The term given to paper or board which exhibits different surface characteristics on either side of the sheet. This is due to a different finish imparted by the wire side and the felt side (top side) of the paper machine. Fibres tend to be oriented towards the wire sides of the sheet, while fillers tend towards the top or felt side. In addition, in coloured papers, dyes tend toward the wire side so that side of the sheet may appear to be more coloured than the other. The processing and drying sections of the machine also tend to impart a greater smoothness to the wire side of the paper.