First of all I have poured and modeled with the still wet polyurethane, and I have carefullied lay down it on the plexiglass. In position on the background, still fresh, I have still poured sand over. Erik I have not used layers of clear epoxy mixed with sand, just foam and natural materials but at the end I have given one hand of impermeable varnish.
The background is solid and rigid but I succeed to fix the plants and to make them to grow on the wall...
I hope that you have understood (my english is a little bit poor...
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