A、80 new dragons were 3D-printed. B、All the dragons were painted by master craftsmen. C、It took about 18 hours to print each of

When the Chinese pagoda in Kew Gardens was completed in 1762, it was the second tallest building in England designed by architect William Chambers who made several visits to China. The tier tower stood nearly 50 meters high with 80 colorful dragons resting on the roofs of its ten storeys. Polly Putnam, curator of Historic Royal Palaces says eighteenth-century Londoners were horrified.
    “Westerners had never seen Chinese architecture like this before and so it kind of blew their minds because it was so different from anything Chinese they’d ever experienced.”
    While pagodas are traditionally used as places of worship, the Georgian royal family used the structure to entertain visitors and share views of London. But about 20 years after its completion the pagoda’s wooden dragons disappeared. No one is sure of the true explanation.
    “What I think happens was actually they were 20 years old. Britain was in a mini Ice Age at that time, so there was an awful lot of frost. There was an awful lot of storms. There was even a volcano which exploded, erupted in 1783 covering London in smoke. 20,000 people died and so the year after I can imagine that the dragons were looking pretty shabby.”
    A restoration project began in 2014 to return the pagoda to its former glory. Experts consulted original design, drawings, paintings and a book written by Chambers to ensure the new dragons wouldn’t succumb to the elements.
    They were 3D-printed. South Carolina-based 3D system used a process called precision laser to produce 72 new dragons. The 8 snake-like creatures on the lowest roof were hand-carved and painted by master craftsmen. Each dragon took about 18 hours to print, using a durable nylon material.
    “So perfect use, really because it solves a lot of problems. We got to make it lightweight which means hollow inner part but we still need to build internal structures into the dragon which is very difficult, almost impossible to do any other way. 3D-printing is a very fast way of making very complicated, unique pieces.
    There are 18 versions of a dragon on the building so we can manage all that and print it very, very efficiently and we can scale up on the printing side as well to make sure it’s done to the program. The result is like stepping back to an earlier time in a royal garden that is a UNESCO World Heritage Site.”
    Question 19. What do we learn about the Chinese pagoda in Kew Gardens?
    Question 20. About what time did the pagoda’s wooden dragons disappear?
    Question 21. What do we learn about the restoration of dragons on the tower?