To reverberate is to heat a charge of ore or metal indirectly by directing the combustion flames against a low, curved furnace roof, which then radiates or reflects the heat down onto the hearth. This keeps the fuel and ash separate from the metal being processed. It is the defining action of a reverberatory furnace, historically used for puddling iron and smelting copper.
Heard on the job
The design allows the heat to reverberate off the firebrick arch and melt the charge without mixing coal ash into the bath.