Glass manufacturing apparatus and methods

Glass manufacturing apparatus can comprise a forming device comprising a pipe. The pipe can comprise a pipe wall defining a flow passage and a slot extending through the pipe wall. Glass manufacturing apparatus can further comprise a thermal control device defining a thermal control path. A projection of the thermal control path can intersect a footprint circumscribed by an outer periphery of the slot. Methods of manufacturing glass can comprise flowing molten material along a flow direction of the flow passage. Methods can also comprise flowing the molten material through the footprint of the slot. Methods can further comprise operating a thermal control device defining a thermal control path. A projection of the thermal control path can intersect the footprint. Methods can additionally comprise adjusting a temperature of the molten material at a location where the thermal control path intersects the molten material.