These Collages are also on recycled cardboard, but I did two layers of plaster. The first was pretty thin, then painted with acrylics, sealed with GAC-100, then another layer of plaster and acrylics, then sanded and removed in some areas to reveal the previous layer. More paint and then collaging with painted old book pages.
This collage was created as the one above, using a Gelli-printed vellum paper. Some scribbles with pens. Time to cut up some more boxes.