The line embodies the explicit action or movement, the ground the implicit. Whereas the line is the once and only component, the full expanse of canvas is a continued presence that has been worked on over a long time span during which multiple layers of egg tempera and oil paint are built up until the surface begins to resonate and is filled with life. Within this created history the linear element takes its designated place. When the fusion of line and ground are successful the finished painting is both immediate and timeless, embedded in a common history or universal visual vocabulary that precedes language and intellectual persuasion.
I often use a 4cm thick stretcher in combination with a 2cm one. I do this to explicitly and physically bring the painting into the room.