to remove all the toxic lead dust. 659 00:35:30,733 --> 00:35:35,300 They tackle the cleaning zone by zone, 660 00:35:35,300 --> 00:35:38,833 eventually decontaminating the entire cathedral. 661 00:35:38,833 --> 00:35:42,966 But this operation kicks dust into the air. 662 00:35:42,966 --> 00:35:45,033 (vacuum whirring) 663 00:35:45,033 --> 00:35:46,533 Workers in an area being cleaned 664 00:35:46,533 --> 00:35:49,433 must wear heavy-duty breathing equipment. 665 00:35:52,133 --> 00:35:55,300 Clara Dupuydauby 666 00:35:55,300 --> 00:35:58,700 is one of 40 decontamination experts 667 00:35:58,700 --> 00:36:01,766 that use special vacuums to meticulously clean every inch 668 00:36:01,766 --> 00:36:05,100 of Notre-Dame's vaulting, walls, 669 00:36:05,100 --> 00:36:09,200 pillars, and floors. 670 00:36:09,200 --> 00:36:10,366 With this equipment, 671 00:36:10,366 --> 00:36:12,933 we only work two hours and a half 672 00:36:12,933 --> 00:36:15,800 at a time, and we need to stop to take a break. 673 00:36:15,800 --> 00:36:17,233 We go have lunch. 674 00:36:17,233 --> 00:36:19,533 And two hours and a half, and we go home. 675 00:36:19,533 --> 00:36:24,400 NARRATOR: Vacuuming the lead dust will take eight months. 676 00:36:24,400 --> 00:36:27,633 Then restorers can move on to deep-clean the stone 677 00:36:27,633 --> 00:36:31,366 for the first time in its history. 678 00:36:31,366 --> 00:36:32,600 Inside Notre-Dame, 679 00:36:32,600 --> 00:36:35,200 it's already possible to get a sense of how 680 00:36:35,200 --> 00:36:37,133 dramatically changed the cathedral will be 681 00:36:37,133 --> 00:36:41,566 after the cleaning. 682 00:36:41,566 --> 00:36:43,500 Beneath the lead and centuries of smoke 683 00:36:43,500 --> 00:36:48,033 from millions of candles lies gleaming limestone. 684 00:36:48,033 --> 00:36:52,233 This is how the cathedral looked 850 years ago 685 00:36:52,233 --> 00:36:53,366 and will again soon. 686 00:36:53,366 --> 00:36:56,333 VILLENEUVE (translated): Here are the stages. 687 00:36:56,333 --> 00:36:57,766 PRUNET (translated): First step, second step... 688 00:36:57,766 --> 00:36:59,766 Dirty, intermediate, and final. 689 00:36:59,766 --> 00:37:01,500 That's great. 690 00:37:01,500 --> 00:37:04,200 (drill whirring) 691 00:37:04,200 --> 00:37:06,100 NARRATOR: The restorers working at Notre-Dame 692 00:37:06,100 --> 00:37:10,100 are among France's foremost experts in their fields. 693 00:37:10,100 --> 00:37:12,233 ♪ ♪ 694 00:37:12,233 --> 00:37:14,200 Guiding this impressive concentration 695 00:37:14,200 --> 00:37:15,933 of medieval knowledge 696 00:37:15,933 --> 00:37:18,266 are chief architects Pascal Prunet 697 00:37:18,266 --> 00:37:21,266 and Philippe Villeneuve. 698 00:37:21,266 --> 00:37:24,400 VILLENEUVE (speaking French): 699 00:37:24,400 --> 00:37:27,800 (translated): Let's go and meet the cleaning team. 700 00:37:27,800 --> 00:37:28,933 (translated): The stone's changing color. 701 00:37:28,933 --> 00:37:30,200 We're very satisfied with that. 702 00:37:30,200 --> 00:37:33,766 But we know this is only the first stage of the cleaning. 703 00:37:33,766 --> 00:37:36,433 (translated): But after, we'll be able to work without masks, 704 00:37:36,433 --> 00:37:37,533 so that's the goal. 705 00:37:40,833 --> 00:37:43,166 VILLENEUVE (translated): When we look at this vaulting, it's clear to us 706 00:37:43,166 --> 00:37:45,000 that this cathedral 707 00:37:45,000 --> 00:37:46,200 will be extraordinary. 708 00:37:46,200 --> 00:37:48,400 So it's all enormously energizing. 709 00:37:49,700 --> 00:37:52,200 NARRATOR: But this team still has a big job ahead 710 00:37:52,200 --> 00:37:55,766 if they want to reopen the cathedral in 2024. 711 00:37:57,433 --> 00:38:00,033 VILLENEUVE (translated): It's a completely crazy deadline. 712 00:38:00,033 --> 00:38:03,300 But despite everything, we continue to work 713 00:38:03,300 --> 00:38:05,333 so it can be met. 714 00:38:05,333 --> 00:38:07,333 ♪ ♪ 715 00:38:07,333 --> 00:38:08,566 NARRATOR: To meet the deadline, 716 00:38:08,566 --> 00:38:12,766 the team cannot afford any unexpected delays. 717 00:38:12,766 --> 00:38:15,566 But an insidious threat to Notre-Dame's stonework 718 00:38:15,566 --> 00:38:17,733 is developing. 719 00:38:18,766 --> 00:38:21,300 With the loss of the roof and no protection 720 00:38:21,300 --> 00:38:25,866 from the elements for almost two years after the fire, 721 00:38:25,866 --> 00:38:29,166 the exposed stone vaulting was repeatedly soaked by rain. 722 00:38:29,166 --> 00:38:32,633 ♪ ♪ 723 00:38:32,633 --> 00:38:36,400 Now protected by the temporary roof, it's drying out. 724 00:38:38,333 --> 00:38:39,700 But as the stones dry, 725 00:38:39,700 --> 00:38:44,166 salts are crystallizing on the underside of the vaulting, 726 00:38:44,166 --> 00:38:46,866 breaking off the outer layers of limestone. 727 00:38:46,866 --> 00:38:51,566 All the damage in this part and on the, on the vault 728 00:38:51,566 --> 00:38:53,666 is a result of the salt. 729 00:38:53,666 --> 00:38:57,833 You can see the loss of matter is two or three centimeters. 730 00:38:57,833 --> 00:39:01,933 This is catastrophic for us. 731 00:39:01,933 --> 00:39:04,266 NARRATOR: In the 18th and 19th centuries, 732 00:39:04,266 --> 00:39:09,633 restorers cast layers of plaster on top of the vaulting 733 00:39:09,633 --> 00:39:12,766 in case of a fire. 734 00:39:12,766 --> 00:39:14,733 This protected the stonework from the heat 735 00:39:14,733 --> 00:39:19,566 of the 2019 inferno, but not from the water used to fight it. 736 00:39:19,566 --> 00:39:22,633 This, along with months of rainwater, 737 00:39:22,633 --> 00:39:25,766 washed salt from the plaster into the lower layers 738 00:39:25,766 --> 00:39:28,033 of the porous limestone. 739 00:39:28,033 --> 00:39:31,400 As the moisture evaporates, the salt crystalizes, 740 00:39:31,400 --> 00:39:35,400 and forces the limestone apart, 741 00:39:35,400 --> 00:39:40,033 destroying the inner surface of the vaulting. 742 00:39:40,033 --> 00:39:43,166 We don't have the original surface of the, of the stone. 743 00:39:43,166 --> 00:39:47,166 It is a real problem from an historical point of view. 744 00:39:48,333 --> 00:39:51,333 NARRATOR: Geologist Véronique Vergès-Belmin 745 00:39:51,333 --> 00:39:56,066 will use a technique to draw the salt out from the stone. 746 00:39:56,066 --> 00:40:02,300 We need to use a material that can absorb the salt 747 00:40:02,300 --> 00:40:05,533 and extract them through capillary forces. 748 00:40:05,533 --> 00:40:09,666 NARRATOR: To extract the salt, Véronique's crew will coat 749 00:40:09,666 --> 00:40:13,800 the vaulting with a paste of clay, sand, and purified water 750 00:40:13,800 --> 00:40:17,600 known as a poultice. 751 00:40:17,600 --> 00:40:20,200 The water from the poultice is drawn into the stone, 752 00:40:20,200 --> 00:40:24,333 where it dissolves the harmful salt crystals. 753 00:40:24,333 --> 00:40:26,766 As the clay of the poultice dries, 754 00:40:26,766 --> 00:40:30,933 it draws the salt water out of the stone, 755 00:40:30,933 --> 00:40:35,733 saving the vaulting from further damage. 756 00:40:35,733 --> 00:40:41,033 The poultices will be removed when they will all have dried. 757 00:40:41,033 --> 00:40:44,100 (tool whirring) 758 00:40:44,100 --> 00:40:46,733 NARRATOR: The restorers chisel away the outer layer of mortar 759 00:40:46,733 --> 00:40:50,566 between the stones to allow the poultice better penetration. 760 00:40:50,566 --> 00:40:53,066 (machinery running) 761 00:40:53,066 --> 00:40:54,833 Next, they load the sticky mixture 762 00:40:54,833 --> 00:41:00,033 into a compressed air gun and spray it into every crevice. 763 00:41:00,033 --> 00:41:01,766 Finally, they carefully 764 00:41:01,766 --> 00:41:03,533 smooth the poultice across the areas 765 00:41:03,533 --> 00:41:07,000 affected by the salt damage. 766 00:41:07,000 --> 00:41:10,866 VERGÈS-BELMIN: You can see that it follows very, very closely 767 00:41:10,866 --> 00:41:12,300 the surface of the stone. 768 00:41:12,300 --> 00:41:14,166 And what we recommend is that 769 00:41:14,166 --> 00:41:16,800 poultice should not be thicker 770 00:41:16,800 --> 00:41:19,566 than half a centimeter to one centimeter. 771 00:41:19,566 --> 00:41:24,533 Otherwise, there are risk that it falls down. 772 00:41:24,533 --> 00:41:26,366 We need to have a very slow process 773 00:41:26,366 --> 00:41:28,800 until the vaults are dry. 774 00:41:28,800 --> 00:41:32,700 But this will take time, much time. 775 00:41:32,700 --> 00:41:38,100 We have to get the cathedral ready in 2024. 776 00:41:38,100 --> 00:41:39,800 This building has to live again. 777 00:41:39,800 --> 00:41:44,166 NARRATOR: The poultice may stay in place until the new roof is built 778 00:41:44,166 --> 00:41:48,733 and the vaulting is permanently protected from rain and snow. 779 00:41:51,133 --> 00:41:54,266 Notre-Dame was built over the course of a hundred years, 780 00:41:54,266 --> 00:41:56,233 section by section, 781 00:41:56,233 --> 00:41:58,166 during the 12th and 13th centuries. 782 00:41:58,166 --> 00:42:02,266 As each new segment of the cathedral was constructed, 783 00:42:02,266 --> 00:42:06,133 another section of timber roof, known as the forest, 784 00:42:06,133 --> 00:42:07,333 was built to cover it. 785 00:42:08,900 --> 00:42:11,700 Hand axes were used to craft each individual beam 786 00:42:11,700 --> 00:42:14,500 in the medieval roof structure. 787 00:42:17,800 --> 00:42:20,000 The fire, which started in the forest, 788 00:42:20,000 --> 00:42:25,700 took just hours to reduce this medieval masterpiece to ashes. 789 00:42:27,300 --> 00:42:29,933 The team will soon begin an unprecedented challenge 790 00:42:29,933 --> 00:42:34,366 to rebuild the forest in under two years. 791 00:42:34,366 --> 00:42:36,233 FROMONT (translated): We're going to reuse techniques 792 00:42:36,233 --> 00:42:38,600 that are extremely similar to what was used, 793 00:42:38,600 --> 00:42:40,733 because it's technically necessary, 794 00:42:40,733 --> 00:42:43,966 and if we don't do that, the wood will behave differently. 795 00:42:43,966 --> 00:42:48,166 NARRATOR: The spire lost in the fire was erected in the 19th century. 796 00:42:48,166 --> 00:42:51,900 These beams were cut with saws. 797 00:42:51,900 --> 00:42:55,900 So today, Rémi's carpenters will use modern saws 798 00:42:55,900 --> 00:42:59,266 to cut the new spire beams. 799 00:42:59,266 --> 00:43:02,100 FROMONT (translated): We have extremely rigorous rules that are the highest 800 00:43:02,100 --> 00:43:04,100 that can be had in carpentry, 801 00:43:04,100 --> 00:43:05,733 because Notre-Dame is absolutely exceptional 802 00:43:05,733 --> 00:43:08,833 in terms of wood quality. 803 00:43:10,333 --> 00:43:13,466 NARRATOR: This sawmill in Normandy processes over 804 00:43:13,466 --> 00:43:16,666 a million cubic feet of timber each year. 805 00:43:16,666 --> 00:43:21,300 It's one of 45 sawmills across France that has answered 806 00:43:21,300 --> 00:43:24,466 the call to cut beams for Notre-Dame's spire. 807 00:43:24,466 --> 00:43:26,800 (translated): For us, it's a chance to prove our dynamism 808 00:43:26,800 --> 00:43:30,100 and show that French forests can help rebuild this structure-- 809 00:43:30,100 --> 00:43:31,766 one of the jewels of France. 810 00:43:31,766 --> 00:43:35,000 I do this as a form of philanthropy-- it's for free. 811 00:43:37,833 --> 00:43:39,533 NARRATOR: The team wastes no time 812 00:43:39,533 --> 00:43:42,366 in getting to work on the beams. 813 00:43:42,366 --> 00:43:44,933 First stop: the debarker. 814 00:43:44,933 --> 00:43:48,233 ♪ ♪ 815 00:43:48,233 --> 00:43:50,466 This machine strips off the outer layers, 816 00:43:50,466 --> 00:43:55,133 removing the loose bark. 817 00:43:55,133 --> 00:43:58,300 Now the one-ton tree trunk enters the sawmill 818 00:43:58,300 --> 00:44:01,533 and rolls onto the saw carriage. 819 00:44:02,566 --> 00:44:03,966 FEILLET (translated): On this joystick, 820 00:44:03,966 --> 00:44:06,566 we have buttons that allow you to do operations 821 00:44:06,566 --> 00:44:10,533 like log loading or what is called slabber chipping. 822 00:44:10,533 --> 00:44:14,100 The slabber is the first machine before the blade, 823 00:44:14,100 --> 00:44:16,700 which shreds away the outer part of the log. 824 00:44:18,800 --> 00:44:21,033 NARRATOR: The bandsaw blade 825 00:44:21,033 --> 00:44:23,400 is a high-speed loop of steel that runs at 826 00:44:23,400 --> 00:44:26,833 140 feet per second. 827 00:44:29,133 --> 00:44:32,266 François removes inch-thick slices to trim the beam down 828 00:44:32,266 --> 00:44:33,366 to the dimensions requested 829 00:44:33,366 --> 00:44:36,100 by the Notre-Dame architects. 830 00:44:36,100 --> 00:44:39,733 ♪ ♪ 831 00:44:39,733 --> 00:44:42,300 FEILLET (translated): What I enjoy most is discovering the wood. 832 00:44:42,300 --> 00:44:43,966 Each tree is unique. 833 00:44:43,966 --> 00:44:45,433 Ultimately, it's a game of strategy 834 00:44:45,433 --> 00:44:46,933 you play with each tree. 835 00:44:46,933 --> 00:44:49,533 It's never the same thing-- it's something new every time. 836 00:44:49,533 --> 00:44:53,666 ♪ ♪ 837 00:44:53,666 --> 00:44:57,033 NARRATOR: The beams from François's sawmill are stacked, 838 00:44:57,033 --> 00:44:59,433 ready to join more than a thousand others 839 00:44:59,433 --> 00:45:03,733 coming from across France for Notre-Dame's new spire. 840 00:45:03,733 --> 00:45:06,233 (translated): A sawmill like ours, we will not do anything 841 00:45:06,233 --> 00:45:08,233 like this again in our lives. 842 00:45:08,233 --> 00:45:12,233 We'll go down in history for having modestly contributed, 843 00:45:12,233 --> 00:45:13,566 like everyone working on Notre-Dame, 844 00:45:13,566 --> 00:45:16,266 to restore this cathedral-- our cathedral. 845 00:45:16,266 --> 00:45:19,833 ♪ ♪ 846 00:45:19,833 --> 00:45:22,800 NARRATOR: Inside Notre-Dame, the first chance 847 00:45:22,800 --> 00:45:25,800 to get up close to the gigantic south rose window 848 00:45:25,800 --> 00:45:27,800 in 160 years... 849 00:45:27,800 --> 00:45:29,900 (speaking French): 850 00:45:29,900 --> 00:45:33,466 NARRATOR: ...has revealed a mystery. 851 00:45:33,466 --> 00:45:38,200 We only have 13th-century glass and 19th-century glass. 852 00:45:38,200 --> 00:45:39,466 In the 19th century, 853 00:45:39,466 --> 00:45:43,933 they removed everything that wasn't 13th century, 854 00:45:43,933 --> 00:45:46,033 and then they had to do new panels 855 00:45:46,033 --> 00:45:47,433 if a panel was missing. 856 00:45:47,433 --> 00:45:51,233 ♪ ♪ 857 00:45:51,233 --> 00:45:54,500 NARRATOR: The chief suspect for these radical changes to the window 858 00:45:54,500 --> 00:45:59,366 is architect Eugène Viollet-le-Duc. 859 00:45:59,366 --> 00:46:03,166 In the 1840s, he was tasked with breathing new life 860 00:46:03,166 --> 00:46:05,266 into Notre-Dame. 861 00:46:05,266 --> 00:46:09,900 At the time, it was not the beloved building we know today. 862 00:46:09,900 --> 00:46:12,166 The cathedral was ransacked during the French Revolution, 863 00:46:12,166 --> 00:46:17,200 statues of biblical kings on the façade were decapitated, 864 00:46:17,200 --> 00:46:19,633 and it was used as a warehouse, 865 00:46:19,633 --> 00:46:23,233 sitting derelict and unloved for decades. 866 00:46:23,233 --> 00:46:26,833 Over the course of 20 years, 867 00:46:26,833 --> 00:46:30,266 le-Duc reinstated the statues of the façade, 868 00:46:30,266 --> 00:46:32,866 rebuilt the sacristy, 869 00:46:32,866 --> 00:46:35,700 designed hundreds of new gargoyles, 870 00:46:35,700 --> 00:46:42,133 and raised the 210-foot spire. 871 00:46:42,133 --> 00:46:43,833 OWUSU: Viollet-le-Duc, God bless him, 872 00:46:43,833 --> 00:46:48,633 would have been what we consider to be a starchitect, you know? 873 00:46:48,633 --> 00:46:50,366 He was a man who knew his mind, 874 00:46:50,366 --> 00:46:53,166 he was a man who was highly respected, really determined, 875 00:46:53,166 --> 00:46:56,300 and saw himself as a powerful leader. 876 00:46:56,300 --> 00:47:01,600 NARRATOR: And he used his power to make some puzzling changes. 877 00:47:01,600 --> 00:47:05,666 During his restoration, le-Duc removed all glass 878 00:47:05,666 --> 00:47:07,733 in the south rose window that was not original 879 00:47:07,733 --> 00:47:12,666 and replaced it with modern glass. 880 00:47:12,666 --> 00:47:13,800 Elisabeth is also finding 881 00:47:13,800 --> 00:47:17,200 that he made significant alterations to some 882 00:47:17,200 --> 00:47:19,333 of the original glass panels. 883 00:47:19,333 --> 00:47:21,533 (translated): Look at this little martyr-- 884 00:47:21,533 --> 00:47:24,500 it looks like she was cut. 885 00:47:26,433 --> 00:47:28,566 She's missing the colored lines around the edge. 886 00:47:28,566 --> 00:47:31,966 The halo is slightly cut here, and her feet are cut, too. 887 00:47:31,966 --> 00:47:35,933 Maybe she has been moved within this window. 888 00:47:35,933 --> 00:47:41,066 (speaking French) 889 00:47:41,066 --> 00:47:44,200 NARRATOR: Why did le-Duc alter the window? 890 00:47:44,200 --> 00:47:45,966 Was he trying to impose his own design? 891 00:47:48,100 --> 00:47:50,266 ♪ ♪ 892 00:47:50,266 --> 00:47:51,700 The glass experts hunt for clues 893 00:47:51,700 --> 00:47:56,666 here, at the Paris Médiathèque of Architecture and Heritage. 894 00:47:56,666 --> 00:47:57,966 They hope le-Duc's plans 895 00:47:57,966 --> 00:48:02,500 for the south rose window shed light on his thinking. 896 00:48:02,500 --> 00:48:06,633 BOULANGER (speaking French): 897 00:48:08,100 --> 00:48:10,833 NARRATOR: As they dig into the archives, they make a breakthrough. 898 00:48:12,300 --> 00:48:16,333 BOULANGER: We just discovered that there was a change of structure. 899 00:48:16,333 --> 00:48:18,800 Before Viollet-le-Duc, there was an iron reinforcement 900 00:48:18,800 --> 00:48:23,500 in the center of the rose, but obviously it wasn't enough. 901 00:48:23,500 --> 00:48:27,366 So Viollet-le-Duc put it further away from the center. 902 00:48:27,366 --> 00:48:30,466 And when you removed the ironwork here, 903 00:48:30,466 --> 00:48:33,033 he had to change the form of the panels. 904 00:48:34,666 --> 00:48:37,133 NARRATOR: Le-Duc's restoration was sweeping. 905 00:48:37,133 --> 00:48:39,666 ♪ ♪ 906 00:48:39,666 --> 00:48:42,133 He removed a smaller structural ring of iron 907 00:48:42,133 --> 00:48:43,766 and replaced it with a bigger ring 908 00:48:43,766 --> 00:48:48,533 to strengthen the core of the window. 909 00:48:48,533 --> 00:48:52,066 He removed all traces of previous restorations 910 00:48:52,066 --> 00:48:56,533 to replace them with panels of new glass. 911 00:48:56,533 --> 00:49:01,400 And he rotated the whole window 15 degrees 912 00:49:01,400 --> 00:49:06,000 to make it structurally stronger. 913 00:49:06,000 --> 00:49:09,500 The problem must have been that the medieval rose 914 00:49:09,500 --> 00:49:13,333 wasn't stable in its axis. 915 00:49:13,333 --> 00:49:15,000 That must have been the problem. 916 00:49:15,000 --> 00:49:17,500 That's very interesting. 917 00:49:17,500 --> 00:49:19,666 ♪ ♪ 918 00:49:19,666 --> 00:49:22,466 NARRATOR: Le-Duc's major changes to the south rose 919 00:49:22,466 --> 00:49:27,100 were motivated by more than mere aesthetics. 920 00:49:27,100 --> 00:49:29,066 Strengthening the window has helped preserve 921 00:49:29,066 --> 00:49:32,433 this masterpiece. 922 00:49:32,433 --> 00:49:36,300 We don't come across this kind of new information every day. 923 00:49:36,300 --> 00:49:40,366 ♪ ♪ 924 00:49:40,366 --> 00:49:42,000 NARRATOR: Thanks to the scaffolding, 925 00:49:42,000 --> 00:49:44,000 these historians and scientists 926 00:49:44,000 --> 00:49:45,866 are painting an intimate portrait of how 927 00:49:45,866 --> 00:49:47,300 the south rose window, 928 00:49:47,300 --> 00:49:50,100 one of the wonders of this cathedral, 929 00:49:50,100 --> 00:49:52,566 evolved to survive. 930 00:49:56,933 --> 00:50:00,400 ♪ ♪ 931 00:50:00,400 --> 00:50:01,433 Three years into the ambitious 932 00:50:01,433 --> 00:50:04,133 five-year restoration project, 933 00:50:04,133 --> 00:50:06,066 the team at Notre-Dame has already 934 00:50:06,066 --> 00:50:08,900 stabilized the structure, 935 00:50:08,900 --> 00:50:10,533 the process to free the cathedral 936 00:50:10,533 --> 00:50:12,166 from the toxic lead is underway, 937 00:50:12,166 --> 00:50:17,266 and two "test chapels" have been fully restored. 938 00:50:17,266 --> 00:50:19,633 MARIE PARANT (translated): We are very surprised by the quality of the materials. 939 00:50:19,633 --> 00:50:21,533 They used beautiful pigments, 940 00:50:21,533 --> 00:50:24,633 gold of very good quality-- a very beautiful technique. 941 00:50:24,633 --> 00:50:28,933 NARRATOR: Here, mural painting and stonework restoration techniques 942 00:50:28,933 --> 00:50:29,966 have been tested. 943 00:50:29,966 --> 00:50:32,466 They will be replicated throughout 944 00:50:32,466 --> 00:50:33,533 the rest of the building. 945 00:50:33,533 --> 00:50:35,833 PARANT (translated): In the long term, 946 00:50:35,833 --> 00:50:38,466 it's to optimize the restoration of all the other chapels. 947 00:50:38,466 --> 00:50:39,566 We're very happy. 948 00:50:39,566 --> 00:50:42,566 We feel that we've played our part. 949 00:50:42,566 --> 00:50:43,733 It's really the first step 950 00:50:43,733 --> 00:50:46,166 towards the complete restoration of Notre-Dame. 951 00:50:46,166 --> 00:50:52,166 ♪ ♪ 952 00:50:52,166 --> 00:50:55,833 NARRATOR: But there's still a long way to go. 953 00:50:55,833 --> 00:50:58,333 Rebuilding the vaulting, the roof, 954 00:50:58,333 --> 00:51:03,366 and the spire identically will be a monumental task. 955 00:51:03,366 --> 00:51:08,266 (translated): It's extremely ambitious work, considering the schedule. 956 00:51:08,266 --> 00:51:09,966 (translated): We have a huge responsibility 957 00:51:09,966 --> 00:51:11,866 to the generations of today and the future. 958 00:51:11,866 --> 00:51:14,566 ♪ ♪ 959 00:51:14,566 --> 00:51:17,700 NARRATOR: Meanwhile, historians and scientists 960 00:51:17,700 --> 00:51:19,566 are rewriting our understanding 961 00:51:19,566 --> 00:51:23,266 of the very fabric of this medieval wonder. 962 00:51:23,266 --> 00:51:25,266 ♪ ♪ 963 00:51:25,266 --> 00:51:26,633 It opens new perspective. 964 00:51:26,633 --> 00:51:31,100 That's a huge opportunity. 965 00:51:31,100 --> 00:51:34,200 OWUSU: Tragic as the fire was, 966 00:51:34,200 --> 00:51:37,933 I think it took something like that to make us understand 967 00:51:37,933 --> 00:51:44,566 just what an absolutely amazing work of collaborative genius 968 00:51:44,566 --> 00:51:47,800 that building was. 969 00:51:47,800 --> 00:51:50,066 WOMAN: Notre-Dame is Notre-Dame. 970 00:51:50,066 --> 00:51:52,500 (chuckling): We definitely need it back. 971 00:51:52,500 --> 00:51:54,566 ♪ ♪ 972 00:51:54,566 --> 00:51:57,633 NARRATOR: The last chapter of this extraordinary endeavor 973 00:51:57,633 --> 00:52:03,533 has begun: to return Notre-Dame to France and the world. 974 00:52:03,533 --> 00:52:08,100 ♪ ♪ 975 00:52:31,966 --> 00:52:39,500 ♪ ♪ 976 00:52:46,733 --> 00:52:51,600 ANNOUNCER: To order this program on DVD, visit ShopPBS. 977 00:52:51,600 --> 00:52:54,333 Or call 1-800-PLAY-PBS. 978 00:52:54,333 --> 00:52:57,200 Episodes of "NOVA" are available with Passport. 979 00:52:57,200 --> 00:53:01,000 "NOVA" is also available on Amazon Prime Video. 980 00:53:01,000 --> 00:53:06,200 ♪ ♪ 981 00:53:15,000 --> 00:53:22,166 ♪ ♪