cores which is interior this means that the moisture barrier includes paper on either side of the moisture barrier the interior moisture barrier may a include film a coating or is impregnated into said tube core a variety of useful materials may be used as the moisture barrier including but not limited to vinyl chloride resin acrylic polyurethane phenolic resin polyester polyolefin foil and combinations thereof adhesives may be included in the layers of the tube core as needed to ensure the integrity of the structure useful adhesives include pressure sensitive adhesives hot melt adhesives reactive adhesives etc the methods of determining the amount of paper that may be excluded from the tube core include observation of the tube core in use after yarn has been wound onto the tube core or testing of the tube core in the absence of wound yarn the testing observation is intended to duplicate conditions to which a yarn package yarn plus the core would be exposed during processing shipping or use this includes exposure to a high temperature and humid environment temperatures may be at or above about 27 u00b0 c including at or above about 30 u00b0 c the humidity may be about greater than about 70 including greater than about 80 or greater than about 90 the humid environment may include humidity of 90 for prolonged periods of time the testing also occurs over time such as approximately seven days typically the core will become saturated with moisture at some time within the seven day period several tube core testing methods are known in the art one such method is described in u s.