In a method for reducing a solid feedstock (110), such as a solid metal compound, feedstock is arranged on upper surfaces of elements (60, 80, 81) in a bipolar cell stack contained within a housing (25). A molten salt electrolyte is circulated through the housing so that it contacts the elements of the bipolar stack and the feedstock. A potential is applied to terminal electrodes (50, 60) of the bipolar stack such that the upper surfaces of the elements become cathodic and the lower surfaces of the elements become anodic. The applied potential is sufficient to cause reduction of the feedstock. The invention also provides an apparatus for implementing the method.