Creating A Color-Managed Screen-Printing Workflow: A Case Study
This article reveals how implementing standards and color-management procedures affected one graphics screen-printing operation.
Tight process controls and continual analysis of procedures and results are the foundation of a color-managed printing process. This article reveals how implementing standards and color-management procedures affected one graphics screen-printing operation. Despite the number of articles published on color management for screen printing in recent years, the reality—in North America, anyway—is that very few screen printers have implemented a fully color-managed system for printing process-color jobs. Most shops still rely on their press operators and ink technicians to "tweak" the process to produce acceptable work. In this article, we'll take a look at the experiences of a Canadian screen-printing company that recently incorporated a color-management system into its production workflow, focusing on the challenges the shop faced and the benefits it obtained. Background Holland & Crosby, a Toronto, Ontario-based screen-printing operation, was born from the merger of Holland & Neil and J.W. Crosby Advertising in 1997. In 1999, Scott Crosby and Richard Labiuk, partners in the new venture, recognized that they needed to re-equip much of the plant in light of changes in the Toronto graphics market. The market had become increasingly competitive, resulting in growing pressure on profit margins and increasing print-quality demands. At that time, Toronto had the highest installed base of four-color inline screen-printing presses in North America. Over the next 18 months, Holland & Crosby installed a new two-color inline press and new screen-processing equipment. Despite the new equipment, however, the results of process-color printing were unpredictable, which frustrated Crosby, who headed up sales. Labiuk, who ran production and had a background in the offset-lithography and gravure industries, also was concerned with the lack of process control he saw in the company's screen-printing procedures. Both realized that just installing new equipment wasn't enough. To optimize profit margins and get high-quality results on a consistent basis, they had to improve existing work practices, processes, and systems. Too much time was being lost in production that affected the bottom line, and quality was still a variable. So the company brought on Chris Taylor, a screen-printing consultant with experience in color management, who now works with the Chromalogic Group (a Toronto-based prepress film provider). After discussing the problems Holland & Crosby was encountering, Taylor determined that a proper color-management system was required to overcome the shop's problems. At a subsequent meeting with Taylor, the printing company's management team was presented with the benefits of a color-managed approach to printing, which involved standardizing procedures and working from pre-established tolerances, sometimes referred to as "printing by the numbers." After witnessing the presentation, the partners realized that this approach made much more sense than the way that production was currently conducted at the shop, and they chose to follow the consultant's recommendations. "This was a very critical decision," Labiuk explains. "But it forced us to measure all parameters, which is the backbone of total process control." Crosby and Labiuk decided then and there that Holland & Crosby would implement a full-blown color-management system, and they asked Taylor to head up the production team. A year later, the color-management system was up and running and the company was seeing the benefits on its bottom line. Still, there were still many challenges to overcome to fine tune the system. Making color management work Crosby, Labiuk, and Taylor recognized from the beginning that to make this pro-ject work, they would have to overcome resistance to change and get the commitment of upper-level managers and the support of the production team. "If you don't have senior management buying in and promoting and driving it, this [color-management process] will fall apart on its own in no time," Crosby explains. "These guys bought in, especially our plant foreman, and they would help push it whenever there were any issues. And Taylor was in the plant everyday addressing any resistance." Keeping the project on track was another serious challenge. Despite being supportive of the project, the staff tended to resist change when under pressure—especially since the plant was being re-equipped at the same time. People tended to resort to tried solutions when problems came up, even though they didn't always understand the cause of the problems. When busy, the last thing anyone wanted to be bothered with was carrying on with the task of overhauling how they screen printed. When the partners began the process of implementing the color-management system, they reviewed existing procedures and decided to start from scratch. The first step was to develop standards for each element of the production process. They realized that some of the standards would have to be developed empirically. Much of the documentation covering standards evolved through the process of implementation. These standards, which are still subject to ongoing upgrades, are used today as the reference against which all stages of purchasing (e.g., film, ink, etc.) and processing (e.g., screen coating, press setup) are measured. "It's all about controlling as many of the variables as you can—because there are still many that you can't—and then documenting the data," Crosby notes. Prepress The first step in the standardization process was film production. The partners had to ensure that the service bureau that produced their film positives understood what they were trying to do, was technically competent, and could consistently produce accurate film to the company's standards. This meant the film provider had to know Holland & Crosby's tonal curves, screen angles, and halftone rulings and would take responsibility for checking the results with a transmission densitometer. Taylor's knowledge of film production was very beneficial at this point (Figure 1). Screen stretching For screen stretching, the company decided to stay with the two outside services that it was using at the time, because there were no cost benefits to bringing stretching in house, given the volume of screens the shop used. The company contacted its screen suppliers and explained what they were doing, pointed out what they would require in the future, and asked for comments from the suppliers. The company agreed upon several screen sizes, mesh counts, and tension levels for different applications and received a commitment from the suppliers to support tension levels within 18-20 Newtons across each screen. This was considered to be the most stable range, given the size of Holland & Crosby's presses and the variety of substrates that the company printed. Higher tension levels created problems such as mesh ripping when printing on rigid substrates, and the problem only could be avoided through lengthy setups. Taylor made it clear that they would be checking every screen for mesh count and tension against the agreed standard when it was delivered. On one occasion, the company experienced some unexpected moiré, and through its system of standards, its staff was able to track the problem to a difference in mesh count between the warp and weft threads of 18 threads/in. The suppliers were notified, a tolerance was agreed upon, and the screenmaking company gladly rectified the problem. Screen coating Holland and Crosby acquired an automatic screen coater. Crosby says that he "doesn't know how anyone could coat large screens consistently and accurately without one." This was a critical step in ensuring that color consistency could be achieved. The company established a standard coating thickness of 2.5-3.0 microns over mesh as optimum. Its standards also called for checking the Rz factor of screens to ensure good screen-to-substrate contact. Taylor recounts an instance, after the system had been set up, when the screen coater decided (without telling anyone) to save time by no longer putting a face coat of emulsion on screens. "We ran into problems with the job, and because of the system we were able to locate the problem," he says. The company then held the equivalent of a public hanging, resulting in a renewed commitment to maintain the standardized coating procedure. "It's amazing what it takes to get everyone to buy into the system, as everybody still wants to weave their magic in-to the process," Crosby says. "This is the only way that it can be done—following the rules...no exceptions." Screen exposure and washout Next, the company determined optimum exposure time, basing this time on stencil hardness rather than resolution (or a compromise between the two). This approach meant that they would lose some resolution, but they corrected for this by adjusting the tonal curves where necessary. Press setup The company's press beds were checked for bed flatness and anomalies using a 50%-tint linear film (Figure 2). The 50% tint was exposed onto screens and printed, then the print was measured with a reflection densitometer for inconsistencies. Using this method, it was determined that one of the press beds needed to be adjusted. Once the correction was made, the company was ready to move on to the next step: "fingerprinting" each press. For this test, the company had its service bureau produce a linear test film stepped in 1% increments from 1-100%. In setting up the press, all variable parameters (off-contact distance, squeegee pressure, and floodbar settings, etc.) were set to zero, then adjusted incrementally until optimum print quality was achieved. From the final test prints, the company was able to measure (Figure 3) the dot gain or loss they could anticipate across the tonal range and calculate tonal curves for each press accordingly. With gain becoming predictable, the reflection densitometer became the most important tool in the plant. The company's typical gain proved to be approximately 18-21% in the mid tones with halftones at 45, 55, and 65 lines/in. Today, the company checks the dot-gain levels every 25-50 prints, depending on the run length (Figure 4). This allows them to detect variations caused by changes in stock thickness, squeegee swelling, and similar issues. At the same time that they were standardizing setup and fingerprinting their presses, the partners had discussions with their ink manufacturers about their desire to match process colors based on SWOP standard densities. The ink suppliers said they could match Holland and Crosby's requirements. As part of the company's standard procedures, draw downs are now made from each ink delivery, compared against a retained wet sample, and checked for density. If the ink is out of spec, the manufacturer is called in. With the new systems in place, it was no longer necessary to take ink in and out of the presses to adjust densities, which allowed the company's ink department to focus on color matching spot colors, instead of performing black magic on process-color formulations. Today, the standard press-setup procedure is to back off all the settings to zero, then adjust the squeegee pressure until the printed dot area is within ± 1-3% of the standard tonal target level on all color bars. Subsequent colors are printed within the same tolerances as the first color down. When images contain areas created by two colors (e.g., orange), the company keeps the tolerances even tighter. Substrates According to the company, this is one of the most difficult variables to control, especially with styrene materials. Holland & Crosby won't buy from certain substrate suppliers because of quality variations, such as color, thickness, and surface energy. This emphasizes the importance of suppliers in the effort to manage color. If anything in the supply chain breaks down, the end result is compromised. Proofing "One of the first jobs we did after we completed the implementation of printing by the numbers was to run without a proof," Taylor says. "I hid this [proof] in my desk and we relied totally on the densitometer readings. The results really helped to confirm staff buy-in." When a file is received from a customer, a proof is produced on the company's Epson inkjet printer and compared to the original. This proof accurately represents what will be produced on press and is taken to the customer for sign off. If the customer has supplied a proof, this is compared to the Epson proof, and if the proofs closely match, the file is sent to the service bureau for film making. If there is a difference, however, the salesman on the account will take the two proofs to the customer for a decision—if the Epson proof is not accepted, H & C will adjust the file until a match is achieved. Once an Epson proof is approved by the customer, no one—including the customer—is allowed to change anything. There is no more analyzing color or using color keys for visual matching. Predictability has been the biggest result—now any shift, day or night, with minimal supervision, can hit the numbers or the job will not run. Maintaining standards Crosby and Labiuk point out that it was a significant achievement to implement the system, but say that implementation was only the beginning. Ensuring the continuing success of the program requires the commitment and dedication of the company's entire production team to monitor the process and keeping standards current in the light of new materials and suppliers. "Everything we can control we do, so we match closely to the signed proof." Crosby says. "There are things we can't control, such as substrates, but now we have tremendous peace of mind. The other thing we have is predictability of production.... We do produce on time and this greatly helps our productivity because we do not have to reschedule jobs or rerun those that went wrong." He adds, "Most customers don't even know that they are not getting the same quality through a run. They don't look at each print. When you tell a customer that you can systematically reproduce each print the same, he will tell you that he's getting that now. But he assumes this, and if he hears of a complaint, he is told typically that it was a reject and shouldn't have gotten in the shipment. That is one of the most difficult concepts to get across to print buyers." When asked what were the major benefits from the color-management program, Crosby reeled off the following list: • happy customers • better productivity • peace of mind • no more reruns • faster setups • ability to run a job without using a proof once the initial proof has been approved by the customer • no press proofs • faster run speeds on single-color presses • can maintain the same color accuracy using different presses • can provide accurately matched color regardless of print process used (e.g., screen, lithography, inkjet, etc.) • reduced waste • no supervision of the second shift required for color approval—there are no variations between shifts. • reduced ink inventories for process-color inks • color matchers don't have to modify process-color inks Make the move to managed color Many print buyers have been brain-washed into thinking that if they require a quality process-color job, it has to be printed with lithography, or if they want it produced by screen printing, that it must be printed on a four-color inline press. With a color-management system in place, a screen printer can achieve high color accuracy, even with a single-color press (although it may take longer to print). Regardless of the press type used, if the variables are not controlled, it is difficult to maintain color consistency throughout a run, the risk of waste during setup increases, and press proofs become necessary. Without a color-management system in place, it's nearly impossible to match a proof without adjusting ink density on press. But adjusting ink density alters the gray balance and tonal range of the image, so bringing the print in line with the proof often requires large shifts in ink density. The result is that a dominant color area in the image can be matched, but usually at the expense of other areas, so the print becomes a compromise rather than an accurate reproduction. Without color management, maintaining color accuracy throughout the run is difficult, and it is even more difficult to accurately repeat the job at a later time. Screen printers have made significant progress over the last 25 years in identifying and understanding the variables in the process, but for many shops there is still black magic involved in process-color printing. If screen printing is to remain a viable process for the graphics producer in the face of inkjet technology and other changes confronting the industry, greater efforts have to be made in controlling the variables and improving efficiencies. For shops like Holland & Crosby that have made the move to full color management, the benefits have proven well worth the effort. About the author Graham West is president of Wyndham-West & Associates, Inc., a consultancy for small- to medium-sized enterprises that is based in King City, Ontario, Canada. West's background includes experience in all stages of screen-printing production. He has also worked in sales and marketing positions for industry manufacturers, including Sericol, Autotype, and Nazdar.