Manual, explication and more. Intro Running a small print shop with several inkjet printers and a variety of papers and other media, one likes to know every detail of the process. That was the main reason to create this set of paper white spectral measurements. I’m not the first to do it and it isn’t the only place on the web where you can get that information but I try to deliver more content than what has been available so far. I like to thank my son Kasper Dinkla for the visualisation of the measurements, for which he applied an existing open source tool; JFreeChart. Manual The application is a Java based tool. On most computer systems today the necessary environment to let it run will be available. If not, download the suitable Java Runtime Environment and install it. The application is in a jar type format which makes it instantly ready for use while the content is sufficiently compressed for download, so no decompression is needed or should be done. When the application is started there will be some spectral plots visible in the main window right away. One is of Barium Sulphate BaSO4, another Titanium DiOxyde TiO2. In this case used to give some reference for the other measurements to known ‘ideal but existing’ white surfaces. Both components are used as whitening agents in paper coatings. Another spectral plot represents an Optical Brightening Agent, OBA or sometimes called Fluorescent Whitening Agent or Fluorescent Brightening Agent that I prefer. The plots will disappear as soon as other maps or media choices in the maps are ticked. A CTRL + mouse click on other maps and media choices will keep the default curves and add extra curves. A CTRL+ mouse click on an already selected choice will onlydeselect that choice. A mouse right click if possible will have similar functions as a CTRL + left click. A Shift + mouse click visualises a range of media choices. With the arrow/cursor on a media name, the weight in Grams per Square Meter and the Lab color of the paper’s print side is displayed. Other relevant paper properties will be added there later on. A right click on the curves window will give some menu choices for display changes like zooming in and out with different aspect ratios or fixed, save curve visualisations as png images, copy and print facility, etc. Dutch language but it will explain itself. Selecting parts of the curve on the window itself is possible too Purpose While it may have been curiosity that fueled my desire to create this information tool, there could be hidden benefits for its users. For the print shops that are interested in the archival qualities of the paper white, the curves will show whether there are Fluorescent Brightening Agents (FBA) used in the paper and where in its structure; coating or base. Fluorescence can create color inconstancy under different lights. The effect often incorrectly called “Metamerism”. There can be more causes for that effect though. In absence of FBAs, the total reflection and the straightness of the curves tell something about the quality of the normal whiteners used in the inkjet coating and of the paper base reflectance quality. For the book producers the three curves of each paper tell something about the papers opacity- transparency, based on the GSM weight or other properties that influence opacity. The two curves of measurements on black board also tell something about reflectance differences of dual sided papers. The three curves per paper are a good indicator whether papers with different names and from different suppliers may come from the same source. If so that could help on applying suitable ICC print profiles for papers that do not have a profile available, make a selection of a set of matching white papers easier and last but not least gives an advantage in the purchase of the ‘same’ paper from different suppliers. Spectral measurements do not tell all about the paper and its coating but they shouldn’t be underestimated either. Basics For the spectral measurements a new X-Rite Eye One Basic is used, in this case the version that doesn’t have a UV cut filter as I was interested in the fluorescence behaviour of the papers. The software used is X-Rite (Gretag Macbeth) Eye One Share. Three spectral measurements per media were done, one on the print side of the paper with a natural (no FBAs) white museum mounting board underneath the paper to represent a print as mounted (solid line curve), the second a measurement on the same side but the paper resting on a black plastic board (dashed line curve), the third measurement on the backside of the paper and the paper resting on a black plastic board (stipple line curve). The Lab value is derived from the first measurement. Illumination D50, Observer 2°. In the Miscellaneous map the Pressed PTFE Tile spectral plot was reconstructed from a research article graphic and the three measurements on one Teflon Roll were done by me with the Eye One Basic. The PTFE-Teflon choices are a bit out of context here but another idea still not really explored may bring the relation later on. Interpretation of the spectral plots If we start with the Pressed PTFE Powder (red solid line) we see what comes close to an ideal white reflectance surface. A reflectivity just below 100% over a long range of the spectrum, only a part of that is shown here: 380 to 730 Nm. The opal like structure of Teflon gives it that high reflectance. There are no peaks or valleys in the line so it is an ideal continuous spectral white. The line is slightly inclined so not an absolute neutral white but most likely the best neutral white you will find on this planet. Just a (not visible) bit warmer than absolute neutral with the 99.04 percentage value at 730Nm and 98.37 at 380Nm. The BaSO4 sample (brown solid line, covered by the red line) is slightly warmer. No wonder both are used to calibrate optical instruments on in labs. The Teflon Roll is not visible here, it is the poor man’s equivalent of a Pressed PTFE Powder tile. The green and yellow curves represent respectively Canson Rag Photographique 310 gsm and Moab Entrada Rag Natural 300 gsm dual sided. Two quality matt photo/art papers with a hih reflectivity for that kind of papers. They are almost identical but show some interesting small differences. The dual sided coated Entrada should have identical measurements on the two surfaces with black underneath, it comes close to that if you look at the yellow dash and stipple curve. The Photographique’s green curves separate there slightly more. The Epson Enhanced Matte represented by the blue curves shows a huge difference between printable side and the back of the paper. It doesn’t belong in that class and it shows. Opacity is best checked at the right end of the curves, the wider the gap between the solid and dashed curve (same printable side measured respectively with white museum board and black plastic board underneath) the higher the transparency, the lower the opacity of the paper. In this case the Entrada shows more opacity despite its slightly lower weight, 300 versus 310 gsm. Most likely the extra coating side of the Entrada adds to the opacity. The Epson Enhanced shows a much wider gap which will be partly caused by its lower weight of 190 gsm but could as well be the result of an inferior coating that relies more on FBA content for the print side reflectance than on good quality normal whiteners and a quality paper base. FBA content is very visible in the Epson Enhanced, the UV light, left of 420Nm, is absorbed by the agents so doesn’t show reflectance there and converted to visible light, blue mainly, by the agents it shows in the form of a bulge at the other side of 420 Nm. With only the printable side showing that behaviour (solid and dashed curve) it is clear that the FBA content is in the coating itself, the paper base doesn’t have it. Most papers in the list that contain FBA have it both in paper and coating, in some cases more in the paper than in the coating. There are reasons to expect a better fade resistance of the FBAs when applied in the paper than in the coating but much depends on other qualities too. In general FBAs are not fade resistant and should be avoided for prints that have to last. The Epson Enhanced’s print side is cooler in color than the two other papers but its back warmer and less bright given enough UV light in the illumination of the paper. Another example Three Resin Coated papers, two, like most RC papers, with a heavy FBA content. The yellow Ilford N Galerie Prestige Lustre RC most likely has the brighter printing side due to a higher FBA content in the coating. The green Ilford N Galerie Prestige Smooth Pearl RC shows a high FBA content in its paper base and less in its coating. With the FBA in the paper base contained between the polyethylene (RC) barriers it may last longer, less affected by gas fading. The Epson Proofing White Semimatt RC shows an atypical absence of FBA content for an RC paper, it still has a high white refelction, most likely TiO2 whitening agent. The spectrum plots can help in selecting more durable papers, but real fade and color shifting results of papers are better collected from fade testing. The Aardenburg Imaging & Archives founded by Mark McCormick-Goodhart is the best place to check fading of prints including paper white color shifts. Any serious print shop should become a member of that initiative and get full access to all the data collected. Five sets of measurements of Fibre-Baryta papers, the odd one out is the FujiFilm Museum Baryte. The remaining four; Hahnemühle Photorag Baryta, Lumijet Natural Pearl, HP Baryte Satin, Sihl 4804 Professional Photo Barite have a lot in common. Not to spoil your appetite for SpectrumViz itself, the explanation ends here. More than 700 papers measured already, come back for new additions. Copyright on text, illustrations and measurements: Ernst Dinkla Links to relevant subjects On the use of optical brighteners in papers, pros and cons: Differences between brightness and whiteness of paper: Short text on paper opacity: More general information on inkjet paper properties: Inkjet paper data gathered from printing practice:
Any inkjet paper manufacturer or distributor interested in having its papers included in the list, can send samples to me, preferably several A3 or A4 sized sheets per quality. I need more sheets for some print tests later on, the results will be added to the paper properties.