On a single-wire Fourdrinier, the wire side loses fines and filler through drainage while the top side keeps more, so the faces differ in brightness, smoothness, color and print response. Coating and calendering can add side differences of their own. Twin-wire and gap formers drain both ways and cut two-sidedness, and mills track it as the difference between felt-side and wire-side readings.
Two-sidedness on b-star is almost a full unit, so the duplex copy jobs are going to look mismatched.
When a customer says the sheet is two-sided, ask which property: color, gloss and print density each point to different causes.
Also heard as
- sidedness
Related terms
Wire side
Face of the sheet that lay against the forming wire while the sheet was formed.
Felt side
Face of the sheet that was away from the forming wire, also called the top side.
Fines
Fiber fragments and small particles that pass a fine screen and have an outsized effect on sheet optics.
Fourdrinier
Paper machine design in which stock drains on a single, horizontal moving wire to form the sheet.