Here's how he did it:
1. Photography: Close first took a large-scale photograph of Bob, which he then divided into a grid of squares.
2. Transfer: He transferred this grid onto the canvas, creating a corresponding grid of squares on the surface.
3. Square by Square: Close then painted each square individually, focusing on the values (light and dark) and colors within each section.
4. Overall Effect: By meticulously working on each square, Close gradually built up the entire portrait, creating a detailed and realistic depiction of Bob.
It's important to note that while the grid helps with accuracy and scale, it's not the only tool Close used. He also employed various painting techniques, including impasto (thick layers of paint) and sgraffito (scratching into the paint) to create texture and depth in his work.