Antonio Mancini (1852-1930), whom Sargent called “the best living painter,” used a unique Grid system for sight-size Painting.
Mancini's system has been called the "graticola" or the "raster." It involved a network of strings stretched across a frame between the artist and the model, and a corresponding set of strings, exactly the same size, stretched directly on top of the painting itself.
Mancini said the system was not his own, but was adapted from an old master, presumably basing it on the Durer Grid or on Leonardo's notebooks.
By looking through the grid of strings, and then painting what he saw in each of the spaces between the strings, he could match painted reality to observed reality.
The system required that the sitter remain exactly in the same position, and that Mancini always observe the model through one eye from a specific point in three-dimensional space.
According to a witness in 1893, "He always works at a distance from his canvas, always returning to sit at precisely the same little spot that he carefully marked on the floor."
He observed the painting and the model together, then advanced quickly and attacked the canvas to correct a small spot and make it match the values of subject.
Many of the paintings bear the imprint of the grid. Presumably there would be a point in the process where you would lift the frame off the painting and blend together the patches to get rid of the lines.
But reportedly Mancini liked leaving a hint of the squares because it endowed the paintings with a sense of objectivity and scientific accuracy.
Even though Mancini's paint technique can often be loose and gestural, there's a sense of objective realism hovering behind it.
Mancini was a proponent of the Verismo movement, an Italian response to the striving for Realism in France.
Mancini was passionate about his use of the tool, saying “the advantages I derive from it are unlimited.”
I've selected samples that show the influence of the grid, but to be fair, many of his other paintings don't show the evidence of the process.
In addition to the horizontal and vertical strings, he also used diagonal grid lines. Sitters reported that he added strings to the grid during the painting process.
Presumably the diagonal strings helped him locate individual squares and they also gave additional bounding lines to compare to the form.
For all the precision and objectivity of his method, Mancini was in extreme emotional states during the process of painting: "at one moment he is grieved to his soul, then he is singing happily- then livid and wild- every square of tone shows what you get out of him- every little square he paints is another little piece of his sanity lost- it won’t be long before he runs out. I hope that I’m mistaken in this, but… the great genius that leads to madness tosses and turns in his head incessantly."
Mancini's Graticola by Matthew Innis (more on sources of quotes)
Juan Ramirez did a Kickstarter project to reconstruct the graticola
Carolyn Anderson's blog "Fractals, Chaos, and Mancini's Graticola"
Antonio Mancini on Lines and Colors
Wikipedia article on Mancini
Thanks to Darren Rousar for telling me about the graticola.
Exhibition Catalog: Antonio Mancini: Nineteenth-Century Italian Master (Philadelphia Museum of Art)