Wedi board (pronounced "weedy") is an ideal substrate for mosaic artists. It consists of styrofoam encased in mesh and cement. This sturdy material is very lightweight and cuts easily with a utility knife (no need for any power tools!). Wedi Panels are about ¼ of the weight of Durock and other cement boards, and ½ the weight of MDF or birch plywood.
It is rigid, waterproof, and weatherproof. It does not warp, does not require sealing, and can be used on floors, walls, and as art panels. It is made of a middle core of blue styrofoam with a reinforced polymer modified concrete coating on both sides. The foam core center makes it lightweight. You can use Weldbond, silicone, thinset, Mac glue, etc.
How To Hang
Because of the foam core, washers are required when attempting to screw into or through the panel. Without washers, the screws or nails would go straight through the panel. ‘Wedi Washers’ are specifically made for this purpose. Wedi Washers have four prongs that press easily into the Wedi, with a center hole for an 8 gauge nail or screw. When fully installed, the washer sits about 1/32” above the surface of the Wedi and can be mosaiced over. Standard washers can be used as well.
Here's the back of the washer with the picture hook attached. Notice that the cement is cracking a little - that's OK. It's the only way to get the front to lie flat.
There is also wall hangers. The plastic piece screws into the wall. You then place the screw on the wedi board & then screw into the plastic piece into the wall. You will mosaic on the board on the wall.
Either way, you have to have your hangers in place before you start to mosaic.
Where To Buy
See http://www.wediusa.com/ for local distrubutors. I was fortunate in that a supplier was 20 minutes from my home & bought a 3' x 5' sheet of wedi.