Here is my first attempt at the working in reverse exercise.

This was challenging but quite interesting, working just with the eraser and applying tone made it feel a bit like painting.
I liked the picture best in fact in the earlier stages, not as it turned out above, even with inaccuracies in the form of the teapot. I did find it difficult getting the form right, and had to keep reworking, erasing, adding tone, re-erasing. I think parts of the teapot, such as the handle, are better drawn this time, but I wonder if that’s just because of a second attempt at the same objects.
The original drawing of the teapot and apple in the ‘Observing light and shadow’ exercise, appears smoother now I look at it, and the application of tone is more accurate – the teapot was in fact a dark red colour. The shapes were also drawn more accurately in the original picture. Here it is again to act as a point of contrast to the above:

The working from dark to light approach in the current exercise, just focusing on tone, did force me to look more carefully.
I think a discovery during this current exercise was regarding lines. Why draw with lines? Well, without being able to use them, I missed them. I realise they help me to relate objects to one another and provide scaffolding. But I also started to wonder how perhaps lines dominate the way I draw, my drawing all becomes scaffolding with a bit of added tone. Perhaps I could use lines more lightly and sparingly, just to lay out proportions and positions on the page. It’s something I will explore over the coming month.
Anyway, the above was a first attempt, perhaps it is overdrawn a bit. I don’t know if perhaps I rubbed out too much, so rubbing out whole lighter areas rather than just highlights and redrawing over those, and this was exacerbated by inevitable mistakes, so that rubbing out was also about correcting and not just picking out lighter tone. Perhaps preliminary short sketches might help a bit in similar future studies.
In terms of the size of paper, I much prefer working on a larger sheet when concentrating on varying tone. I feel you need the larger space to get across the slight changes in tone better. Besides, it felt freer to work on a larger sheet of paper, particularly in the working in reverse exercise.