- Dust, ash, scurf, small vein and other elements that mixed inside the feather and down.
- Judgment Reference: 1. Grass, wood, bamboo chip, fiber, wire, plastic, sand, and other foreign objects. 2. Small veins detached from the shaft. 3. Broken shafts. 4. Wax covering separated from the bottom of immature feather. 5. Fragmented fibers, epidermis, shafts. 6. Left marrow from broken or detached shafts.
