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.
Placing the annealed copper in Sparex cleans most, if not all of the fire scale from the surface of the metal.
We use Sparex as a cleaning solution to tkae the fire scale off the metal.