An apparatus for forming laminated sheet glass, comprising: a lower pipe that provides a first glass stream of the core of the laminate; and a first upper pipe that provides a second glass stream onto the first glass stream, the second glass stream forms a first outer clad layer on the inner core of the laminate; wherein a top of the lower pipe and a bottom of the first upper pipe are separated from each other by a first gap on one long side and a second gap on the other long side, a muffle comprising: a first upper portion having a top and at least two long sides; and a second lower portion having an open bottom and at least two long sides, the first and second muffle portions (320, 340) define a chamber occupied by the first upper pipe and the lower pipe respectively; a refractory liner situated between the muffle and the chamber occupied by the first upper pipe and lower pipe; at least one gap seal situated near the gap between the bottom of the first upper portion and the top of the second lower portion of the muffle; at least one heat source within at least one of the first upper portion and the second lower portion of the muffle; and an adjustment system (510, 540) operably adapted to change the relative position of: the first upper portion of the muffle with respect to the second lower portion of the muffle; and the first gap and the second gap between the first upper pipe and the lower pipe; wherein the first upper pipe has a first weir and a second weir, the adjustment system (510, 540) is further operably adapted to change the relative position of the first weir of the first upper pipe with respect to the second weir of the first upper pipe. a lower pipe that provides a first glass stream of the core of the laminate; and a first upper pipe that provides a second glass stream onto the first glass stream, the second glass stream forms a first outer clad layer on the inner core of the laminate; wherein a top of the lower pipe and a bottom of the first upper pipe are separated from each other by a first gap on one long side and a second gap on the other long side, wherein a top of the lower pipe and a bottom of the first upper pipe are separated from each other by a first gap on one long side and a second gap on the other long side, a muffle comprising: a first upper portion having a top and at least two long sides; and a second lower portion having an open bottom and at least two long sides, the first and second muffle portions (320, 340) define a chamber occupied by the first upper pipe and the lower pipe respectively; a first upper portion having a top and at least two long sides; and a second lower portion having an open bottom and at least two long sides, the first and second muffle portions (320, 340) define a chamber occupied by the first upper pipe and the lower pipe respectively; a refractory liner situated between the muffle and the chamber occupied by the first upper pipe and lower pipe; at least one gap seal situated near the gap between the bottom of the first upper portion and the top of the second lower portion of the muffle; at least one heat source within at least one of the first upper portion and the second lower portion of the muffle; and an adjustment system (510, 540) operably adapted to change the relative position of: the first upper portion of the muffle with respect to the second lower portion of the muffle; and the first gap and the second gap between the first upper pipe and the lower pipe; wherein the first upper portion of the muffle with respect to the second lower portion of the muffle; and the first gap and the second gap between the first upper pipe and the lower pipe; wherein the first upper pipe has a first weir and a second weir, the adjustment system (510, 540) is further operably adapted to change the relative position of the first weir of the first upper pipe with respect to the second weir of the first upper pipe.