fire scale

fire scale

[′fīr ‚skāl]
(metallurgy)
Copper oxide remaining below the surface of silver-copper alloys after annealing and pickling.
References in periodicals archive ?
The fire was ranked quite dangerous with number two on the five-point fire scale at 23:17 Moscow time on Friday.
The medallions of pork tenderloin in a creamy blue cheese and mushroom sauce was at the other end of the fire scale. Slender slices of tender meat lay in a Stiltonesque sauce which the bread helped us enjoy to the max.
Flux is applied to the copper liberally to reduce fire scale. The copper is heated to a dull red appearance and may be dipped either into a Sparex solution (a mild synthetic acid recommended for school use) immediately after annealing, or allowed to cool slowly.
We use Sparex as a cleaning solution to tkae the fire scale off the metal.