Step 12: Apply the silicone to the back
Next apply the silicone to the back of the background. Dont be shy about this step and add lots of silicone. Even though it has cement on it, these things still float like life preservers so dont get skimpy here. I ran a 1/4 inch bead about every 1/4 to 1/2 inch across. I dont know if it makes a difference but I ran the silicon lengthwise along the pieces.