anneal
uh-NEEL
/əˈniːl/
To heat metal or glass and allow it to cool slowly in order to remove internal stresses, soften it, and increase ductility.
Annealing intentionally softens metal that has become hard and brittle from cold working (hammering or bending), resetting its crystalline structure.
The story behind the word. Anneal stems from Old English 'anælan,' meaning to burn, kindle, or set on fire. In medieval times, glassmakers and metal artisans used it for the process of setting items in hot kilns to bake out internal strain.
Word relationships
- soften: Soften is general, while anneal refers to a specific thermal cycle of heating and slow cooling to alter crystalline stress.
- quench: Quench cools metal rapidly to harden it, whereas anneal cools metal slowly to soften it.
Commonly confused with
- temper: Anneal cools slowly to make metal maximally soft/ductile; temper reheats quenched metal to balance hardness with toughness.
Word family
- annealed (adjective): Heat-treated for softness and stress relief
- annealing (noun): The process of heating and slow cooling
Collocations
- anneal metal
- annealing oven
- fully annealed
Example sentences
- "After repeatedly hammering the copper bowl, the smith had to anneal it in the forge to make it soft enough to shape further." Metallurgy
- "The handcrafted glass vase was placed in an annealing oven to cool slowly over twelve hours so it wouldn't shatter under thermal stress." Glassblowing
Memory hook
ANNEAL = KNEEL: make the hard metal 'kneel down' and soften under heat. Heat up, cool slow, stay soft.
When not to use
Do not confuse with quenching (rapid cooling to harden) or tempering (mild reheating after hardening).
Fun facts
- If glass is not annealed after blowing, microscopic internal tension will remain trapped inside, causing the piece to spontaneously explode days or months later if bumped slightly.
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