Hi Ben, Martin Weberg wrote:
Hi Ben 2010/4/14 Ben Goren<ben@xxxxxxxxxxxxxxxx>:It just occurred to me. Most papers laced with FWA are coated on one side only. The back side of the paper is uncoated and has no brighteners.Most sheet-fed offset papers that I encountered have equal spectral properties sidewise and yet contain FWA. And yes, most inkjet papers are probably non-equal, but I don't think FWA content is the only factor. There might be non-FWA whitening agents, drying agents and differing paper structure effecting measurements.
Inkjet papers are typically coated on one side. As FWA-free papers are rare these days, the /uncoated/ side should show fluorescence usually I think. At least this is the case with one of these "FWA free" proofing papers (ORIS PearlPROOF™ Super): the ink receiving layer is black under UV light while the backside glows bright blue. This means that this proofing substrate has an "ordinary" paper base and an UV-blocking, FWA-free coating on the print side. And -- as Martin said -- FWA content is surely not the only difference between the front and backside.