Abstract: A method is provided to crimp a sheet having, before crimping, a thickness, a moisture, a composition, and a width, the method including: obtaining one pre-crimping sheet characteristic among the thickness of the sheet, the moisture of the sheet, the composition of the sheet, and the width of the sheet; crimping the sheet to form a plurality of corrugations on the sheet, the crimping including providing a pair of crimping rollers defining a nip therebetween, the nip having a nip size, and inserting the sheet in the nip; evaluating a post-crimping characteristic of the sheet after crimping; and varying the nip size on the basis of the obtained one of the pre-crimping sheet characteristic, and on the basis of the evaluated post-crimping sheet characteristic. An apparatus to crimp a sheet is also provided.