CECIL BALMOND
If you normally put brick upon brick, and if you just go up vertically, you er we all know that works, but if you start going on the slope that's that's very difficult and Brunelleschi came up with the brilliant idea of a herringbone pattern, that it it's, it's common sense in a way, but it's the intuition of an engineer at work definitely.

NARRATOR
Many investigations had used the herringbone brickwork to explain Brunelleschi's achievement. But for Massimo it wasn't enough. How had the bricks been laid in such a complex pattern? And how had the shape of the dome been preserved without any scaffold to guide it?

The maverick architect had struggled for years to arrive at a solution.

MASSIMO RICCI
Actually studying a problem, such a difficult and complex question, will bring a person to the point where he is confronted by night after night of studies which seem to pass in a few minutes.
Brunelleschi too, faced with the same problem, would certainly have done the same thing.

NARRATOR
Did Massimo's obsession really bring him any closer to Brunelleschi? Faced with academic sceptics Massimo pressed on with his experiments. How had his hero actually built the dome?

SIMON PEPPER
The fact that Brunelleschi was able to do this without using centring was what seems to have struck his contemporaries as the greatest part of the achievement.

NARRATOR
Like the original, Massimo's dome has a light scaffold around its edge for the builders work from - but there's no forest of supporting timber propping up the walls from the ground, and no template to give it its shape.

Brunelleschi was a genius. He knew enough geometry to describe the shape of the dome, but how could he build it? He needed a trick simple enough to be used by ordinary bricklayers working at perilous heights. The minute positioning of every single brick was vital.

The first important system invented by Brunelleschi was for the substitution of the large centrings, total centrings, with small ones, like these.

Obviously there had to be a trick to do this.

Well, the trick is this simple plumb-line that I have here, and these two ropes which in fact are for making this centering vertical which in turn is held in place with these hooks that you can see.

These hooks were also found in the real dome.

NARRATOR
By making sure that the small wooden centrings were correctly aligned, the profile of the dome could be traced in stages. Some experts had suggested similar devices before, but Massimo knew he was still only just beginning to understand Brunelleschi's system. The wooden centring didn't explain how the complicated pattern of bricks could fill the spaces between the corners of the dome.

And the angle of these bricks was critical. Too flat, and the geometry wouldn't work - too steep and the bricks would fall before the mortar had set. There had to be something more. At last Massimo discovered Brunelleschi's secret. The most important invention of the dome.

MASSIMO RICCI
After about fifteen years, I managed to build the flower and from that moment on it was all a… well, a continuous discovery.

NARRATOR
A flower! Massimo believes that Brunelleschi drew a pattern of petals where the dome was to spring from the tops of the cathedral walls base of the dome. This precise mathematical form then became a key to position every single brick in the construction.
Its brilliant in its simplicity.

MASSIMO RICCI
It has taken twenty years of my life to discover this simple metal flower which solves the dome's construction problems. This is the real secret of the dome of Santa Maria del Fiore.

This simple metal flower, which allows such perfect orientation, as you can see, of all these difficult bricks we have here.
This simple wire enables the bricklayers to place them so perfectly.
There would have been no other way of doing it.

NARRATOR
Once the flower pattern is fixed all you need are ropes leading from the pattern at one end, to the top of the wall on the opposite side.
A line is adjusted along the flower until it passes through the centre point of the dome.
This allows a bricklayer, holding the other end of the rope, to line up each brick at a slightly different angle preserving the dome's overall shape.

The curve of the walls demonstrates that the flower pattern works. But how could historians be sure that Brunelleschi used the same technique? The search was on for a piece of historical evidence.

Was there anything that linked Massimo's flower theory to Brunelleschi's dome?

A document in the Florence archives, for centuries thought to be a casual sketch of the dome, was brought to the centre of a historical debate.

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Content last updated: 29/03/2005

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