Why does my blockout curtain show pinholes of light at the seams?
Pinholes of light along the seams of a blockout curtain are needle holes. Sewing a self lined blockout fabric punches through the blockout coating, so light comes through wherever the stitching runs, most of all in direct sun. A separate blockout lining behind the face fabric conceals them.
A self lined blockout gets its blocking performance from a coating on the fabric. Any seam or hem means a needle goes through that coating, and every needle penetration is a hole the coating no longer covers.
They're most obvious with strong direct sun behind the stitch line, and they can become more noticeable over time as the holes open up slightly with handling and movement.
What conceals them
Add a separate blockout lining behind the face fabric. A second layer that isn't stitched in the same places covers the pinholes in the first. Different thread, finer needles and tighter stitching all still make holes.
This answer is general information. For your own windows, your retailer's advice and your order with them come first.
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