#33 Brunelleschi & The Dome IV

* So what was the magic solution that Bruno brought to the Dome on August 7, 1420? * How do you build a dome out of bricks, that curves upwards, with no support, that won’t fall down? * Well he actually invented not one, not two, but a handful of new tricks. * And this is even BEFORE he invented linear perspective. * The first thing I want to talk about is called In Italian – (”Spina di Pesce”)  – spine of the fish. * In English we call it Herringbone * A Zig zag pattern. * His idea was to zigzag the bricks. * If you have all of the bricks lying horizontal, the forces are all pushing in a single direction. * But if you stick a vertical brick in there every few bricks, it pushes back on the horizontal forces. * If you climb the dome, you’re actually walking in between the inner and the outer domes. * And in certain sections, where there isn’t any plaster on the walls, you can actually see the zigzag pattern. * This was so original, Bruno not only needed to convince the board of the committee, he needed to convince the workers that it wouldn’t all fall down on them . * They were working 230 feet in the air. * If the bricks fell down on them, it was certain death. * How did he make them trust him? * That 12 foot high demo dome we talked about last time – in the car park of the Duomo museum.. * Another thing is that if you could take off the outer layer of tiles and look at the dome brickwork, you’d notice that the Spina di Pesce patterns follows the dome around each side like a spiral – so it becomes a single dome, not 8 sides. * This apparently spreads out the forces, making it more stable. * Very stable. * Like Trump. A very stable genius. * Where exactly Filippo learned of the herringbone bond is one of the dome’s unsolved mysteries. * The herringbone pattern had of course been known to masons and bricklayers for many centuries. * The Romans made extensive use of something they called opus spicatum, literally “spiked work” * and the pattern is also found in the half-timbered brick walls of Tudor houses in England. * In both these cases, however, it is decorative rather than structural; * the Romans used it only in ornamental paving on the floors of their villas. * However – systems of interlocking brickwork similar to that in the dome can be found in certain Persian and Byzantine domes, which leads some scholars to think that Filippo may have visited these lands during his Rome years. * Another trick he used to make it more stable is that if you looked at the bricks from corner to corner you’d see they form a downward arch. * Higher in the corners, lower in the centre of each wall. * This pushes the weight downwards. * Like you pushed me downwards in Vegas. * But there’s another great story about the zigzag pattern. * I said earlier that when you climb up the staircase, some sections aren’t covered in plaster? * Well apparently that was deliberate. * In the sections that Bruno didn’t plaster over, the amount of mortar between the bricks is way too small to contain the forces of the bricks. * But in sections where the plaster has chipped away over the centuries, you can see the right amount of mortar has been used. *