What is duplex board?

The grey back is the whole point. Because the reverse is made from recycled fibre rather than bleached pulp, duplex costs noticeably less than a board that is white throughout, and for the very large number of packs where nobody ever looks inside, that saving is free money.

It also sets the limits. If the inside of the carton will be visible — an opened gift box, a display carton, anything with a large window — the grey shows and undercuts an otherwise premium pack. If you need to print on the inside, duplex will do it, but the colour sits on a grey base and looks muted and dirty compared with the same ink on a white one.

Print quality on the coated white side is good. The coating holds a fine screen, colours sit up rather than sinking in, and it accepts every normal finish — lamination, spot UV, foil, embossing. For most retail and pharmaceutical secondary packaging the difference between duplex and a fully white board is invisible on the shelf.

The decision comes down to one question: will anyone see the inside? If yes, look at SBS. If no, duplex is almost always the right answer.