To Brighten Or Not to Brighten Scientifically Examining the Controversy Over OBA Inkjet Media Additives

InThink the TrenchesInk ByB y rickr a y w williamsO r k , P h .D. To Brighten or Not to Brighten Scientifically examining the controversy over OBA inkjet media additives. Ray Work, Ph.D., heads their inkjet coatings are not white but coating materials result in excellent print Work Associates, a consul- rather cream or tan in color. This color is longevity with little risk of yellowing, due AND FINISHING PRINTING DIGITAL tant firm specializing in frequently referred to as “natural.” Only to the OBAs fading over the life of the inkjet printing technologies, with the addition of OBAs is a truly white print. In addition, they do not interact applications and markets. or bright white media possible. with the pigments in the inkjet inks pro- He worked for more than With exposure to light and heat, over vided by the printer manufacturers. 28 years in research, research management, time the OBAs can lose their ability to business development and business manage- fluoresce and add the blue light to the WHY BRIGHT WHITE? ment with DuPont. Dr. Work holds a Ph.D. reflectance spectrum. The result is that Inkjet inks contain transparent-col- in physical inorganic chemistry from the the media will revert to the original color ored dyestuffs in the form of pigment University of New Orleans. He can be reached of the materials that make up the media particles. They are small and do not scat- via e-mail at [email protected] or and its coatings. It is unlikely that these ter light. They are used to provide “sub- visit his Web site www.workassoc.com. OBAs will turn yellow. When they de- tractive color.” Their ability to provide a compose, they become colorless. Choice wide color gamut and high color satura- ithin the fine art and profes- of the type of OBA and the amount used tion are dependent on the color and re- Wsional photographic communi- along with it’s location in the final print flectivity of the substrate onto which they ties, there has been increasing interest affect the rate at which this occurs. In are printed. The pigments must remain and discussion concerning the pros and our modern inkjet fine art papers and above the reflective layer, and the layer cons of the use of brighteners—better canvases, the OBAs chosen along with must be as white and bright as possible, described as optical brightening agents high-quality paper, canvas substrates and or the resulting print will be limited in or OBAs—in inkjet media for fine art c ONT i NUED reproductions and long-lasting photo prints. Many statements have been made that suggest these additives will cause the prints to have a short life before fading or yellowing. Some have been told that only “OBA-free” media are truly archi- val. Here I intend to offer some scientific information and third-party laboratory data that will shed some light on this sub- ject and put to rest the fear that OBAs are evil and must be avoided. WHAT IS AN OBA? OBAs are organic dyestuffs that ab- sorb ultraviolet light and reemit or re- flect that light in the blue part of the visible spectrum. They have been used for many years at low levels to whiten and brighten paper and canvas. If they are controversial, then why use them, you might ask. The short answer is that if you want a white substrate on which to print, then they must be used. The Concerned industry members should recall that legendary American scenic photographer Ansel Adams ingredients in canvas and papers, and used fiber papers containing OBAs in the 1970s for his photographic prints. SIGN & DIGITAL GRAPHICS • July 2009 • 43 light (affected by whether the image is unprotected, exhibited behind glass or protected with a compatible protective spray), the effect of optical brighteners may decrease at a quicker or slower rate. Category one, no optical brightener, and category two, a minimum of optical brightener, have been third-party tested by Wilhelm Imaging Research Institute DIGITAL PRINTING AND FINISHING PRINTING DIGITAL Inc. in combination with the Vivera inks from Hewlett-Packard. (The report is Henry Wilhelm, posted on the Hahnemühle Web site.) president of Wilhelm Imaging Wilhelm found that over a simulated Research Institute, test period of 200 years no appreciable holds a test target change in the whiteness of the paper was print. Wilhelm has recently has com- detected. Even in the case of the papers pleted new evalua- belonging to category three, the bright tions of the display life of a range of white papers, after testing by the German art papers and can- FOGRA institute remained stable for a vases—both with and without optical test period of between 20 and 50 years brighteners. (see the certificate on the Hahnemühle Web site). They indicate that bright white papers with a whiteness of between 100 percent color gamut and suffer from low color archivability. The rag and alpha cellu- and 110 percent have been requested by saturation. The colors will look “dirty” lose used contain the lowest possible many of their customers. They indicate by comparison because the color of the amount of lignin, so that the whiteness that it is not possible to produce these pa- substrate is added to the colors of the of the base papers will barely alter af- pers without optical brighteners because pigments to give the final visual color. ter hundreds of years. At the request the main components of the paper, alpha of many customers Hahnemühle of- cellulose, only has a natural whiteness of WHERE OBAS ARE USED fers bright white papers, where optical 95 percent (maximum) and cotton linters Let’s start with fine art papers. They brighteners are needed in production. only 90 percent. must contain some OBAs in order to The whiteness of the base materi- To achieve the maximum color satu- provide a white substrate. Those that are als may alter slightly over a period of ration and color gamut from the inks, a truly “OBA free” offer a cream or “natu- between 20 to 200 years. Some users bright white media is required. ral” color, not a truly white surface. If regard this as a “natural patina” of fine the whiteness or brightness of a paper or art prints, while others find this not to OBAS AND CANVAS canvas is greater than 90 percent, there their liking.” Canvas is produced using glued fab- most likely is an OBA present. In paper, The company offers its customers ric of cotton or cotton/polyester blends, OBAs may be in the paper itself, in the three categories of white papers: coated with a white coating called “ges- coating on the paper or both. • Natural white papers without so,” then coated with an inkjet coating, Hahnemühle, a leading manufacturer optical brighteners which may be matte or satin in finish. of digital fine art papers, has been pro- • White papers with a minimum of Canvas manufacturers face the same is- ducing fine papers for 425 years. They brightener (< 0.1 percent) sues of whiteness as paper manufacturers. make a statement on their Web site • Bright white papers with 0.1 to 0.8 To get a white product, some level of OBA (www.hahnemuehle.com) regarding OBAs: percent optical brightener is required. Here the OBA can be added to “Hahnemühle FineArt would like Hahnemühle indicates that they use the gesso and/or the matte or satin ink- to comment on our use of optical the highest quality optical brighteners, jet-coating layer. Some have claimed that brighteners. As a basic principle the which are added directly to the pulp they can produce white canvas without papers included in the Hahnemühle mixture during production. Over the OBAs, but that has not been possible as Digital FineArt Collection have been course of time, these optical brighteners indicated by Hahnemühle in the discus- rated to last for hundreds of years ac- will lose their ability to reflectUV light. sion on paper. Canvas is naturally beige in cording to the ISO Standard 9706 for Depending upon the print’s exposure to color, and if no OBA is added to the gesso 44 • July 2009 • SIGN & DIGITAL GRAPHICS coating, it remains “natural.” Some OBAs • There is no trend in this data that a coating layer, which is free of OBAs, or must be included to reach 95 percent or suggests the presence of OBAs a canvas where the gesso layer under the higher whiteness and maximum color reduces longevity. inkjet coating contains the OBAs. In these saturation and color gamut. • The use of coatings increases the cases, the claim that the product is “OBA display life in the canvas and ink free” is not credible. “OBA free” claims EFFECTS OF COATING systems tested but only slightly. of better longevity have not been sup- Coatings should be designed to be ported, to my knowledge, in independent compatible with the ink and media on BEWARE OF SMOKE AND MIRRORS laboratory data. Because the “OBA free” which they are used. Incompatible coat- I have become concerned in reading papers and canvases in the Wilhelm test ings may crack or yellow over time. The literature describing novel “non-OBA” results do not appear to offer any sig- coatings should be chosen based on the whitening technologies that make prod- nificant advantage in longevity, it appears recommendations of the provider of the ucts whiter and brighter. What concerns that those claims are simply marketing media and not “mixed and matched” me are the claims that these technologies efforts to promote one product over an- without regard to compatibility.

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