The method comprises the following steps: (a) delivering and depositing a first or channel-forming ribbon of molten glass to a surface of a mold assembly having a mold cavity possessing at least one channel-forming groove formed therewithin and a peripheral surface, wherein the channel-forming ribbon overlies the mold cavity and the peripheral surface of the mold assembly; (b) allowing the channel-forming ribbon of molten glass to substantially conform to the contour of the mold cavity resulting in the formation of at least one channel in the ribbon of the molten glass; (c) delivering and depositing a second or sealing ribbon of molten glass to the outer surface of the channel-forming ribbon of molten glass wherein the viscosity of the sealing ribbon is such that the sealing ribbon (i) bridges but does not sag into complete contact with the surfaces of at least one channel of the channel-forming ribbon and (ii) forms a hermetic seal wherever the sealing ribbon contacts the channel-forming ribbon to form a glass article possessing at least one enclosed channel; and, (d) removing the glass article from the mold.
Conformance of the channel-forming molten glass ribbon to the mold cavity in step (b) is achieved by gravity forces, vacuum actuation or by a combination of both.