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A method of making an easy open end for a container includes steps of providing a can end blank having an end panel and forming the can end blank in a series of forming operations that are performed with specialized and unique tooling. The can end is preferably shaped during the forming operations s

A method of making an easy open end for a container includes steps of providing a can end blank having an end panel and forming the can end blank in a series of forming operations that are performed with specialized and unique tooling. The can end is preferably shaped during the forming operations so that a major portion of the end panel is curved. Specifically, the curvature is preferably such that a top surface of the major portion is generally concave and a bottom surface of the major portion is generally convex. The end panel is also preferably shaped and constructed so that the curved major portion will invert in shape upon the application of a sufficient predetermined pressure differential between the top and bottom surfaces. A method of testing a fill level of a sealed container is performed in reliance on this “cricketing” or “oil canning” effect.

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What is claimed is: 1. A method of testing a fill level of a sealed container having a metallic can end, comprising steps of: filling a container with a product; sealing said container with a can end, said can end comprising an end panel that has a generally curved major portion; and testing a fill

What is claimed is: 1. A method of testing a fill level of a sealed container having a metallic can end, comprising steps of: filling a container with a product; sealing said container with a can end, said can end comprising an end panel that has a generally curved major portion; and testing a fill level of said container, said step of testing being performed in reliance on the shape of said generally curved major portion; wherein said major portion of said end panel is curved so as to comprise a substantially constant radius of curvature within at least one cross-sectional plane taken therethrough; and wherein said major portion of said end panel is substantially circular in shape when viewed in top plan, and wherein a ratio of said substantially constant radius of curvature to a diameter of said major portion is within a range of about 0.05 to about 0.4. 2. A method of testing a fill level of a sealed container according to claim 1, wherein said sealing step comprises sealing said container with a partial vacuum therein, and wherein said can end is constructed so that said generally curved major portion of said end panel is constructed and arranged to facilitate a shape change of said curved major portion when said partial vacuum is diminished by a predetermined pressure rise. 3. A method of testing a fill level of a sealed container according to claim 1, wherein said generally curved major portion includes a generally concave top surface and a generally convex bottom surface. 4. A method of testing a fill level of a sealed container according to claim 1, wherein said major portion comprises at least 75% of a total surface area of said end panel. 5. A method of testing a fill level of a sealed container according to claim 4, wherein said major portion comprises at least 85% of a total surface area of said end panel. 6. A method of testing a fill level of a sealed container according to claim 5, wherein said major portion comprises at least 95% of the total surface area of said end panel. 7. A method of testing a fill level of a sealed container according to claim 1, wherein said end panel further has at least one depression defined therein, said depression being superimposed upon said curvature of said major portion of said end panel. 8. A method of testing a fill level of a sealed container according to claim 1, wherein said major portion of said end panel is substantially spherically curved. 9. A method of testing a fill level of a sealed container according to claim 1, wherein said substantially constant radius of curvature is within a range of about 10 inches to about 75 inches. 10. A method of testing a fill level of a sealed container according to claim 9, wherein said substantially constant radius of curvature is within a range of about 15 inches to about 50 inches. 11. A method of testing a fill level of a sealed container according to claim 10, wherein said substantially constant radius of curvature is within a range of about 20 inches to about 40 inches. 12. A method of testing a fill level of a sealed container according to claim 1, wherein said ratio of said substantially constant radius of curvature to a diameter of said major portion is within a range of about 0.09 to about 0.25. 13. A method of testing a fill level of a sealed container according to claim 12, wherein said ratio of said substantially constant radius of curvature to a diameter of said major portion is within a range of about 0.11 to about 0.20. 14. A method of testing a fill level of a sealed container according to claim 1, wherein said major portion of said end panel is constructed and arranged to facilitate a shape change of said curved major portion when no pressure differential exists between said top surface and said bottom surface.