Making It Whiter and Brighter

The graphic arts supply chain is acutely aware of optical brighteners in paper. For the paper manufacturer, it is the blue death spiral. For the printer, it is the color management nightmare. For the print buyer, it is the potential pink slip for not selecting a printer that meets the art directors' expectations.

Just to put us all on the same page, here's a quick definition. Optical brightening agents (OBAs) are chemicals added to papers, fabrics and detergents to enhance appearance under certain lighting conditions. They trick the eye into thinking the medium is brighter and whiter than it really is by shifting invisible ultraviolet light found in daylight and many light sources into visible blue light. In the case of paper, the blue light masks the natural yellow color of paper only as long as the UV-containing light source shines on the paper or print. We then perceive this blueness as whiteness. It's a bit of a scam.

OBAs began to appear in top-of-the-line coated papers several years ago when U.S. papermakers copied their European counterparts' approach to achieving brightness. Papers reach a higher brightness more economically if made with OBAs instead of costly pigments or more highly bleached pulp. They then found their way into uncoated office papers. Unfortunately, uncoated paper production costs increased because the manufacturers shifted the brightness of their papers upward instead of just maintaining the established level more cost-effectively.

Today's landscape is cluttered with papers in all categories that contain increasing amounts of OBAs. Their prevalence impacts the recycled stream, so some packaging grades contain them.

As CTP and the ICC (International Color Consortium) matured, color management of the graphic arts emerged into the world of science. Standards and specifications were promulgated by ISO and U.S. groups aimed at bringing order to print predictability. But OBA-containing paper stymied the measurement technology.

Today's instruments and light booths attempt to simulate a reference lighting condition, such as D50, but do not duplicate the prescribed UV component. This is not critical unless the paper contains OBAs. When it does, measurement of printed color is unpredictable, particularly in the highlight and midtones; and matching proof and press is problematic.

In addition to measurement vagaries, optically brightened papers are photo unstable. The office paper market accepts this instability but not all commercial print buyers are so unforgiving. The yellowed art prints on the wall, the off-hue skin tones or the brochures on the rack that aren't all the same suggest poor printing. Poor quality control at the printer is blamed.

As is often the case, the suppliers to the paper industry are working on our issues. One of these suppliers has just announced an improvement in the optical brightener arena. New Nalco Extra White Brightness Technology enables mills to achieve better and more stable optical properties using a lower level of brighteners, which could minimize the optical degradation in papers over time. In addition, instrument manufacturers, light booth manufacturers and standards bodies are working on solutions for coping with optically brightened paper in calibrations, print and print predictability.

ONLINE: paper channel at graphicartsonline.com/paper