Slitherine

If you folded tape over the edges of the card before you textured it that would work but you would struggle to retro fit it to this which is a pity.

lonehorseman wrote:It warps the carboard I think I will redo it with Balsa and an MDF base

Mix used (wet) coffeegrounds with acrylic paint or medium into a thick spackle and dab it in in several small increments. Sort of like grog in clay ( http://pottery.about.com/od/potterygloassary/g/grog.htm ) , the coffee grounds limit the shrinkage areas to the acrylic matrix, resulting in little or no distortion, and minimal added weight.