You are thinking of dross. I just used it in a crossword.
Dross - solid metal scum or debris floating on molten metal
Dross is a term used to describe impurities or scum that float on the surface of molten metal.
Metal ions in water can react with soap to form insoluble salts, known as soap scum. This can lead to reduced soap efficacy and result in soap scum buildup on surfaces.
Scum - calcium and other metal salts of fatty acids
Shower faucets are typically made out of linoleum metal. They use this kind of metal because it is resistant to all sorts of soap scum and will not block water flow.
The metal bearing ore needs to be crushed, and then heated in a furnace until the metal grains melt and collect together. The slag (waste scum) is drawn off, and the liquid metal is run off into ingot moulds.
SCUM Manifesto was created in 1967.
Scum - band - was created in 2004.
N.Y. Scum was created in 1984.
SCUM Manifesto has 21 pages.
The duration of Attention Scum is 1800.0 seconds.
Attention Scum was created in 2001-02.