the definitive technical journal for the global gravure ... · features gravurezine tm the...

GravurEzineTM

The Definitive Technical Journal for the Global Gravure Community

YearTwo&StillGrowing

Meeting&ExceedingExpectations:ASpecificationsUpdate

HowManyEsAreThere in a D?

ColorMeasurementonTranslucentMaterials

2007PLGAGlobalScholarshipRecipients

...andmore!

Broughttoyou by

SalmonCreekPublishing

Gravurezine: PluggedintotheWorld

November2007

http://www.laurahatch.com

Features

GravurEzine TMThe Definitive Technical Journal for the Global Gravure Community

GravurEzineTM

GravurEzine is brought to you by GravurExchange, the definitive global resource for up-to-date

gravure information. GravurEzines mission is to deliver to the global

gravure community topnotch technical articles authored by

industry experts, industry updates on an international level, and

overviews of business practices to improve operating efficiencies.

Publisher & Editor-in-ChiefLaura Wayland-Smith [email protected]

Technical EditorsRudy Wiesemann

[email protected]

Dick [email protected]

Volume 2 No. 6GravurEzine

Editorial, Advertising, & Circulation Office

Salmon Creek Publishing7580 Salmon Creek Road

Williamson, NY 14589-9510USA

[email protected]

Contents

Year Two & Still Growing ...............................................................6 Laura Wayland-Smith Hatch, GravurExchangeYear Two has officially begun at GravurExchange and were excited about the challenges and opportunities ahead of us. Weve just gone over the 200,000 hits mark (with 50,000 in the past two months), which means that GravurExchange is continuing to offer the kind of content the gra-vure industry is looking for. Analyzing the statistics yields some interesting results.

PLGA Global Scholarship Winners ..................................................8 Laura Wayland-Smith Hatch, GravurExchange With the fall semester well underway, the Packaging & Label Gravure Association Educational Foundation is pleased to present three of its 2007-2008 scholarship winners.

GIST (Gravure Image Specifications & Tolerances) Update + Meeting & Exceeding Expectations: A Specifications Update ............12 Jean Engelke, Alcan Packaging Food Flexibles North AmericaOn October 4th, 2007, PLGA Global officially announced its leadership role in the development of GIST and kicked off its Technical Conference in Louisville, Kentucky, with a session dedicated to introducing the concept of gravure specifica-tions and the benefits they can deliver to the gravure industry on a global basis. The response from attendees was overwhelmingly positive, with many staying for the final working session to continue the GIST work that was started at the July Summit.

GIST

mailto:[email protected]:[email protected]:[email protected]

phone: 704.844.2434 / 800.756.6474fax: 704.844.2437 / 888.756.6474www.flxon.com

CONTACT US TODAY FOR A FREE CONSULTATIVE EVALUATION OF YOUR DOCTOR BLADE NEEDS

Swedcut Premium Brand Doctor Blades, from concept to shippingcontainer, are designed, engineered and manufactured under a strictISO 9001 Certified Quality Assurance Program in Sweden by SwedevAB (Swedish Development Company). In North America, Swedcutblades are serviced and distributed exclusively by FLXON Inc.

Print efficiency through advanced technology products

WE DELIVER

QUALITYPRINT...

everydayOur customers will acceptnothing but the best qualityand the best service, thatswhy we go the extra mileevery day! Thats why we runSWEDCUT Doctor Blades Rob Layng,

Process ManagerSHOREWOOD PACKAGINGBrockville, Ontario, CANADA

People who know Rob Layng will tellyou hes one of those guys who seemsto never lose his cool. Rob started atBrockville more than 20 years ago, hisfirst real job. He learned gravure print-ing from the ground up and today is incharge of plant wide quality systemsand process improvement. For Rob,the position is a natural. He is highlyorganized and has an uncanny abilityto get to the core of an issue.

Rob will tell youAt Brockville, weface multiple challenges each dayprinting packaging for the food, bever-age and tobacco industries. We printon stocks ranging all the way from11pt. to 19pt. at speeds more than 220meters per minute. Nothing happenseasily. Our success is no mistake!

Rob quickly addsQuality doesnt justhappen. It starts with a top down com-mitment and requires everyones partic-ipation. Quality is truly knowing, con-trolling and monitoring every element ofthe process. For years we suffered withcommon tick marks or drag outs andstreaking in vignettes. That was, untilFlxon introduced us to theirMicrokote blade. The blade solditself! We have enjoyed significantgains in operational efficiency. Ouroperators love them!

The best way to solve print prob-lems is to prevent them from hap-pening in the first place! Thats whywe run Swedcut doctor blades.

Rob may be contacted about the performance of SWEDCUT blades [email protected]

At FLXON Inc our commitment is topresent printers with unique products,technical support and superior servicenecessary to genuinely improve theirprocess, their productivity and their bot-tom line. Other quality products offeredby FLXON include viscosity controlsystems, ink pumps, anti-ghosting cham-bered blade metering systems,100%defect detection systems and vacuum &pin plate mounting systems.

http://www.flxon.comhttp://www.flxon.com

4 www.gravurExchange.com November2007

PLGA Print Quality Awards Competition Entry Form ........................14The Packaging & Label Gravure Association Print Awards program recognizes member printers and con-verters for outstanding achievement in gravure printing. The Awards program, which is open to all PLGA members in good standing, is an opportunity to showcase your gravure printing expertise and gain recogni-tion for your efforts.

How Many Es Are There in a D? ..............................................16 John Seymour, QuadTechProcess control in the pressroom is currently set up around the idea of meeting specific tolerances in terms of density, not in terms of colorimetry. ISO 12647-2 is changing this direction. This standard specifies the range of acceptable color of the four process solids in terms of E, rather then in the traditional D (delta density). As CIELAB makes its way into the pressroom, the question of conversion of tolerances is becoming an issue. The standard does allow for densitometric process control during the press run, but it does not specify equivalent tolerances for density.

Measurement of Color on Translucent Material Viewed by Reflection Part III ........................................................34 Aditya SoleIn the graphic arts industry, color is printed on translucent materials such as polyethylene, cellophane, etc., which are viewed by reflection. Therefore, it is more practical to mea-sure color by reflection-mode geometry with a backing mate-rial.

GravurEzine TMThe Definitive Technical Journal for the Global Gravure Community

Contents

Copyright 2007 Salmon Creek Publishing.

All rights reserved. None of the materials in this publication may be used, reproduced, or transmit-

ted, in whole or in part, in any form or by any means, electronic

or mechanical, including pho-tocopying, recording, or the use of any information storage and

retrieval system without permis-sion in writing from the publisher.

http://www.gravurexchange.com

The Definitive Technical Journal for the Global Gravure Community

IntroducingAmerican Yuncheng Plate Making Inc.

We a packaging e world . . . Leather Cylinders

Woodgrain Cylinders

Packaging Cylinders

In 1992, Yuncheng Plate Making started expansion beyond Shanxi, China, and by 2002 had established more than 40 subsidiaries in Shanghai, Guangzhou,

Qingdao, Dalian, Tianjin, and other Chinese economic and

commercial centers. Today, we maintain an approximate 80%

domestic market share in the gravure market and now operate over 400 of the

most advanced production lines with a sales and services network that covers the globe, giving us the widest-ranging abilities in the world.

Since 1999, we have established branches in Thailand, Mexico, Ukraine, India, Indonesia, Poland, Pakistan, Brazil, Japan, Spain and more. Our American subsidiary will start operation in

early 2008 and several more new companies are planned for North America and Europe.

For more information, contact Irene Qiao (secetary) E-mail: [email protected] tel: (864) 907 4626 (864) 907 1178

Engraved cigarette cylindersFilter-tipping paper print

Laser anti-counterfeiting print cylindersLaser screen cylinders

Engraved flexible print cylinders

http://www.zhiban.com/jtweb


Editorial

Laura Wayland-Smith HatchPublisher & Editor-in-Chief

Year Two has officially begun at Gra-vurExchange and were excited about the challenges and opportunities ahead of us.

Weve just gone over the 200,000 hits mark (with 50,000 in the past two months), which means that GravurExchange is con-tinuing to offer the kind of content the gravure industry is looking for. Analyz-ing the statistics yields some interesting results.

Of no surprise is the growing download rate for GravurEzine. With numbers now approaching an average of 8,000+ down-loads per issue, it is increasingly important on our end to make sure that articles are timely and relevant to a global audience. To that end, I would like to invite all our readers to submit papers for review and eventual publication. Whether its an article on gravure research, new products to advance gravure process efficiencies, or a business-related feature, were interested in sharing it with our global audience. All you need to do is submit it to me at

[email protected]; well review it, and then get back to you with our feed-back and a possible publication date.

And speaking of relevancy, I hope that you have noticed that some of our articles are now being translatedone into Span-ish and several into Portuguesethanks to the help of FLXON, Inc. and Nestor Pires Filho. Our hope is that non-English native speakers will find these translations more easily understood and of real value to their coworkers. Downloadable files can be found at www.gravurexchange.com. Make sure that you check this new library regularly as its content will be growing.

Another interesting find in the Web sta-tistics is the quantity of visitors to our online Gravure Glossary. With hundreds of visitors per month to the various glos-sary pages, it is obvious to us that there is a real need for a common gravure vocabu-lary describing the process and its com-ponents.

Which leads me to announce that the work on GIST (Gravure Image Specifica-tions & Tolerances) has officially begun. A formal working relationship is now in place with PLGA Global (Packaging & Label Gravure Association), and the first workshop was held at their Technical Conference in Louisville, Kentucky, in

Year Two & Still Growing!

GIST

http://www.gravurexchange.commailto:[email protected]:[email protected]

7www.gravurExchange.comNovember2007

early October. The mission of GIST is to document the processfrom beginning to end, design to delivery of productand outline gravure best practices in an easy-to-understand and use manner, enabling the gravure industry to provide consistent and repeatable high-quality printing. If youre interested in getting involved in this work, please contact me at [email protected] and I will be more than glad to explain how the GIST workgroup operates and how you can contribute.

And, a last look at the Web statistics con-firms that the GravurExchange Gravure

Resource Guide continues to serve as a primary gravure directory for the industry. But what is amazing to me is the number of companies not included in its pages. It is an easy & free way to promote your company to the global gravure industry and is one of the best promotional tools we make available to our visitors.

The Resource Guide is a listing of gra-vure printers and suppliers broken down by categories. Listings are free and can be easily accomplished by filling out Gravur-Exchanges online form and hitting the submit button. Within 48 hours, your listing will be posted online, complete

with a company logo and hyperlinks to your companys Web site and e-mail. So, what have you got to lose by not register-ing in the online Resource Guide? Maybe its new customers, so stop procrastinating and register your company in today.

Once again, thanks to each and every one of you for supporting GravurEx-change and GravurEzine. Were working hard to maker sure that were providing the resources and tools that you need, so please dont hesitate to let us know if there is something new that we could be offer-ing. We want to hear from you!

mailto:[email protected]:[email protected]://www.gravurexchange.com/guideform.htmhttp://www.gravurexchange.com/guideform.htmhttp://www.superfinishing.com


Education

PLGA Global Scholarship Winners

My name is Amber Allan and I am currently enrolled in my third year in Western Michigan Universitys Imag-ing/Printing Program. During my time spent at WMU, I have been involved with the Graphic Arts Society. I have been involved with G.A.S. for the past two years, and currently hold the president position. I am also an active member of the Golden Key International Honor Society. In my free time, I enjoy riding my motorcycle, spending time with family and friends, and attending WMU sport-

Amber Allan - Western Michigan University

ing events. After my graduation in April of 2009, I hope to find a job related to pre-press or production.

Scholarship EssayMany people believe that our society is becoming a paperless society and that printing will cease to exist in the near future. People that believe this idea arent familiar with how technology is rapidly changing many aspects and processes of printing. Print is not vanishing; its chang-ing and advancing with technology.

I am currently enrolled in Western Michi-gan Universitys Imaging/Printing pro-gram, which demonstrates that I am interested in all phases of the printing processes, including the gravure print-ing process. Currently this semester I am taking the Rotogravure class and will have the opportunity to be able to work with a gravure press located here on our campus. I am looking forward to working hands-on with the Cerutti press and being able to learn more about the gravure print-ing process including doctor blades, inks, and image carriers.

I also have some experience working in the packaging industry. This past summer I had the opportunity to work at an internship at Schawk, located in Kelloggs headquarters in Battle Creek. I learned a great deal about packaging such as how to build out a package to a new die-line and also how to prepare a package to print to a wide-format printer to be mocked up. Being able to work in this environment at Schawk located in Kelloggs headquar-ters has enticed me to learn more about the packaging industry and all the steps that are involved in order to print the final package.

Working in this professional environ-ment during my internship has also made me realize that the package industry will always exist. After my graduation, I would like to find a career in the packaging indus-try because of its constant demand and its variety (there are numerous types and qualities of packaging). Since there will always be a need for packaging, there will always be a need to print packaging.



Theresa Block - Cal Poly San Luis Obispo

My name is Theresa Block and I am a senior at Cal Poly, San Luis Obispo. In the fall of 2005 I joined Cal Polys Graphic Communication department and instantly fell in love with print, packaging and management. Through my course-work I was able to learn about the many facets of the print industry and fell in love with every one of them. The combination of ink on paper, or any other substrate for that matter, never ceases to peak my inter-est. As soon as I entered this department I began looking for ways to get myself more involved with print. During my junior year I joined the University Graphic Sys-tems team as the Lean manager, where I focused on the elimination of waste and educating the department about Lean and Lean techniques. This year I was selected

as the General Manager of UGS where I am now, for the second year in a row, continuing my experience with manage-ment. This year is a much larger challenge than the year before, but I welcome the challenge and the unique learning experi-ence that will prepare me for my future. Although my concentration is in Printing and Imaging Management, the packag-ing portion of the industry is definitely somewhere I would love to end up upon graduation. More specifically, I would like to particularly be involved with the high quality packaging that only the gravure printing process can achieve. I would like to thank you for this opportunity and for your support in funding my education. Thank you!

Julie M. White - Pittsburg State University

I am just beginning my third year of school at Pittsburg State University. I am currently working towards a dual major in Commercial Graphics and Advertis-ing Communications with a minor in Marketing. I have been very interested in the graphics industry since my senior year in high school when I was enrolled in a Graphic Communications class. I learned a lot about the industry and par-ticipated in several competitions includ-ing a flexography competition in North Carolina. I also competed and won the state of Kansas Skills USA competition for Graphic Communications and then competed at the National level in Kansas City.For the past three summers, I have worked at a company in Kansas City called Span-gler Graphics. I have learned a lot more about the printing process as a whole from Spangler. Just this past summer, I got the

chance to work in the prepress department and I was able to make many of the plates that were then taken out to the different types of presses. I was also able to spend a lot of time in the pressroom and observe the pressmen. I feel like working at Span-gler has shown me a lot more about the printing process from beginning to end. I have learned that there are a lot more things to know about the printing process and I hope to get the chance to learn as much of it as I can.I have found the more that I learn about this industry the more there is to know. It is an always growing and changing field, which I find to be very exciting. I hope to continue learning about the industry even after I graduate. This semester, I am looking forward to joining the College of Technologies Graphic Arts Club, which I hope will teach me more about the graph-ics industry.

mailto:[email protected]


Education

Sri Hemanth Prakhya - Rochester Institute of Technology

Sri Hemanth Prakhya is a graduate stu-dent pursuing a Master of Science in Print Media at the School of Print Media, Rochester Institute of Technology, Roch-ester, New York. He is about to complete his thesis on Visual Agreement between Spot Colors as Printed, as Displayed, and as Proofed. He has done extensive research in PDF and PDF/X workflows primarily focusing on issues such as sup-port for transparency and spot colors.

He has been working as a graduate assis-tant and lab manager for Professor Robert Chung in the Gravure Research Library and the Color Management Systems Lab since Fall 2006. He has also been working as a production expediter for the publica-tion of Test Targets 7.0, an annual publica-tion of RITs School of Print Media. The publication has technical and research articles on various issues in the printing industry written by various faculty and staff members, students, alumni, and guest authors.

Prakhya earned a degree in Bachelor of Technology in Mechanical Production Engineering from Jawaharlal Nehru Tech-nological University, Hyderabad, India. He also worked as a graphic designer for five years extensively in print applications such as commercial, packaging, and label-ing; this experience led him to pursue higher studies in the field of printing.

PLGA Scholarship EssayHow do I match up to the Missions of PLGA GlobalThe mission of the Packaging and Label Gravure Association is to promote the usage of gravure for packaging and label-ing print requirements and to provide

information to its users with the latest technology to improve pressroom effi-ciency and product quality.

In the printing industry, packaging is amongst the most disputed. The color on a package defines the success of the pack-aged product. Repeatability of color is the most important and required aspect in the package printing commerciality. If color is the key for success, then quality is the path of progress. The print quality defines the printing standards of a printed product.

The gravure printing process provides the best quality in printing and it has proven itself in the form of the most used and seen products such as National Geographic Channels book on the world explora-tions, or Hallmark greeting cards, Arm-strong World Industries special printing applications vinyl tile printing. Gra-vure has a great color repeatability factor, which makes it the best printing resource for packaging applications. Color man-agement has a pivotal role to play as the bridge between the input design-color content to the output print content.

Studying and working in color manage-ment has been my forte as it has given me the freedom to explore the print workflow to understand it in a scientific way. If it is color management, then it has to be Pro-fessor Robert Chung, the only primary Gravure academician in School of Print Media at RIT, to teach with utmost dedi-cation and commitment.

I took a Tone and Color Analysis course from Professor Chung, and then later I started working with him on my thesis on Visual Agreement of between Spot

Colors as Specified, Spot colors as dis-played, and Spot Colors as printed. During the course of my working for Prof. Chung, I happened to attend several ses-sions on Gravure and color management for packaging, such as Gravure Day 06 and 07, GraphExpo, Ghent Work Group Packaging Subcommittee meeting, Pack-aging Symposium at RIT, etc. I particu-larly observed that in all of these meetings, the primary points of discussions have been quality of color, support for various color application features in the workflow such as transparency, and other related issues of color.

I have co-authored an article The Six Facets Model of Technology Management Under Conditions of Rapid Change: A Study in the Pre-Media Segment of the Printing Industry. [1] While writing this article, I observed that Premedia required a wide spectrum of skill sets, such as leadership, operations management, and



innovation & technology management, to change with the changing technology in the printing industry.

The current industry concern is the print-ing workflow that has evolved from Post-Script to PDF. While PDF is still evolving with new standards and specifications, the industries that highly depend on Preme-dia and workflow management have been facing a lot of discrepancies that relate to various aspects of their print. Graphic design, color management, and print workflow converge into this one region for the work throughput, which distinctly poses a complicated task. Attaining suc-cess in such a scenario needs profound knowledge of both technical and manage-rial skills.

Having gained a business perspective on the printing industry, Premedia in specific, I have oriented towards various researches in the PDF workflow. I am currently working on a thesis based on a design-to-display-to-print scenario of spot colors that primarily deals with providing a solu-tion to one of the persisting problems in the printing workflows. This problem has been equally existent in all of the printing industries commercial, packaging, and gravure.

I would like to be a part of this effort to make Gravure the best source of package printing and for unbeatable color match-ing efficiencies. With the experiences gained by working for Prof. Chung, and he being the actual Gravure educator, he has really influenced me towards the bet-

terment of the learned knowledge, and to make it much more accessible.

Gravure organizations such as PLGA Global are the greatest inspirations to look forward to obtaining support, and to working on further researches in Gra-vure printing processes. A stride towards contributing my leadership skills to the printing industry will be through making dedicated efforts in implementing the possible solutions to an optimum extent. I

believe that laying the foundation for this most needed change is by putting a firm step forward.

[1] Prakhya, S. H., & Hull, C. E. (2006, October 26). The Six Facets Model of Technology Management Under Condi-tions of Rapid Change: A Study in the Pre-Media Segment of the Printing Indus-try. International Journal of Innovation and Technology Management, 3(4), 407-420

mailto:[email protected]://www.flxon.com


Standards&Specifications

At Alcan Packaging Food Flexibles North America, we place extremely high importance on working with our graphic suppliers and cylinder manufac-turers to exceed our customers expecta-tions. Those expectations are pushing the envelope of the capabilities of both roto and flexo. As you all know, graphic differentiation, print quality, technical execution, and speed to market are critical success factors in the packaging market. Customers count on us to take their ideas and make them reality. And we would be fooling ourselves if we didnt understand that cost is a critical driver behind their success.

More and more of our customers are making their own choices on who pro-vides their graphic solutions. From design house, to separator, to plate or cylinder manufacture, the field of input suppliers is growing. At Alcan Food Flexibles North America, we have over 200 contacts at 64 locations of 31 different graphic suppliers, not to mention the virtually uncountable number of designers, CPC (Consumer Product Company) contacts, locations, and business units.

All of these resources may not have attended one of the many available edu-cational institutions that focus on print-

ing. They may or may not have a design or manufacturing background. In fact, many are color blind. What this means is that they are depending on us, as both printers and an industry, to help them understand the features and benefits of our processes, and provide them with the tools they need to be successful. One of those tools is specifications.

The Flexographic Technical Association recognized this need in 1997 as their rapidly changing technology was nei-ther understood nor utilized to its fullest potential. They developed and published the Premiere Edition of the FIRST (Flex-

GIST (Gravure Image Specifications & Tolerances) Update

GIST Summit

Gravure Professionals from all Print Segments & from Around the World Working Together

On October 4th, 2007, PLGA Global officially announced its leadership role in the development of GIST and kicked off its Technical Conference in Louisville, Kentucky, with a session dedicated to introducing the concept of gravure

specifications and the benefits they can deliver to the gravure industry on a global basis. The response from attendees was overwhelmingly positive, with many staying for the final working session to continue the GIST work that was started at the July Summit. One of the opening session presentations that clearly summarizes the benefits of specifications follows.

Meeting & Exceeding ExpectationsJean Engelke, Print Services LeaderAlcan Packaging Food Flexibles North America



ographic Image Reproduction Specifica-tions and Tolerances) Specifications. The specification encompasses everything from communication, design, and pre-press, to pressroom practices, and quality control requirements. It also covers manu-facturing inputs, quality expectations, and quality control measurement techniques. It is a guidebook and, more importantly, a learning tool that can be used and under-stood by our industry and customers to insure success in the pressroom. Because, at the end of the day, what comes off that press is all that matters. If it does not meet expectations, we have failed to WOW our customers.

The results of the flexo specifications devel-opment have only been positive. They are recognized for industry agreement and collaboration on critical process compo-nents. They have educated customers and suppliers on how the process works and communicated what their expectations are of the design and product attributes to insure success. The flexo market has obvi-ously seen growth in market share. Sup-porting this growth is the communication of standards to manage results. The speci-fications as a reference tool have made it easier to do business with flexo printers by eliminating a lack of process understand-ing.

I know what you are thinking. If we develop industry standards, our custom-ers will hold us to every detail, and your current equipment or process may not be able to meet their expectation. This is a double-edged sword. On one hand it may challenge you to become better, improve your processes, and find out why you are not achieving what the industry agrees is standard. On the other, it will offer the opportunity to exceed the standard and establish and maintain your competitive advantage.

Standards are criteria for excellence. Our own processes are a means to not only accomplish the standards, but also exceed them. Because we all can meet standard does not mean we cannot offer our cus-tomers the step change in performance that comes with organizational experience and commitment to excellence. Standards and specifications are meant to be guide-lines for communication and production practices.

With industry standards we would be providing our customers and their chosen suppliers with a guidebook and a learn-ing tool. It would publicize the features and benefits of gravure and illustrate that we support our customers with the tools they need to be successful. The earlier in the process we communicate our technical abilities, the better, faster, and more cost effective the process will be. Addition-ally, we, as printers and suppliers, can also utilize the specifications to train our own workforce. A publication like this could be used to significantly reduce the learn-ing curve of our own designers, separators, technicians, and pressroom staff. This translates into a reduction in errors due to lack of knowledge, which translates into cost savings for each of us.

Alcan Packaging has very comprehen-sive Flexo and Roto Corporate Graphic Specifications. We have had these in place for many years because we recognize the importance of standard workflow, con-tinuous improvement, and quality. We provide them to our graphic suppliers so they are aware of our expectations when they submit materials and input to our processes. Alcan is committed to having specifications that are in complete align-ment with industry standards. Because of this commitment, it was not difficult for us to adopt and support the FTA guidelines. We know that our customers and graphic

suppliers utilize the FTA FIRST Specifi-cations. They reference them when they are at pre-pro meetings and when talking to our graphics resources. It has provided them with knowledge and understanding of the flexo process. We are now talking the same language which is critical to suc-cess. It also saves time and money by reduc-ing the amount of time spent on project development. When they reference the standards, we are certain that we meet, and in many cases, exceed their require-ments. Establishing industry standards is a process, not a destination. As evidence, the FTA is working on the release of their 4th Edition.

By taking a proactive approach to collabo-rating, documenting, and communicating standards and specifications within our industry, we are demonstrating and chal-lenging our knowledge base. By providing these standards and specifications to our customers, suppliers, and employees, we are executing a method of communica-tion that will affect that graphic differen-tiation, print quality, technical execution, and speed to market our customers are requiring. And, it will result in cost reduc-tion for both customers and the industry by reducing the potential mistakes caused by a difference in expectations. If we focus on standards and procedures, we will not let another technology define our poten-tial or obsolete our capabilities.

In conclusion, I would just like to say that without industry developed and recognized standards we are missing an opportunity to demonstrate our compe-tence and capabilities. New technology, press enhancements, ink developments, and product innovations are leading the industry. If we can increase the number of opportunities to utilize the gravure pro-cess by communicating our standards, the industry will benefit.



2007 PLGA PRINT AWARDS ENTRY FORM

A minimum of 20 samples that were printed in the year 2007 must accompany each entry form. If possible, samples should be of continuous run to show consistency of quality. If label is overprinted include a finished container. If possible include a finished product package/container for use in award photography/publication.

All samples become the property of the Packaging & Label Gravure Association.

Submit entries to:

Packaging & Label Gravure Association (PLGA) 18481 Royal Hammock Blvd

Naples, Florida 34114 Tel: 920-217-6059 Fax: 239-775-1741

e-mail: [email protected]

ALL ENTRIES MUST BE RECEIVED NO LATER THAN DECEMBER 10, 2007

THE ENTRY FEE OF $50.00 MUST ACCOMPANY THIS ENTRY FORM.



PRINT QUALITY AWARD COMPETITION

0 Cartons01 Paperboard-Top-Coated02 Paperboard-Laminated03 Composite Substrate04 Special Structure-Printed

10 Flexible Packaging11 Paper/Paper Lamination12 Film/Film Lamination-Process13 Film/Film Lamination-Line14 Foil/Film Lamination15 Paper/Film Lamination16 Foil/Paper Lamination17 Pouches18 Bags19 Unsupported Foil

40 Coupons, Premiums & Booklets41 Paper42 Film43 Combination Substrates

50 PSA Labels51 Prime Label-Paper52 Prime Label-Film53 No Label Look54 Special Effects/Novelty55 Prime Label with Lamination

60 Medical/Pharmaceutical61 Custom62 Flexible Packaging63 Label64 Functional

70 Security71 Stamps72 Security Printing73 RFID

80 Innovations81 Process82 Materials83 Overall Innovation

90 Specialty 91 Wall Covering92 Floor Covering93 Gift Wrap94 Specialty Converting95 Special Effects/Novelty

100 Technical Achievement101 Specialty Inks102 Specialty Coatings103 Specialty Substrate

The Packaging & Label Gravure Association Print Awards program recognizes member printers and converters for outstanding achievement in gravure printing. The Awards program, which is open to all PLGA members in good standing, is an opportunity to showcase your gravure printing expertise and gain recognition for your efforts.

There are several categories under each product division available in the competition. Eligible companies may submit entries for any category and individual entries may be submitted for more than one category. One winner will be recognized in each of the categories. Awards will be presented during the 2008 PLGA Annual Conference where all winning entries will be displayed. In addition to receiving a PLGA Award, the winner will be announced in press releases to trade journals and will be featured on the PLGA website and newsletter.

The competition is judged by industry professionals with the knowledge and experience required to ensure a fair and equitable outcome. Judges look primarily at the quality of the printing, paying particular attention to registration, color consistency and overall print quality. Consideration is also given to gravure processes and technical excellence. The PLGA reserves the right to reassign entries to other categories if necessary.

All entries must be received no later than December 10, 2007. Individual entries must be submitted separately. Each entry requires a separate entry form and fee. The fee for each entry is $50.00 payable by check or credit card. Late entries will not be submitted to the judges.

Winners will be announced and award plaques presented at the 11th Annual Operational Conference February 27 - 29, 2008 in Miami, Florida

20 Sleeve/Tubes21 Surface Printed22 Reverse Printed23 Composite Substrate24 Heat Shrinkable, less than 12%25 Heat Shrinkable, more than 13%

30 Non PSA Labels/Wraps31 Paper-Top Coated32 Paper-Over Laminated33 Film Surface Printed34 Film Reverse Printed35 Composite Substrate36 In Mold Label-Paper37 In Mold Label-Film38 Heat Transfer Label39 Glue Applied Label



Technology

How Many Es Are There in a D? John Seymour, QuadTech

This work was originally published by TAGA (Technical Association of the Graphic Arts) in the 2007 TAGA Proceedings.

AbstractProcess control in the pressroom is cur-rently set up around the idea of meeting specific tolerances in terms of density, not in terms of colorimetry. ISO 12647-2 is changing this direction. This standard specifies the range of acceptable color of the four process solids in terms of E, rather then in the traditional D (delta density). As CIELAB makes its way into the pressroom, the question of conver-sion of tolerances is becoming an issue. The standard does allow for densitometric process control during the press run, but it does not specify equivalent tolerances for density.

This paper analyzes data from three press tests on web offset and sheet-fed presses, with two different ink formulations and with a total of thirty printing stocks to show that within a press run, running to a density tolerance will assure a colorimet-ric tolerance. The results agree quite well with theoretical calculations.

A further analysis of hardcopy proofs from twenty-one proofing system vendors demonstrates that single-channel density measurements cannot be used to assure a colorimetric match between a proof and a press sheet.

What Do the Standards Have to Say? Color Tolerancing ISO 12647-2 (2004) is a standard that defines a set of requirements for process control of web offset printing. These requirements are set up to assure that a print run produces (among other things) the intended colors. One section of the standard gives targets and tolerances for control patches in terms of colorimet-ric units. It also allows for densitometric tolerances, but only under specific condi-tions.

To understand where densitometry is appropriate and where it is not, we need first to look closely at the places in the

process where color matching is used. ISO 12647-2 has identified three sepa-rate places where color tolerances are important. First, the control patches on the proof must be close to the color values specified in 12647-2. Second, the control patches on the OK sheet must look like the control patches on the proof. Third, the control patches throughout the press run must look like those on the OK sheet.

The relevant colorimetric specifications are found in ISO 12647-2, Section 4.3.2.4, along with Tables 2 and 3. I have created Table 1 to summarize the six specifications from this section.

1. In standards language, the auxiliary verbs should and shall have specific definitions. The word shall connotes an absolute requirement. Compliance to the standard is contingent upon meeting a specification with the word shall in it. The word should is used

http://www.gravurexchange.comhttp://www.taga.org


when it is desirable to meet a tighter specification, but it is realized that such adherence may not always be possible.

2. Since Table 2 refers to CMYK and CMYK only, I assume that primary color solids refers to solid control patches of cyan, magenta, yellow and black. I further assume that process color solids means the same.

3. A digital proof is called out specifically because a closer tolerance is possible for digital proofs than for traditional analog proofs.

Color Tolerancing Through DensitometryTo what extent is density part of the stan-dard? Quoting from ISO 12647-2 (sec-tion 4.3.2.4, Note 4):

Density values can be very valuable for process control during a print run, where the instrument, the ink, and the print substrate remain the same; see ISO 13656. However, in a general situation, density values do not define a colour to the required degree

This paper provides data to support these two statements. The paragraph continues:

Therefore, for the purpose of this section of 12647, reflection density values are only recommended for the determination of tone values.

This sentence seems to be an odd con-clusion. Density values are very valuable during the print run, but are not recom-mended? The rest of the paragraph reads: Following ISO 13656, the production press operator first achieves the correct colour of the solids on the press, then reads the densities with the instrument from the OK print. The densities are then used as aim values for process control during the production run.

This final sentence reads like a recommen-dation to use density during the press run. We can turn to ISO 13656 for clarifica-tion of this paragraph. Section 5.1, excerpt from paragraph 2:

Many of the parameters specified in clause 5, particularly those based on densitometry, are useful for process control, but tell the user little about the appearance of the print. Many of these are appropriate measures for controlling a production run, others for defining the difference between proofs and

prints, and yet others for defining variation within a print

This paragraph, in effect, defines three distinct uses of general reflectance mea-surement devices. Controlling the print run and measuring the variation in a sheet are both encompassed in requirements 3.1 and 3.2 from Table 1. Measuring the color difference between proof and prints is covered under requirement 2 of Table 1. There is a hint that densitometric measurements are appropriate for at least some of these, but this paragraph does not specify which. Section 5.1, excerpt from paragraph 3:

Where colour appearance and matching are paramount requirements, densitometry should not be used unless it is known that the pigments being matched are very simi-lar. Colorimetry is necessary in the general situation.

In other words, density may be appropri-ate if the pigments are similar. I would add that the printing substrate must also be very similar. Certainly the pigments and substrate are similar when we compare patches within a single printed sheet, or when we compare amongst patches from throughout a print run. Based on this, it would appear that density may be appro-priate to meet requirements 3.1 and 3.2.

If the proof was produced on the same stock and the same pigments as the print, then density measurements may also be appropriate to meet requirement 2. This is, however, seldom the case.

Sections 5.2 through 5.7 clarify where colorimetry and densitometry are appropriate.Section 5.2 states that colorimetry is appropriate for the comparison of proof sheet to press sheet.Section 5.4, 5.5, and 5.6 states that the standard print attributes of tone

Req # Patches Sheet Aux. verb1 Aim val Tolerance

1.1 Process color solids Proof Shall Speced values 5 E

1.2 2 & 3 color overprints Proof Should Speced values unspecified

1.3 Primary color Digital Should Speced values

2.5 E

Solids2 proof3

2 Process color Solids OK print Shall Proof 5 E

3.1 Process color Production 68% OK 4 E (CMK)

Solids Sheet Shall Print 5 E (Y)

3.2 Process color Production 68% OK 2 E (CMK)

Solids Sheet Should Print 2.5 E (Y)

Table 1: ISO 12647-2 requirements for the color of solid, single color patches



Technology

value, apparent trap, and doubling and slur are all derived from densito-metric measurements.According to 5.7, densitometry is to be used when measuring variation within one press sheet.Finally, section 5.8 talks about moni-toring the inking during the run. Col-orimetry is preferred and densitom-etry is additional.

Another interpretation of ISO 12647-2 is available in the G7 document (IDEAl-liance, 2006). This is not a standard, it is merely a guideline. It is, however, based on 12647. The following is a quote from Appendix A, Production Press Control:

Begin by running the press to specified ink colorimetric values (see Appendix H) or SIDs. Remember that CIELAB values take priority over density values. Once mak-eready is complete, RELATIVE densitome-try (based on reading a good sheet with your densitometer) remains a valid and efficient basis for run-time press control, and the same density goals can be used to makeready future runsat least for that specific paper/ink/densitometer combination.

General Conversion Problem Ab Initio Look at the Relationship Ab initio in this context means from first principles. Ab initio results are based on theoretical concerns, but are only as good as the initial assumptions. In con-trast, empirical results are based on mea-surements from an experiment, so they are subject to flaws in experimental procedure and measurement error.

In this paper, I take both approaches. Agreement between the two will strengthen the case that this reflects real-ity.

Beers LawBeers law is a law of photometry that has been used to approximate the effect of

increasing the thickness of ink on paper. The law states that the paper-relative den-sity of ink on paper is proportional to the ink film thickness. Refer to the Appendix for the proper name of this law.

Specifically, given the spectrum of a solid patch at nominal ink film thickness S1() P() and the spectrum of paper, P(), the following is the estimate of the spectrum S ()of a solid patch with an ink film thick-ness k times that of the nominal density patch:

(1)

Dividing the reflectance of the ink on paper by the reflectance of the paper gives an approximation of the transmittance of the ink. (Technically, this is an approxi-mation to the transmittance of two layers of the ink, since according to the model, light passes through the ink to the paper and then back through the ink.) Raising this quantity to the power k approximates the effect of a change in ink film. Finally, multiplying by the paper reflectance con-verts back to absolute reflectance.

In order to determine the relationship between changes in colorimetric values and densitometric values, I start with a measured spectrum of each of the process inks. Beers law will then be used to pre-dict the spectra of the inks at various ink film thicknesses. For each predicted spec-tra, I compute both the CIELAB and the density values. This allows a computation of the rate of change in colorimetric values versus the change in density values.

Limitations The use of Beers law for printing ink ignores the effect of surface reflectance and of the translucency of the ink. The model actually does a rather poor job of estimating density, since the amount of surface reflected light and light reflected from within the ink film are a significant

portion of the light collected from a solid ink patch.

At least six empirical mathematical models have been proposed to provide a better approximation to this relation-ship (Blom 1990, Chou 1991, MacPhee 2002). In addition, the Kubelka-Munk equation (Kang 1997, Gustavson 1997), which is derived from physical properties, has proven to be fairly accurate.

While it is acknowledged that there are many models that are more accurate at predicting the spectrum of an ink with respect to ink film thickness, it is my hope that the simpler Beers law will be suit-able for this discussion. After all, I am not looking for a relationship between ink film thickness and spectrum per se, but rather I am looking to generate plausible spectra with arbitrary thickness.

Beers Law Results Spectra for paper and for each of the four solid process colors were pulled from the TR 001 data set. Beers law was used to predict the spectra of the inks for ink film thickness ranging from 10 percent smaller than nominal to 10 percent larger. Density and CIELAB values were computed from the resulting spectra. Plots of the rela-tionships between density and CIELAB values are shown in Appendix B.

NOTE: I have used Status T density throughout this paper. Colorimetric values were computed using D50 light-ing and the tristimulus functions for the 2 observer. I have no reason to expect that any of the results would be apprecia-bly different using different measurement standards, other than stating that Status E densities of yellow patches are consis-tently higher than Status T, so 1.0 E of color difference between yellow patches will probably be a somewhat larger D for Status E than reported here.



Regression was employed between the density and each of the three colorimet-ric values. The slope of this regression line is the rate of change in L*, a*, or b* with respect to density. The square root of the sum of the squares of these three numbers is the rate of change of E with respect to density. That is to say, a change of 1.0 in density will theoretically give a E of this amount. The reciprocal of this number is the density change that corresponds to 1.0 E. If this final number is multiplied by the appropriate colorimetric tolerance (4 E for cyan, magenta, and black, and 5 E for yellow), one arrives at a tolerance for density (see Table 2).

The density tolerances in the chart above are not that far from the solid ink density tolerances suggested in GRACoL 5.0, which states that one may see a variation in solid ink density of 0.10D.

Lesson one is that there is a theoretical rela-tionship between colorimetric and densi-tometric measurements of solid patches. Based on this theoretical relationship, the colorimetric tolerance in ISO 12647-2 can be converted to a reasonable density tolerance.

Empirical Results Coated StocksSheetfed on Eleven Stocks To verify the theoretical answer, data was taken from a test run performed in 1999 on a sheet-fed press. Solid patches of each of the four process colors were printed at ten different ink film thicknesses. Fifteen different paper stocks were used: eleven coated and four uncoated. The collection of stocks was chosen to cover a range of brightness, fluorescent component, and gloss. Table 3 shows the eleven coated stocks included in the test.

4The fluorescence reported in this column was determined by comparing reflectance with and without a UV filter on the light source. The higher the number, the more the paper fluoresces.

Figure 1 is an example of how the trans-form between densitometric and colori-metric values depends upon the substrate. This concept is developed further in Appendix C. I have shown only the plots of cyan. Graphs for the three inks are not shown because the cyan graph is illustra-tive.

The four uncoated stocks are included in Figure 1 to illustrate that the transform from density to CIELAB values depends upon on whether the paper is coated or uncoated. Four lines are distinct from the rest. The lines all have a sharper downward slope, and their maximum densities are all below 1.0. These four lines are from the four uncoated stocks. Lesson two is that uncoated stocks are significantly different from coated stocks.

For any particular coated stock, the corre-spondence between density and L* value is quite well behaved. The data points relat-ing density and colorimetric values are all smooth curves.

As we go from one stock to the next, how-

Ink Slope L* Slope a* Slope b* E/D D/E Density tolerance

Cyan -17.5 -6.7 -19.7 27.2 0.037 0.15D

Magenta -15.7 19.6 15.9 29.8 0.034 0.13D

Yellow -4.6 4.9 62.9 63.2 0.016 0.08D

Black -27.0 0.1 -0.9 27.0 0.037 .0.15D

Table 2: Results from Beers law computation

Paper name Grade Gloss Fluor.4 L* a* b*

1 Champion proofing paper white 3 68.8 -0.029 88.87 0.21 4.07

2 Consolidated centura dull cover white (grade 1) 2 42.5 0.116 94.86 -0.70 -1.38

3 Consolidated centura dull text white (grade 1) 2 42.1 0.118 92.73 -0.44 -1.93

4 Consolidated fortune gloss cover white 1 83.8 0.156 94.45 -0.10 2.72

5 Consolidated reflections gloss text white (grade 1) 2 35.5 0.146 95.05 -0.85 -2.64

6 DalEl preeminence dull cover white 1 55.2 -0.001 94.67 -1.20 -1.50

7 DalEl preeminence gloss cover white 1 79.0 0.160 94.06 -0.84 -1.07

8 Fraser halopaque offset cream white 2 45.5 0.060 91.44 0.28 6.42

9 Mohawk 50/10 text fluorescent 1 70.0 0.008 95.75 -0.55 -2.16

10 Sappi opus gloss text white 1 66.3 0.061 92.27 -0.62 -2.20

11 Sappi somerset gloss text white 2 32.9 0.136 92.27 -0.62 -2.20

Table 3 Coated stocks in the sheetfed experiment



Technology

ever, there is at least a five point spread in L* values for any particular density.

Lesson three is that direct conversion from density to colorimetry is possible for any particular stock, but that the conversion depends on the stock that is printed on.

Computing Conversions Since the Beers law experiment was done with spectra from coated stock, I look first at data strictly from the 11 coated stocks.

For each of the four process inks on each of the 11 coated stocks, I computed the density and the L*a*b* values of each of the ten patches. Regression was used to fit a parabola to this data (e.g. the a* values versus density of magenta ink, as measured on paper 7). I computed the derivative of these parabolas at the same density as had been used in the Beers law experiment. For each combination of colorimetric value and paper, I thus had eleven slopes. I computed the average and the standard deviation of these eleven slopes, recorded as x in Table 4. The results from the Beers law calculations are shown in this table for comparison.

The standard deviations of the slopes are fairly small compared to the magnitude of the slopes, being all less than 2.0 out of a range of up to 60. In other words, while the relationship between density and L*a*b* values depends upon the paper, the relationship between the changes in the two is fairly independent of paper, at least within the class of coated stocks.

Lesson four is that the conversion between densitometric and colorimetric tolerances for coated stocks is pretty much the same for all stocks.

Figure 1: L*, a*, and b* value of cyan ink versus density on fifteen stocks



It is seen that the density tolerances derived from the empirical test and from the previous ab initio test are nearly iden-tical. Lesson five is that, for coated stocks, Beers law is adequate to predict the con-version between E and D.

Web Offset Results A web offset test was recently run on 16 different stocks, all of which were coated. Table 5 is a list of the 16 stocks in this test. The stocks are almost all different from the stocks of the sheet-fed test. The press

and press crews were different. The inks used were from a different manufacturer.

There are a number of caveats about this data set. While this is the only web offset data that I have with multiple stocks, the press conditions were not quite as tightly controlled as one would like. (The test was run for other purposes.)

A second significant limitation is that each sheet was run at only a single ink key setting I had to rely on natural varia-tion across the sheet to get a sampling of densities. Fortunately, the sheet had solid patches of each of the inks printed in five places scattered around the sheet. Still, the relatively small amount of variation means the calculations are more susceptible to the normal measurement noise.

Another source of variation is that the five patches selected for measurement did not all have the same image printed on the obverse side. Although the measurements were all made with black backing, there is a potential for a small amount of variation to be introduced for the 32 pound stocks.

Source Ink Slope L* ( x ) Slope a* ( x )

Slope b* ( x ) E/D D/E Dens. tol.

11 stocks C

-17.5 1.0

-4.4 1.7

-16.4 0.9 24.3 0.041 0.16D

M -15.2 0.7 17.1

1.6 20.8

1.5 30.9 0.032 0.13D

Y -3.6 0.6 7.0 0.4

60.7 1.4 61.2 0.016 0.08D

K -26.4 0.7 0.5 0.5

-4.8 1.5 26.9 0.037 .0.15D

Beers law C -17.5 -6.7 -19.7 27.2 0.037 0.15D

M -15.7 19.6 15.9 29.8 0.034 0.13D

Y -4.6 4.9 62.9 63.2 0.016 0.08D

K -27.0 0.1 -0.9 27.0 0.037 .0.15D

Table 4: Experimental results from 11 coated stocks

Paper Grade Weight L* a* b*

Admiral Gloss 2 60 91.86 0.09 -3.48

Influence 3 60 92.03 -0.11 -2.68

Orion 3 60 91.42 -0.07 -2.49

Somerset 3 60 92.03 0.19 -2.81

Vision Plus 3 60 91.90 -0.04 -2.28

BowBrite 76 4 45 87.84 -0.69 -1.41

DeltaBrite 4 60 91.11 -0.44 -2.21

Escanaba Enamel Plus Gloss

4 45 90.25 -0.35 -1.33

Mission Web Gloss 4 45 91.37 -1.00 -0.18

New Liberty 4 45 89.82 -0.32 -2.48

Polaris Press 4 45 89.65 -0.47 -1.13

Advocate Offset 5 32 85.47 -0.40 0.77

Consolidated 5 32 85.00 -0.46 0.82

ElectraCote 5 32 85.74 -0.61 0.91

Krukote 5 32 85.81 -0.72 1.40

UPM Cote 5 32 84.77 -0.77 0.07

Table 5: Coated stocks in the web offset experiment



Technology

It is expected, then, that there will be sig-nificantly more variation in the results than with the sheetfed experiment, and this was indeed the case. Averaging over 16 stocks has helped, though, and the overall results are very similar to the results of the two previous experiments (see Table 6).

As stated before, the data that went into the test of 16 web offset stocks did not span a large difference in density. To rec-tify this, I look at one further set of web

The numbers track fairly well with each other. While there are individual differ-ences that are statistically significant, the

end result is four sets of densitometric tolerances that differ by no more than 0.01D.

Lesson six is that the conversion between E and D does not depend greatly on whether the press is web offset or sheet-fed, or on the manufacturer of the process inks.

Uncoated Stocks Results The theoretical and the empirical experi-ments were run on the data from the four uncoated stocks listed in Table 7, with the results from the experiment in Table 8.

The results between Beers law and data from the four uncoated stocks concur well, with the exception of the L* and a* values of cyan. The ultimate conversion between E and D is not particularly different between Beers law and actual computed data.

Lesson seven is that Beers law can also be used to predict the conversion between E and D for uncoated stocks.

Why is Cyan Different? It is curious that those two individual values stand out against otherwise excel-lent agreement between empirical and


Slope b* ( x ) E/ D D/E Dens. tol.

16 stocks C -18.4 3.4 -2.9 5.1 -15.4 4.8 25.2 0.040 0.16D

(web offset) M -11.1 3.9 13.7 6.4 21.3 8.4 29.3 0.035 0.14D

Y 2.7 2.7 -2.3 1.8 72.0 4.9 72.2 0.014 0.07D

K -28.5 0.5 -0.6 0.4 -3.0 1.0 28.7 0.036 0.14D

Single stock C -17.5 -5.0 -18.3 25.8 0.039 0.15D

(web offset) M -11.7 17.2 20.1 28.9 0.035 0.14D

Y 0.8 2.6 73.1 73.2 0.014 0.07D

K -25.3 -1.2 -5.1 25.8 0.039 0.15D

11 stocks C -17.5 1.0 -4.4 1.7 -16.4 0.9 24.3 0.041 0.16D

(sheetfed) M -15.2 0.7 17.1 1.6 20.8 1.5 30.9 0.032 0.13D

Y -3.6 0.6 7.0 0.4 60.7 1.4 61.2 0.016 0.08D

K -26.4 0.7 0.5 0.5 -4.8 1.5 26.9 0.037 .0.15D

Beers law C -17.5 -6.7 -19.7 27.2 0.037 0.15D

M -15.7 19.6 15.9 29.8 0.034 0.13D

Y -4.6 4.9 62.9 63.2 0.016 0.08D

K -27.0 0.1 -0.9 27.0 0.037 .0.15D

Table 6 Experimental results from 16 web offset coated stocks

Paper name Grade Gloss Fluor. L* a* b*

12 Sappi strobe dull cover white 4 5.3 0.032 95.75 -0.55 -2.16

13 Unisource pressmaster offset white 4 8.1 0.022 90.03 -0.19 -0.61

14 Unisource star bright opaque white fluorescent 5 8.4 0.254 91.86 -1.34 -5.37

15 Weyerhauser cougar opaque white fluo-rescent (uncoated freesheet)

5 7.6 0.242 92.97 -1.32 -5.94

Table 7: Uncoated stocks in the sheetfed experiment



theoretical results. The solid lines in Figure 2 show three measured spectra of cyan ink on an uncoated stock. The asterisks show spectra computed from the middle of the three spectra using Beers law. The thickness parameter k was adjusted so as to match in the region of 600 to 700 nm where cyan density is measured. It is clear that the Beers law model underestimates the change in reflectance in the region from 400 to 500 nm.

One possible explanation might be that fluorescent whitening agents in the paper have caused the difficulty. The Beers law computations in Table 8 and the graph in Figure 2 were based on paper 14. Paper 14 has the single highest fluorescence of all the sheet-fed stocks.


Slope b* ( x ) E/ D D/E Dens. tol.

4 stocks C -39.3 3.3 9.6 2.9 -25.8 3.7 47.9 0.021 0.08D M -27.1 3.3 35.6 2.1 14.4 11.6 47.0 0.021 0.09D Y -4.6 1.9 4.6 4.4 72.2 5.7 72.5 0.014 0.07D K -37.3 1.9 1.6 1.3 -2.0 3.7 37.4 0.027 0.11D

Beers law C -28.2 -9.2 -24.2 38.3 0.026 0.11D M -28.4 39.4 15.6 51.0 0.020 0.08D Y -3.2 2.9 75.2 75.3 0.013 0.07D K -39.2 -0.1 3.3 39.3 0.025 0.10D

Table 8: Theoretical results from four uncoated stocks

Source Ink Slope L* Slope a* Slope b* E/D D/E Dens. tol.

Empirical 12 C -37.0 6.3 -29.6 47.8 0.021 0.08D

Beers 12 C -28.0 -14.4 -30.9 44.2 0.023 0.09D

Empirical 13 C -38.7 9.8 -28.2 48.9 0.020 0.08D

Beers 13 C -29.5 -13.7 -29. 43.8 0.023 0.09D

Empirical 14 C -40.2 9.1 -23.2 47.3 0.021 0.08D

Beers 14 C -28.2 -9.2 -24.2 38.3 0.026 0.11D

Empirical 15 C -41.2 13.2 -22.0 48.5 0.021 0.08D

Beers 15 C -28.1 -10.1 -25.7 39.4 0.025 0.10D

Table 9: Beers law on stocks 12, 13, 14, and 15

Figure 2 The source of the discrepancy for cyan



Technology

To rule out this possibility, Table 9 com-pares empirical and theoretical results on each of the four uncoated stocks.

Fluorescence is not the issue, since all four stocks show the same effect. The reason for the failure of Beers law to estimate spectra of cyan ink on uncoated stock is unknown.

Danny Rich (Sun Chemical) pointed out that inks will sink into an uncoated stock more so than into a coated stock. This may be the reason why the Beers law model is less accurate for uncoated stocks. The Kubelka-Munk model, which takes opac-ity into account, may work better. This does not explain why there was no appar-ent problem with the other inks. Yellow and black may have had good results just

because the spectra of these inks are less interesting. Magenta is a puzzlement.

Proof to Press Sheet ComparisonThe results from the previous section demonstrate that densitometric tolerances can be an effective proxy for colorimetric tolerances when comparing the ok sheet (from the press run) to the subsequent press sheets. Are densitometric tolerances equally effective for colorimetrically com-paring a press sheet to the proof ? The con-ventional wisdom says no. The 2006 IPA proofing roundup (Sharma et. Al, 2006a, 2006b, and 2006c) provides us with a data set to put this to the test.

The data set consists of spectral measure-ments made on proof sheets printed on twenty-one proofing systems from eleven

different vendors. There are also spectral measurements from the press sheets that the vendors were requested to match.

If we can use density measurements to compare a proof to a press sheet, then we should see that matching the density of the press sheet and proof sheet will guarantee that the E values are very small. All we need to do is compute E values between the solid patches on the press sheets and the solid patches on the corresponding proof sheets.

There is however, a small catch. The solid patches on the two sheets do not neces-sarily match either colorimetrically or densitometrically. Fortunately, we have demonstrated that the Beers law can be used to estimate the spectrum of a solid

Proofing system Paper E Cyan E Magenta E Yellow E Black E Worst E

System 01 1.70 2.85 0.70 2.03 0.40 2.85

System 04 0.44 4.26 2.33 0.76 4.29 4.29

System 07 0.41 4.46 1.77 2.75 0.34 4.46

System 09 0.31 2.79 3.16 2.30 0.36 3.16

System 14 0.19 1.55 1.99 1.65 0.22 1.99

System 15 0.53 0.78 6.05 1.11 0.91 6.05

System 17 0.26 1.38 0.24 3.43 0.79 3.43

System 18 1.49 0.63 4.75 2.42 0.29 4.75

System 19 1.96 0.93 1.65 1.22 0.87 1.96

System 23 0.70 0.31 6.98 1.31 0.29 6.98

System 24 0.16 1.22 4.88 2.68 0.69 4.88

System 31 2.10 0.99 1.98 0.98 0.99 2.10

System 33 2.95 2.03 2.95 4.87 2.30 4.87

System 35 1.05 0.74 5.17 1.94 0.55 5.17

System 36 0.40 2.20 3.00 1.42 1.01 3.00

System 38 0.26 1.47 1.23 0.96 1.47 1.47

System 43 0.75 1.35 2.67 4.65 0.81 4.65

System 44 1.17 1.96 4.94 1.71 1.14 4.94

System 46 0.72 0.57 4.70 2.04 0.35 4.70

System 47 0.54 0.79 6.17 1.41 0.88 6.17

System 48 0.12 0.34 5.93 2.15 0.27 5.93

Average 0.87 1.65 3.53 2.12 0.94 6.98

Table 10: Results from test of densitometric matching of proof and press sheets



ink on a press sheet at a different ink film thickness. I used this to estimate what the spectrum of the solid on the press sheet would be, if the densities matched. From the estimated spectra, CIELAB values were determined.

Comparison of Absolute Numbers Table 10 shows the results. Surprisingly, the colorimetric differences between the proof and press sheet paper by itself were up to almost 3 E. One would expect that this would cause some problems in trying to match the proof.

If our goal is to establish a match between proof and press sheet to within 5 E, an average measurement error of, for exam-ple, 3.5 E on the magenta is unaccept-able.

Comparison of Paper Relative Measurements In the previous section, it was pointed out that, in some cases, the proof paper and the press stock had a surprisingly large E. Would it improve the results of this experiment to correct for this difference?

In densitometry, there are proponents for the use of paper relative measurements for the purpose of quality control. The paper relative density is computed by simply subtracting the density of the paper from the density of the ink patch. This is math-ematically equivalent to converting the densities of paper and patch to reflec-tances, dividing the patch reflectance by the paper reflectance, and then converting back to density.

It is possible to compute CIELAB mea-surements that are paper relative by the same technique. That does not mean sub-tracting the L*a*b* values of paper. Paper-relative CIELAB values are arrived at by dividing the XYZ values by the XYZ values of the paper. Note that the formula for computing L*a*b* already specified

white object color stimulus (CIE 15.2, section 4.2.2). Paper-relative CIELAB is just using the paper as the specified white object color stimulus.

Are the results better? Unfortunately, no. Some numbers improve, some get worse, but on the whole, there is little difference. If a press sheet matches the paper relative density of a proof sheet, the paper relative colorimetric agreement is not any better than using absolute measurements.

Lesson eight is that density measurements are not useful for comparing proof to press sheet.

Why Doesnt Proof to Press Sheet Comparison Work? Figure 3 shows a comparison of the spec-tra of the solid magenta patch printed by proofing system 23 (dotted magenta line) as compared with the estimated spectra of the solid magenta patch on the press sheet (solid magenta line). The solid magenta for system 23 had the largest color error (see Table 10). The magenta densities of these two patches are equal. The green line shows the Status T filter used to measure Status T magenta density.

As can be readily seen, the spectra of these two inks are significantly different. One

would assume that the different pigments are being used. The difference in pigments is the cause of the metamerism between densitometric and colorimetric measure-ments (Habekost 2006).

This difference in pigments will also cause problems in matching the proof with the press sheet under different illuminants. It will not be possible to match this proof under both D50 and incandescent light-ing.

What about Ink Contamination? An assumption of this whole study is that the inks should not change through the run. Under normal conditions, this will be the case, but there is one situation where the inks may change through the run. This situation is known as backtrap. Backtrap occurs when the ink from an upstream print unit contaminates a downstream print unit. In severe cases, the ink in the yellow ink fountain (which is often the last ink printed) may take on a greenish cast from backtrapped cyan ink.

The colorimetric tolerances in ISO 12647-2 will flag such a problem. Ink con-tamination from backtrapping will cause a change in the hue of the ink, which will show up in the E. This is problem-atic for traditional density measurement,

Figure 3: Comparison of spectrum of magenta inks



Technology

where only a single number is generally recorded.

Hypothetically, the off-channel data could be used to detect contamination. For example, the blue channel of a den-sitometer is used to measure the density of yellow ink. A significant change in the green channel indicates that yellow ink contaminated by magenta, and a signifi-cant change in the red channel indicates that yellow ink has been contaminated by cyan.

In 1957, Preucil defined the calculation of hue error and greyness in order to deal with the unwanted absorbances of the standard printing inks for color separation. These two numbers are calculated directly from density measurements (CGATS 1993). The two quantities are plotted on a circu-lar graph (Yule 1967, page 160 162, and Breede 2006).

A recent TAGA paper (Breede 2006) showed that hue error and greyness are essentially equivalent to CIELAB for measuring three-color gray patches.

In another TAGA paper (Viggiano 1991) Viggiano demonstrated a technique for the conversion of colorimetric data into values that are functionally equivalent to greyness and hue error.

Manfred Breede of Ryerson has reported in a personal communication that ink trap values can be used as an indication of when conditions are such that ink contamina-tion might occur. Trap is computed from densitometric measurements of overprint patches (red, green, and blue). A trap value

that is too low suggests that the tackiness of the first down ink may be inadequate to allow transfer of the second down ink. These are precisely the conditions where the ink might be contaminated due to backtrapping.

From this, it is a reasonable hypothesis that densitometrically derived parameters, such as hue error and greyness, could be used to quantify ink contamination.

There was no discernible ink contamina-tion in any of the data sets presented here, so I have no data to gauge the efficacy of using densitometry to gauge ink contami-nation. This is a topic for future research.

ConclusionsThe one general conclusion for this paper is that densitometry and colorimetry are equivalent in terms of maintaining consis-tent color on press. I also offer the follow-ing eight detailed conclusions:

1. There is a theoretical relationship between colorimetric and densitometric measurements of solid patches. Based on this theoretical relationship, the colorimetric tolerance in ISO 12647-2 can be converted to a reasonable density tolerance.

2. Uncoated stocks are significantly different from coated stocks in terms of conversion of color measurement tolerances.

3. Direct conversion from density to colorimetry is possible for any particular stock (and ink set), but that the conversion depends on the stock that is printed on.

4. The conversion between densitometric and colorimetric tolerances (not actual values, but changes in values) for coated stocks is pretty much the same for all stocks.

5. For coated stocks, Beers law is adequate to predict the conversion between E and D.

6. The conversion between E and D does not depend greatly on whether the press is web offset or sheetfed, or on the manufacturer of the process inks.

7. Beers law can also be used to predict the conversion between E and D for uncoated stocks.

8. Density measurements are not useful for comparing proof to press sheet.

I provide the following conversions from the E tolerances in ISO 12647-2 to den-sitometric tolerances:

E D

(Coated) D

(uncoated)

Cyan 4.0 0.16 0.10

Magenta 4.0 0.14 0.09

Yellow 5.0 0.08 0.07

Black 4.0 0.15 0.11

AcknowledgementsI would like to thank the members of CGATS for their review and comments. Additional comments were provided by John MacPhee and Manfred Breede. Appendix C was inspired by a diagram from Bill Birkett. I appreciate permission from Steve Bonoff to use the IPA data.



Appendix A Who Made Beers Law?Stiglers law of eponymy states that No scientific discovery is named after its origi-nal discoverer. (Stigler 1999)

I have stated that Beers law says that opti-cal density is proportional to ink film thickness. There is some confusion in the literature about the proper name for this law.

The authoritative early text on color and ink (Yule 1967) refers to the additivity rule, that the densities of overlaid inks ideally should be additive. The only men-tion of Beer, Lambert, or Bouger is in the index, which contains the phrase Beers law, and refers the reader to the page that talks of the additivity rule. However, referring to the law of additivity as Beers law is a misnomer.

The first statement that transmission of light through a medium is propor-tional to the thickness of that medium is due to Pierre Bouguer in 1729, when he investigated the loss of light through the atmosphere (Wikipedia, Answers.com [Bouguer]). Johann Heinrich Lambert was unaware of the work of Bouguer and wrote a treatise in 1760 that made him the father of the science of photometry (Photometria sive de mensura et gradibus luminis, colorum et umbrae). This treatise provided a theoretical basis for the rela-tionship between absorption and thick-ness of a medium (Wikipedia, SEDS, and Watson).

The contribution of August Beer did not come until 1852, when he showed that the optical density of a medium is also

proportional to the pigment concentra-tion in the medium.

According to one encyclopedia (Van Nos-trand, 1968), the Bouguer law (AKA the Lambert law of absorption) states that optical density is proportional to the thick-ness of an absorbing substance. Bouger published this law in 1729. The law was again published in 1760 by Lambert, and the law is often attributed to him (p. 229). The entry for Beers law extends the law to state that the optical density is also pro-portional to the concentration of pigment (p. 190).

Wikipedias entry under Beer-Lambert law states that the law that optical density is proportional to thickness and to concen-tration is known by Beers law, Lambert-Beer law, and as Beer-Lambert-Bouger law. This encyclopedia agrees with the dates for Bouger and Lambert, and adds that Beers contribution was in 1852.

A second reference (Menzel, 1960) defines Bouguers law (note the spelling change) as the statement that optical density is proportional to thickness, and Beers law is the statement that optical density is pro-portional to concentration and to thick-ness (p. 419). These two definitions agree with the Scientific Encyclopedia (Van Nostrand, 1968). However, in another section of this encyclopedia (Menzel, p. 662), this second law is referred to as the Lambert-Beer law. According to a third reference (Lapedes, 1978), Beers law states that optical density is propor-tional to pigment concentration alone (p. 86). The law that optical density is proportional to thickness is referred to as the Bouguer-Lambert-Beer law, the Beer-

Lambert-Bouger law, and the Beer-Lam-bert law (p. 106-7). The entry for Lam-bert-Beer law (p. 541) directs the reader to Bouger-Lambert-Beer. The definition for the Bouger-Lambert law (also known as Lamberts law) is a differently worded statement of the same law.

A fourth reference (Gray, 1963) says that Beers law is the statement that optical density is proportional to concentra-tion (page 6-2), and that Lamberts law of absorption is the statement that opti-cal density is proportional to thickness (page 6-5). Forty pages later (page 6-45), this book gives the same definition for the Lambert-Beer-Bouger law.

A fourth reference (Gray, 1963) says that Beers law is the statement that optical density is proportional to concentra-tion (page 6-2), and that Lamberts law of absorption is the statement that opti-cal density is proportional to thickness (page 6-5). Forty pages later (page 6-45), this book gives the same definition for the Lambert-Beer-Bouger law.

Confused?

Since there seems to be little agreement about who is responsible for which law, I have chosen to refer to the statement that optical densities of filters add as Beers law. My decision is not based on historical evi-dence, but on the gedanken I introduced in a paper given at IS&T (Seymour, 1995). In this, I demonstrated the law by using a varying number of mugs filled with beer. My hope is that my further corruption of already corrupt historical fact will help remember the law!



Technology

Appendix B Graphs from Theoretical Results



Black

-4

-2

0

2

4

6

1.40 1.45 1.50 1.55 1.60 1.65 1.70Density

b*



Technology

Appendix C General conversion problem In this appendix, I describe diagrammati-cally the problems with conversion of tol-erances.

In the hypothetical diagram C.1, we are comparing the OK sheet against subse-quent press sheets. We have previously established that the OK sheet has proper CIELAB values when the density is, say, 1.34. As we adjust the ink level, the CIELAB values will follow the trajectory in CIELAB space. Holding the density between 1.27 and 1.39 will ensure that the CIELAB value is within the tolerance circle.

Figure C.2 demonstrates that, when matching a press sheet to the proof, it may not be possible to exactly reach the target CIELAB value. If all is well, it will be pos-sible to get within the tolerance circle. From this drawing, it would appear that a range of density from 1.33 to 1.40 will yield CIELAB values within the toler-ance.

In figure C.3, it is shown that ink on two different stocks may have different ranges of density that yield CIELAB values within the tolerance. The density range for this hypothetical second stock is per-haps from 1.27 to 1.39.

This is an issue! We cant define an accept-able range for density that is independent of the stock.

Birkett has defined a preferable measure called the colorimetric tone value. The ISO-CTV lines in the figure C.4 are the lines that have constant CTV. The benefit of CTV is that the relationship between CTV and CIELAB values is independent of what paper you are dealing with. One benefit is that the range does not shift back and forth with stock. A second benefit is that it is a necessary, but not sufficient, condition that the CTV be in a certain range in order to be within the tolerance circle.

Figure C.1: CIELAB trajectory of ideal ink on press sheet

Figure C.2: CIELAB trajectory of realistic ink on press sheet

Figure C.3: CIELAB trajectory of ink on two different stocks

Figure C.4: Comparison of CTV to density



Students for the Exploration and Devel-opment of Space Web sitehttp://www.seds.org/~spider/spider/Misc/lambert.htmlW.P. Watson Antiquarian Books Web siteh t t p : / / w w w . p o l y b i b l i o . c o m /watbooks/2823.html

About the Author:John Seymour is an applied mathemati-cian and works for QuadTech, where he has been doing research in printing, color theory, and imaging for the past 15 years.

John was instrumental in the develop-ment of QuadTechs CCS (Color Control System). John currently holds ten patents, has authored nine technical papers, and is a member of CGATS subcommittees 3 and 4 (metrology and process con-trol) and TC 130. Prior to working with QuadTech, John worked in medical image processing, wrote software for alignment of digital imagery from weather satellites, worked on a team that designed an elec-tron microscope and an accompanying image processing system, and wrote soft-ware for spectroscopy. He holds bachelors degrees in mathematics and in computer science from the University of Wisconsin-Madison.

Selected Bibliography Blom, B. E., T. J. ConnerOptical density and ink film thickness; a comparison of models, TAGA Proceed-ings, 1990Breede, Manfred HTesting the Validity of Measuring Gray Balance with the GATF Color Circle, Grayness and Hue Error Values, TAGA 2006CGATS.4-1993Graphic arts reflection densitometry measurements Terminology, equations, image elements and procedures, Graphic Technology, 1993Chou, Shem, Norman HarbinRelationship between ink mileage and ink transfer, TAGA Proceedings, 1991CIE 15.2Colorimetry, 2nd EditionGray, Dwight E., editorAmerican Institute of Physics Handbook, second edition, (McGraw-Hill), 1963Gustavson, StephanDot Gain in Color Halftones, PhD Thesis, Linkping University, 1997Habekost, MartinThe effect of colorants in proofing sys-tems in comparison to standard four color process inks, TAGA Proceedings, 2006IDEAllianceCalibrating, Proofing and Printed by the G7TM Method, Version 6, August 2006ISO 12647-2:2004(E)Process control for the production of half-tone colour separations, proof and production prints Part 2: Offset litho-graphic processes, Graphic technology, 2004ISO 13656:2000(E)Application of reflection densitometry and colorimetry to process control or evaluation of prints and proofs, Graphic technology, 2000Kang, Henry RColor Technology for Electronic Imag-ing Devices, SPIE, 1997Lapedes, Daniel N, editor

McGraw-Hill Dictionary of Mathemat-ics and Physics, (McGraw-Hill), 1978MacPhee, John, and John LindInsight into the relationship between print density and ink film thickness, TAGA Proceedings, 2002Menzel, Donald, editorFundamental Formulas of Physics, (Dover Publications), 1960Seymour, JohnThe why and the how of video-based on-line densitometry, IS&Ts Fourth Tech-nical Symposium on Prepress, Proofing and Printing, 1995Sharma. Abhay, Tom Collins, Ray Chey-dleur, Steve Smiley2006a IPA Proofing RoundUP Results, IPA 2006b IPA Proofing RoundUP Webinar, IPASharma. Abhay, Tom Collins, Ray Chey-dleur, Steve Smiley, Florian Suessel2006c Visual and Colorimetric press to proof matching using the new GRACoL reference printing condition, TAGA Jour-nal, Vol 3Stigler, Stephen M.Statistics on the Table, Harvard Univer-sity Press, 1999Van Nostrands Scientific EncyclopediaFourth Edition, (D. Van Nostrand Inc.), 1968Viggiano, J A Stephen, and Wang, C Jef-freyA Suggested Method for Computing Colorimetric Densities, 1991, TAGA Proceedings, p 196 - 215Yule, J.A.C.Principles of Color Reproduction, ( John Wiley and Sons), 1967

LinksBeers law, Wikipedia entryhttp://en.wikipedia.org/wiki/Beer%27s_law#HistoryBouguer, Pierre, Answers.com entryhttp://www.answers.com/topic/pierre-bouguer

mailto:[email protected]://www.seds.org/~spider/spider/Misc/lambert.htmlhttp://www.seds.org/~spider/spider/Misc/lambert.htmlhttp://www.polybiblio.com/watbooks/2823.htmlhttp://www.polybiblio.com/watbooks/2823.htmlhttp://en.wikipedia.org/wiki/Beer%27s_law#Historyhttp://en.wikipedia.org/wiki/Beer%27s_law#Historyhttp://www.answers.com/topic/pierre-bouguerhttp://www.answers.com/topic/pierre-bouguer

Visit GravurExchanges Web Shop at www.gravurexchange.com/store

& order your ARS Scope today!

Benton Graphics ARS Scope The answer to many common print problems

Benton Graphics has developed a portable tool for measuring the contact angles of used doctor blades. This device takes into account the deflec-tion of the blade for a more precise measure-ment. In Gravure, the lower the contact angle, the higher the loading pressure that is necessary to wipe clean.

It is a must for every printing department and is a great training tool for new press operators. Presses running improper contact angles can waste thousands of dollars press time alone, not to mention; wasted ink and substrate, excessive blade wear, and the potential damage to the rolls. Benchmark your process when things are run-ning well, or if you currently have blade issues use this tool to help solve them.

This device will tell you:Ifthebladesweresetparalleltotheroll

and everything was lined up properly.Ifyouarerunningintheoptimumrange

for the process.

Includes: microscopic system, custom carrying case (additional cost) reliable LED light source, instructions on how to examine a used blade, and tips on what you should expect to see along with the recommended contact angles for the various processes.

Did you know that many common print problems are attributed to improper contact or running angles of the doctor blades?

http://www.gravurexchange.com/store


theplacetobelisted,whetheryoureagravureprinter,printbuyer,supplier,consultant, oreducator.

7580 Salmon Creek Road, Williamson, NY 14589-9510Tel: 315.589.8879 E-mail: [email protected]

To celebrate the launching

the definitive technical journal for the global gravure ... · features gravurezine tm the...

Documents