Related Clues:

• Coal dust
• Flue accumulation
• Sweep's collection
• Santa's laundry stains
• Chimney sweep's grime
• Stain on Santa's coat, you'd think
• Lampblack source
• Flue deposit
• Schmutz on Santa
• Flue substance
• Stainer of Santa's coat
• Component of Japanese sumi ink
• Pollution portmanteau
• Burnt-coal residue
• Target of a sweep