Reclosing septum cap for medical sample transport and processing

A method for piercing a septum comprising:

• obtaining a vessel with a pierceable cap thereon, the cap comprising:
• a shell,
• an access port in the shell adapted to allow passage of at least part of a transfer device through the access port;
• the septum seal comprising a collar and a plurality of half-domed indentations extending from a perimeter of the septum toward the center thereof, wherein the indentations extend inwardly and downwardly toward a substantially planar septum floor, the septum floor having a thickness, wherein the shell is adapted to receive the septum seal and wherein the substantially planar septum floor has a slitted portion that extends only partially through the thickness of the septum floor;
• positioning a pipette tip over the septum seal;
• advancing the pipette tip into contact with the septum floor;
• further advancing the pipette tip through the septum floor such that the pipette tip advances through an unslitted portion in the septum floor thickness initially and then further advances through the slitted portion.