at least two differently colored components of glass are heated to a molten , viscous state and then combined in a channel shaped forehearth to form a confluent of molten glass in which the starting components remain in discrete domains , delineated by abrupt color transitions at the interfaces between such domains . the confluent flows by gravity to a discharge end of the forehearth , at which the molten glass is fed between a pair of forming rollers which press it into a continuous , elongate sheet of variegated glass . while flowing toward the discharge end of the forehearth , the molten glass is subjected to controlled , limited stirring to break up relatively large domains of homogeneous color into a multitude of smaller randomly dispersed domains characterized by streaks , swirls and waves of individually identifiable colors . a first , coarse stirring operation is performed at a location substantially upstream of the discharge end of the forehearth and consists of reciprocating a stirring paddle in a cross - channel path and thus transverse to the direction of flow of the molten glass . downstream therefrom , gas bubbles are injected into the confluent , from the bottom of the forehearth channel , and these bubbles migrate upwardly through the viscous , molten glass , agitating , stirring and thus further dispersing the individual color domains . finally , a second , fine stirring operation is carried out immediately adjacent the discharge end of the forehearth by manipulating another stirring paddle in a non - synchronous mixing pattern , including up and down and transverse stirring strokes which impart a final , esthetic randomness to the color domains in the glass . adjacent the discharge end of the forehearth , the flow of molten glass is partially obstructed by a shallow weir , over which the glass flows to reach the forming rollers , and behind which a reservoir of molten glass develops to provide a source of supplemental quantities of glass , which is used as needed to compensate for transient shortfalls in the quantity of glass reaching the forming rollers .