A long seam gluer for folding a carton blank into cylindrical form and forming a glued seam between the outer surface of a glue flap and a glued area on an overlying side panel includes a magazine for holding a stack of carton blanks, feed mechanism for feeding carton blanks one at a time from the magazine in a predetermined direction with a longitudinal extent of the glue flap in the side panel normal to the predetermined direction, first folding mechanism for folding a first portion of the carton blank including the glue flap into a position overlying a remainder of the carton blank to leave exposed the outer surface of the glue flap, glue applying mechanism for applying a longitudinal body of glue to the glue flap as the glue flap is fed in the predetermined direction with the longitudinal extent of the glue flap normal to the predetermined direction, second folding mechanism for folding a second portion of the carton blank including the side panel into a position overlying a remainder of the carton blank to place the inner surface of the side panel over the body of glue on the glue flap, pressing mechanism to press and hold the side panel against the body of glue on the glue flap until the body of glue has set firmly to secure the glue flap to the side panel to form a flattened cylindrical carton, and a carton opening mechanism adjacent to the pressing mechanism for opening the flattened carton to receive an article therein.