Related Clues:

• Surface matter
• Pond problem
• Wine settlings
• Soap ___ (shower buildup)
• Foundry refuse
• Bottoms of wine barrels
• Bathtub residue
• Volcanic dross
• Dirty film
• The most worthless part
• Metallic waste
• Bottom-of-the-bottle stuff
• Foundry waste
• Furnace waste
• Birdbath gunk