The curtains are a nice heavy velvet. They block out most of the light. I don’t think that curtains would ever be 100 black out because the light still comes in over the top and if you have more than one panel, as I do, light leaks in through the sides. If you want 100 blackout, get a shade that fits inside the window frame and then get blackout curtains to cover that. I love these curtains. The way we hung them makes the room feel bigger and makes it feel more like a home. The room is darker in person than in this photo.