Abstract: A container formed from a unitary paperboard blank having a substantially planar inner region, a sidewall region and a rim region formed about the periphery thereof is disclosed. The sidewall region includes a generally annular region flaring upwardly and outwardly from a periphery of the planar inner region and a first frusto-conical region adjoining the annular region with the frusto-conical region sloping outwardly and upwardly from the annular region. The rim region includes an outwardly flaring arcuate annular region adjoining an outer periphery of the first frusto-conical region, and a second frusto-conical region extending substantially tangentially from the arcuate annular region. The second frusto-conical region extends outwardly and downwardly at an angle of about 6.degree. to about 12.degree. and preferably about 6.degree.-10.5.degree. relative to the plane defined by the planar inner region.

Abstract: A method of forming a container from a flat, substantially homogeneous blank of fibrous substrate, comprising the steps of shaping the blank into a formed container having a bottom wall, an up-turned side wall extending from the bottom wall, a rim outwardly extending from the side wall and a lip downwardly curving from the rim and including a plurality of radially-extending, circumferentially-spaced pleats formed in the side wall, rim, and lip, each pleat including at least three layers of the blank; and applying sufficient heat and pressure to the side wall and rim to decrease the thickness thereof to less than that of the blank and to transform each pleat into a substantially integrated fibrous structure in which the constituent layers generally lack individual identity, each structure having a density greater than and a thickness substantially equal to adjacent areas of the side wall and rim.