HP is underlining its excellent black and white printing capability with renewed claims regarding resistance to fading.
Dr. Miller was able to provide a very lucid background to the different types of photo paper that are in common use today and pinpoint their strengths and weaknesses.
He was particularly confident about HP photo paper's resistance to gas fading, though admitted that as HP uses dye-based inks for photo printing like much of the competition, exposure to UV light was just as much a threat as with other dye-based prints.
Above is a scan of a pair of prints Miller provided that had been aged at an accelerated rate by HP's lab. The print on the left is an HP ink jet print and the one on the right is a conventional silver halide colour print. The visible fading in the conventional print is mainly due to gas fading caused by ozone in the air and humid atmospheric conditions. The estimated age factor for this example is quoted by HP at 34 years.
This diagram explains the differences between papers with porous coatings as used in dye-based photo printers from Epson, Lexmark and Canon. It has the advantage of printing speed, very quick drying and preservation of high gloss finishes. Its disadvantage is the lack of gas attack protection for the printed ink dyes.
With HP's 'swellable' photo paper coatings, once the ink has dried, the coating's gelatine layer forms a barrier to gaseous attack, protecting the printed ink dyes. But there are disadvantages - the ink needs to be applied relatively heavily and drying times are longer compared to porous papers. This is one reason why printing on porous type Canon and Epson papers is not very successful with HP printers; the paper can't take the heavy dose of ink. The swellable coating also doesn't retain glossy shine as well as porous coated papers but Miller says the latest glossy papers from HP are much improved in that area. The robustness of the swellable-type coatings, resistance to physical abrasion and water damage, is also not as good as porous ones, but once again Miller says much improvement has been achieved here as well.