Ah! I am a beginner, and use a much thinner quilting cotton. To prevent the glue showing I have to fill with mix of acrylic medium and starch paste (haven’t found a ratio I really liked), or to back the cloth with paper. So to me your casing looked like witchcraft! I really like the etching effect. No idea how it’d work in practice, but it seems like you could make some gorgeous illustrationy covers by going over the cloth multiple times at different strengths for different values.

Ty for the post! Did you media fill the bookcloth with anything? What glue did you use?