Starting a New Black and White Painting

I've been working on tall thin canvases, 10" x 48" in size, and making a group of four that are not too dissimilar so that people might hang them together or at least in the same room if they care to.  My basic procedure in these four has been to paint the canvas all white and then when it's dry, to cover sections in painter's tape.  Then I paint the canvas all black around the tape.  When I take the tape off, I have this:

  Tall Black & White #3, 10" x 48" acrylic on canvas.

Next, I drew lines in a "scribbling" effect, using white on the black and black on the white:

  Tall Black and White #3, 10" x 48" acrylic on canvas.

After everything is dry, I will work on this again.  Meanwhile, here's what my fourth canvas looks like at the second stage:

  Tall Black & White #4, 10" x 48" acrylic on canvas.