by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : May 2012
Plants & Processes Friend & Foe color Management of Papers containing optical Brightening agents By ray cheydleur Paper manufacturers and ink formulators have brought some excitement to the graphic arts industry with products that contain optical brightening agents (OBAs), the chemicals used to inexpensively whiten and brighten paper stock. But while they are a boon to designers and end users, paper stock and inks containing OBAs are giving headaches to graphic arts companies that are trying to tightly control the reproduction of color along their workflows. Before OBAs were in widespread use, different makes and models of hand-held spectrophotometers had relatively good correlation when they were used throughout a supply chain to monitor and control printing processes. But with today ’s widespread use of colorants, paper stocks, films and foils that contain OBAs, graphic arts companies do not have the same level of confidence that measurements from their instruments agree with the results from suppliers and customers. Help is on the way in the form of International Standard Organization (ISO) 13655, a 34-page standard issued about three years ago that gives highly detailed specifications on how companies can achieve better agreement among spec- trophotometers used in measuring color. ISO 13655 is helping to reduce confusion and improve digital workflow through the use of four conditions for measurement: M0, M1, M2 and M3. Pressroom personnel should be aware of how OBAs can af- fect the final appearance of finished products and know about a simple test to see if OBAs are present in their materials. WHAT YOU CAN’T SEE For less than $20, a graphic arts company can buy a fluorescent black light that will show when substrates or inks contain OBAs, said Gordon Pritchard, a graphic designer in Victoria, British Columbia who writes for The Print Guide blog (www.the-print-guide.blogspot.com), which discusses achiev- ing higher quality in printing. OBAs emit an eye-catching light to a printed piece by absorbing certain wavelengths of invis- ible ultraviolet light, then emitting visible light at the blue end of the spectrum. For instance, “black light” room decorations and posters rely on special paints containing OBAs to emit an eerie glow when they are exposed to ultraviolet light. AGENTS IMPACT APPEARANCE • Brightening agents are added to enhance the bright- ness of the papers and improve the appearance of the printed product, but they can also create a color control nightmare • To ensure consistency, new illumination sources and new substrates require new instrument and mea- surement standards for defining and measuring the relative UV content • New illumination sources, including light-emitting diodes, allow hand-held color measurement instru- ments to measure with well-defined and controlled UV illumination components • Technological advancements, increased distribution of information across different media, and the need to improve the efficiency, productivity and profit- ability have all played a role in the advocation of standards • The new “M ” series of measurement illumination con- ditions allows color management of OBA-enhanced substrates to be further refined to a high degree 52 FLEXO May 2012 www.flexography.org