This painting is a prime example of pentimento, as grid lines can be seen throughout the painting, as Vasari didn’t omit the grid outline definition. My art teacher, Ryan Shultz, speculates that due to this error, Vasari abandoned work on this painting, as no matter how many layers he’d paint over, the grid would always be there, and never go away. Even if he managed to cover it up, years later, the grid lines would end up being prominent and noticeable as they now are.