The present invention relates to techniques for producing a sealing seam which air-tightly joins together two film sides, in particular two film sides of a film in the formation of a film tube (3), comprising the following steps: · carrying out a pre-sealing process, wherein at least one of the two film sides is heated in a pre-sealing process and wherein, in the heated state of the at least one film side, both film sides are brought into contact with one another, wherein a pre-sealing seam (32) is formed which joins the two film sides together; · carrying out a final sealing process, wherein the pre-sealing seam (32) is supplied at a transport speed to a pressing means (52), wherein, in terms of the process, the pressing means (52) is arranged downstream of the pre-sealing process, in particular as close as structurally possible, and wherein the pressing means (52) applies force to at least one of the two film sides along the pre-sealing seam (32) substantially perpendicularly to the transport direction (25), as a result of which the pre-sealing seam (32) is made into a final sealing seam (54) which is substantially impermeable to air.