Apparatus, systems and methods for refining molten glass include a fining chamber having a refractory floor and a sidewall structure that may include a refractory liner, and includes an inlet transition region having increasing width from initial to a final width, and depth decreasing from an initial to final depth. The floor includes a raised curb having width equal to final width of the inlet transition region, curb length less than the length of the inlet transition region, and curb height forming a shallowest depth portion of the fining chamber. The raised curb separates the fining chamber into the inlet transition region and a primary fining region, the primary fining region defined by the refractory floor and sidewall structure. The primary fining region has a constant depth greater than the shallowest depth but less than the depth of the inlet transition region.