Blackout Fabric

Blackout fabric is woven or coated so that essentially no light passes through the material itself — hold it to a lamp and you see nothing. The crucial, often-buried truth is that blackout describes the fabric, not the installed result: mounted inside a window frame, a blackout shade still leaks daylight around its sides and bottom through the deduction gap, so the room is dark-ish, not dark. Achieving a genuinely dark room takes more than fabric — an outside mount with generous overlap, side channels, or a dual-shade setup. Honest coverage always separates the fabric claim from the installed outcome, because that gap is where buyers feel misled.