Blockout

Blockout, or sometimes called blackout, is a specially designed fabric that is made to ‘block’ all light from shining through the material. This material also stops the light that hits the back of the fabric from shining through to the other side. The backside is often black or grey but new developments have made it possible to have the backside painted white. 

Products for double sided print also have a blockout "layer" in the middle of the material.