A method of processing a quantity of foam having a first initial thickness along a first axis, a second initial thickness along a second axis, and a third initial thickness along a third axis, the method comprising: applying at least one of a first force in the first axis to compress the quantity of foam to a first compressed thickness in the first axis, a second force in the second axis to compress the quantity of foam to a second compressed thickness in the second axis, and a third force in the third axis to compress the quantity of foam to a third compressed thickness in the third axis; enclosing the compressed quantity of foam in a mold to limit expansion of the foam in at least one of the axes to less than the initial thickness, wherein the step of applying further includes compressing the quantity of foam against an interior surface of the mold; characterized in that fastening the mold with the compressed quantity of foam inside the mold (S151, S305) such that the mold remains in a closed position when the at least one of the first, second, and third forces is removed; removing at least one of the first, second, and third forces from the fastened mold, wherein the fastened mold retains the compressed quantity of foam inside; and with the compressed quantity of foam enclosed in the mold, subjecting the enclosed quantity of foam to at least one of a chemical treatment and a thermal treatment to convert the enclosed quantity of foam to an auxetic foam having at least one of a first treated thickness less than the first initial thickness in the first axis, a second treated thickness less than the second initial thickness in the second axis, and a third treated thickness less than the third initial thickness in the third axis. applying at least one of a first force in the first axis to compress the quantity of foam to a first compressed thickness in the first axis, a second force in the second axis to compress the quantity of foam to a second compressed thickness in the second axis, and a third force in the third axis to compress the quantity of foam to a third compressed thickness in the third axis; enclosing the compressed quantity of foam in a mold to limit expansion of the foam in at least one of the axes to less than the initial thickness, wherein the step of applying further includes compressing the quantity of foam against an interior surface of the mold; characterized in that fastening the mold with the compressed quantity of foam inside the mold (S151, S305) such that the mold remains in a closed position when the at least one of the first, second, and third forces is removed; removing at least one of the first, second, and third forces from the fastened mold, wherein the fastened mold retains the compressed quantity of foam inside; and with the compressed quantity of foam enclosed in the mold, subjecting the enclosed quantity of foam to at least one of a chemical treatment and a thermal treatment to convert the enclosed quantity of foam to an auxetic foam having at least one of a first treated thickness less than the first initial thickness in the first axis, a second treated thickness less than the second initial thickness in the second axis, and a third treated thickness less than the third initial thickness in the third axis.