Within the twin-belt continuous casting machine, molten metal progressively solidifies on the mold surfaces as it moves through the mold region, with a sump of molten metal present between the solidifying outer surfaces. Belt coatings, texture, and gas layer modifications are used to fine tune the heat transfer rate from the cast metal to the belt. Full thickness solidification can occur as early as 30% of the way through the mold for thin strip, or up to 2 m beyond the mold exit for large bar where exit water spray cooling and roller support are required.