Flat bottomed stand-up microwave corn popping bag

A bag for popping popcorn in a microwave oven comprising, as seen in an upright collapsed position,

• a pair of first and second rectangular face panels each having parallel top and bottom edges defining a top and a bottom of the bag and each face panel having parallel side edges,
• left and right longitudinally extending centrally projecting gusset folds extending between the first and second panels of the bag, the gussets separating the bag into a pair of communicating chambers,
• seals having diagonal edges at both the top and bottom of the bag between the gussets and at least the second face panel, the diagonal edges extending diagonally from the side edges of the second face panel proceeding centrally and toward an adjacent end of the bag,
• the face panels at the bottom of the bag being pinched together and being bonded to one another transversely all the way across to provide a temporary fin at the bottom end of the bag,
• the fin being folded along a transverse fold line parallel to the bottom edge of each face panel and being adhesively bonded to an adjacent outside surface of a face panel to form a transversely extending stay that acts as a stiffening element extending across a rectangular bottom wall of the bag which forms responsive to internal vapor and steam pressure developed during popping of the popcorn in said microwave oven, and
• said stay cooperating with the diagonal bottom seals to assist in maintaining the rectangular bottom wall in a flat condition when the bag inflates under pressure and when the top of the bag is opened for the removal of the popped corn, thereby enabling the bag to stand on said bottom wall when placed on a horizontal surface.