A technique that dates back 5,000 years or more, buon fresco―or true fresco―involves the application of five layers of plaster made from a mixture of slaked lime and sand. The first three layers can take 10 days to dry. Then come the last two layers.
Vigil paints onto the final, fifth layer, known as the intonaco, while it's still wet. He grinds pigments to a fine powder, then brushes them onto wet plaster, following the outlines of his sketches transferred earlier. The paint is absorbed into the damp wall, resulting in luminous, durable hues.
The project's scale means that Vigil can use a wider range of brushes and strokes, often working with his whole arm rather than his wrist. Still, fresco is unforgiving. Make a mistake and the section must be completely scraped off, replastered, and repainted. And El Torreón's height and concave walls mean that perspective changes. More than once, Vigil has stood on the tower's floor after completing sections near the ceiling only to realize that they didn't work when seen from below.
In the project's early days, Vigil had to rely on ladders and scaffolding to reach the upper tower. Now he also uses a lift outfitted with a weight bench, on which he can recline comfortably as he paints. But his lift is wobbly too, and for a while Vigil didn't notice that he was gripping with his feet, putting such pressure on them that the nails on his big toes fell off.