Mark, this is getting interesting. Any idea how these coatings fare on papers such as Ilford Gold Fibre Silk or Canson Baryta Photographique?
I don't think the aqueous-coatings are all that great for photo type inkjet media. The low-viscosity solvent sprays like Print Shield are most appropriate for the photo type surfaces because they create a thin conformal coating, thus leaving the initial media surface texture more intact. The aqueous-based coatings like Eco Print Shield are more appropriate for canvas because traditional decorative finishes used on canvas are generally brushed on and create a fairly thick final coat. The traditional aesthetic of a fully varnished canvas painting is more of the the look artists are going for with these types of overcoats.
Most of my own personal printing is on the papers like Canson Platine Fibre Rag, Hn Photo Rag Baryta, etc. I'm slowly coming to the conclusion that sealing the microporous ink receptor layer with a thin conformal acrylic coating like Print Shield is really important. Yup, its a PITA and by the time one gets finished spraying a large print you will have more money in that final coating than you do in the ink used to make the image. Ouch! Nevertheless, I think microporous inkjet prints really benefit from sealing those pores with a top coating.
Premier implies the protective benefit is largely due to UV blockers in the spray, but I really doubt that. Even with three or four coats applied, the final coating is too thin to filter out much UVA radiation. Normal glazing like ordinary picture frame glass filters out the UVB/UVC rays, so evaluating UVA radiation attenuation is the key this product claim. Try an experiment with Print Shield on an an OBA-rich paper like Epson Exhibition Fiber. Cover half the paper and spray. Then look at the paper under blacklight. If the coating was a highly effective UV blocker, the coated side wouldn't glow under blacklight. But it does...almost as much as the non sprayed side. So, what's going on here? By sealing the pores, the light-induced and ozone-induced oxidation rate of the colorants is being significantly reduced because the surface area-to-volume ratio of the microporous ink receptor coating is being radically altered. In AaI&A tests and those done by WIR, fade resistance can nearly double when Print Shield (also, re-badged as HN Protective Spray, etc) is used. And equally important, the image layer now has much better scratch and abrasion resistance, so it's a win-win for durability despite being a total PITA to use and expensive as well.
Mark
http://www.aardenburg-imaging.com
