Definition
The solid impurities and oxidized material that float to the surface of molten metal during melting or soldering. Dross is skimmed off and discarded so that only clean metal is used in the work.
Plain English
The scummy waste that rises to the top of melted metal. It is removed before the metal is used so the finished work is not contaminated.
Context Anchor
Seen in aircraft maintenance discussions involving metal heating, welding, brazing, soldering, or casting.
Derivation
From Old English 'dros,' meaning dregs or refuse. The original sense -- 'the worthless part that settles or rises out of something valuable' -- carries directly into the metalworking meaning.
Why Pilots Care
When soldering electrical connections or repairing metal components, dross trapped inside a joint creates a weak, unreliable bond. Mechanics must skim it off before applying the metal to the work.
Intuition Check
Do not think of dross as just discoloration on metal. In this context, it means unwanted waste material or impurities separated from the usable metal.
Example Sentence 1
Before tinning the wire, the technician skimmed the dross from the surface of the molten solder.
Example Sentence 2
Any remaining dross in the weld pool can create weak spots in the propeller blade repair.