In case wire also referred as wire side and top side. The side which is in contact with the paper machine wire during manufacturing is called the wire side. The other side is top side. Before a thin layer of fibers deposit on machine wire, fines and fillers drain out hence wire side has less fines and fillers compared to top side. Certain properties such as smoothness, texture and ink absorbency differ between wire and felt side and it is customary to measure these properties on both sides. This difference of properties on two sides of paper is known as two-sidedness. Highly filled or loaded or paper made from short fiber pulp will show higher two-sidedness.
In case of paper to be printed on one side only, best results are obtained by printing on felt side. Postage stamps are printed on wire side and then gummed on felt side, where the smoothness is helpful for attaining an even application.
Wire side and top side described above are in reference to single ply paper. In case of multi-ply paper/board, every ply will have wire side and top side. The top side of top most layer will be top side and wire side of bottom most layer is wire side of multi-ply board. Different type of fibers, fillers and chemicals are used in different layers for techno-economical reasons.industrial & scientific
The standards procedure is described in TAPPI T 455
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