Dupion silk is produced from two or more silkworms that spin a cocoon together. This makes a strong double and durable-thread silk, usually resulting in a rough yarn and irregularity in sheerness or weight. Black specks that occasionally appear in the fabric are part of the original cocoon of the silkworm. Removing all of them would weaken the fabric. They are inherent to dupion silk fabric and should not be considered as defects in silk duvet.