• Publishing & printing

Ed #11 Print it.

Ed™ knows printing. Ed wants you to be OK. With press OKs. Next to the initial concept meeting with the client, a press OK may be the single most stressful step in the entire print production process.

It’s where all the hard work comes together and all the decisions you’ve made before are put to the test. It’s the last chance to make sure the project comes out the way you want. It’s the time when fixing problems can cost thousands of dollars—and not fixing them can cost even more.

Ed can help by taking some of the pressure out of press OKs. Ed will tell you why press checks are important, introduce the different types of presses you’re likely to encounter, and tell you what to look for, what to bring and how to get the best results. And while Ed can’t make you an expert overnight, you’re almost sure to find some useful tips for your next trip to the printer.

Why does Ed do it? Because Ed is all about printing—and printing well. Because Ed wants designers, printers and other graphic arts professionals to work together smoothly and continue to set new standards for quality and creativity. And of course, Ed also wants to show you that Billerud should be your first choice for fine printing papers. With Billerud—and Ed—on your team, you’ll do more than OK. You’ll do great.

Ed will never grow old, but some of the information in this issue is out of date.

On presses. Doing the job right starts with the right equipment. So which is right for you?

On presses

Doing the job right starts with the right equipment. So, which is right for you?


In all of their many variations, modern commercial printing presses are marvelous machines. Many have more computing power than was used to land a person on the moon. They can print more colors than Gutenberg ever dreamed of and run faster than a Kentucky Derby winner. And when your job is on press, all of this technology—and the highly skilled employees who run it—is yours to command.

The challenge, the satisfaction and, some might even say, the thrill, is to use all of a modern press’s capabilities efficiently, cost effectively and with maximum impact. And doing so begins with understanding how presses work.

The vast majority of all commercial printing is produced using two main types of equipment: conventional offset lithographic presses and digital presses.

For close to a century, the most common printing technology has been offset lithography, which is based on the simple idea that oil and water don’t mix. Oily ink is applied to the area of the printing plate that contains type or images and is kept from the non-image areas by a thin film of water or a dampening solution. Some offset presses are equipped for waterless printing in which specially formulated inks are repelled from the non-image areas by a coating of silicone.

Offset printing, is so named because the image is not applied directly from the printing plate to the paper. Instead, the image is transferred from the inked plate to a rubber blanket, and the blanket, not the plate, prints the image.

Offset printing offers a number of advantages over direct methods. The surface of the rubber blanket can conform to the paper more readily than the plate itself, so less pressure and ink are required, and the plate lasts longer since it is not being abraded by the paper. What’s more, the image on the plate does not need to be reversed as it does when the image is printed directly.

The two main types of offset presses are sheetfed and webfed. As the name implies, sheetfed presses print on sheets of paper. Web presses print on paper that is pulled from a long roll and then cut and trimmed to size after printing.

While offset printing has long been the standard for commercial printing, in recent years it has been joined by digital technology. Digital printing encompasses a wide range of equipment, from desktop printers to large systems that can rival offset presses for quality, as well as hybrid systems that combine digital and offset technologies.

Most digital systems do away with the film, plates and ink that are part of offset printing in favor of some sort of electrophotographic process. Particles of dry or liquid toner are attracted to an electrostatically charged cylinder that carries the image. The toner is then transferred to the paper or, less often, to a blanket cylinder and heat is used to melt and set it on the paper. Digital ink jet presses use an electrical charge to guide the placement of tiny drops of ink to create a glossy image that can rival a continuous-tone photograph. Hybrid technologies combine digital and conventional offset technology.

Sheetfed, web and digital presses have different advantages, drawbacks and economics.

Sheetfed presses have long set the standard for quality. They can accommodate heavier paper stocks and a wider range of textures and finishes than web presses and can handle finer screens as well. With as many as 12 colors available and the ability to run sheets through the press twice, it’s possible, budget permitting, to print virtually any combination of colors, varnishes and coatings.

With their high capacities and speeds of up to 100,000 impressions per hour, web presses are almost always the best choice for printing large quantities—around 50,000 and up—of catalogs, annual reports and other publications. Additionally, web presses almost always perfect—printing both sides of the sheet in a single pass—so it doubles efficiencies. Web presses usually come equipped with six to eight units per side, or 12 to 16 ink stations total. Typically then, each side has fewer colors than most sheetfed presses offer, but enough for most web projects.

Digital presses have advantages all their own. Printing directly from a digital file rather than plates permits faster turnarounds and lower quantity print runs. Books and brochures can be printed on-demand as they are ordered, eliminating the need to hold large quantities in inventory. Many digital presses offer variable data printing, or VDP, capabilities that allow for the creation of personalized communications with different messages, images or addresses for each recipient.

At first, the acceptance of digital printing was slow due to problems with the technology and the absence of high quality coated digital printing paper. Today, however, these problems have largely been solved. Improved technologies deliver better resolution and color, and some systems can print thousands of pages per hour, making them suitable for larger projects. Yet even now, only a few systems allow for the use of spot colors or textured papers, and variations in the electrostatic charge used to attract the toner can make it difficult to control gradations across the sheet.

Along with different technologies, digital and conventional offset printing also have different economics. Because they require the production of plates, traditional offset presses have high initial costs but relatively low unit prices—once the job begins to run the price per piece drops quickly.

With plateless digital printing, there are no make-ready costs, but the unit price remains essentially the same throughout the run, and production times could take longer, because digital presses usually run slower than conventional offset presses. To determine which method will be most economical, you need to consider the type of job you’re working on, the size of the run, the schedule, the need for customized information and the costs of the appropriate paper. And, of course, you should also talk to your printer.

Press OKs vary from press to press and job to job. Getting the color in a limited edition art catalog exactly right is one thing. Trying to achieve the same level of quality for a mass-produced advertising insert is another. 

Some projects may not require a press check at all, if the proofs are acceptable, you’re confident about the printer and there is nothing unusual when it comes to inks, coatings, special effects or stock. Some designers may also choose not to bother with a press check if they are reprinting a job that they have produced previously. And some print buyers believe that projects that are printed digitally don’t need to be OK’d at all, since the device’s settings are known and can be matched precisely to the proof.

Of course, there are still good reasons to hold a press check—if you’re printing on a challenging stock, for example. Press checks can also help to protect everyone’s interests when printing high-profile projects like annual reports or corporate image brochures. And even the most carefully planned projects can often benefit from a little fine tuning.

The most important reason to hold a press check, however, is that computer monitors and most proofing systems only provide an approximation of what you will see on press. While proofing systems are getting better, it remains difficult to proof metallic inks, spot coatings or varnishes and fluorescent colors. It can also be difficult to predict the effect that colored or textured stock might have on the appearance of the project.

So press checks remain an important step in the production process. And whether it’s a quick once-over or a multi-form marathon, some basic rules apply.

The first rule is that successful press OKs are the result of everything that came before. The design does not contain features, such as hairline crossovers, that are hard to manage. Any special colors you are trying to match have already been supplied to the printer. The images you’ve provided have enough resolution to reproduce well. The paper has been acclimated to the pressroom.

Most of all, successful press OKs are the result of paying attention to the final proof of the project before the job goes on press. You should already be confident that all of the fonts, bleeds and crossovers are correct. You should already have looked at ink drawdowns, which show spot or custom colors on the actual paper that will be used, and all of the color should already be dialed in, so all the printer needs to do is match it. If the job is a reprint or one in a series, the printer also should have reviewed samples of the previous copies, or better yet, unbound, untrimmed flat sheets of the job with the color bars in place. And all of the copy should already have been proofread by a professional proofreader. With press time often costing thousands of dollars an hour, you do not want to wait until the press OK to discover and fix a missing comma.

Another rule for all successful OKs is good communication. To avoid surprises in the results or the final invoice, don’t take anything for granted. Ask questions. Seek explanations. Discuss your impression of the work with the printer and ask for his or her opinion too. And speak in plain English. Unless you really know what you are talking about, don’t say “increase the density of the cyan by 20%”, but say, “the color looks a little weak.” Let the experts figure out how to correct it.

Be flexible. Most large printers run around the clock, which means that your press check could be held at any time. Large projects may require several OKs that are spaced hours apart, or even overnight.

To make things easier many printers have lounge areas for clients. Some even have small rooms where you can work or catch a nap while waiting to review your project. Bring a book or other work to help keep yourself occupied. Make yourself at home, but remember, you‘re actually still at work—and a printing plant may not be the best place to wear flip-flops.

Be prepared. When you go to the printer, wear neutral clothing, since the light reflected from bright colors can affect the appearance of the color. Bring the original illustrations or transparencies and the most recent proof along with a list of any changes that were specified. Although printers usually have some on-hand, you may also wish to bring your own loupe to check the appearance of the halftone dots. 

What you don’t want to bring is a lot of attitude. A press OK is not intended to be an adversarial process, but a collaborative one. Both you and the printer want to get the best possible job within the specified schedule and budget.

So what should you be looking for?

Begin with a once-over. First, scan the entire sheet and compare it to the content proof, such as a blueline, and the final color proof. Make sure that all photos, artwork, and copy are in place, including any special codes or identification numbers. Check carefully to ensure that the sheet incorporates all of the corrections made on the proof. Verify the dimensions of the page and the paper stock.

If all the basics check out, look at everything in more detail. Working under correct lighting conditions, most often found in a special color-viewing booth, check the overall color, corporate colors and any “memory” colors, such as the yellow of a school bus. Compare spot colors to your ink drawdown or the sample you already provided to the printer. Pay special attention to large areas of solid colors, since even slight variations in ink or toner will make the results look uneven. If the project contains images that cross over the gutter, make sure that the color and ink density are the same on both sides. (If the two parts of the image appear on different forms, cut one out so you can hold it next to the other). You should also make sure that any varnishes or coatings appear where they are supposed to and have a uniform appearance.

Check the register by using a loupe to look for dots—or rows of dots—that are hanging at the edges of four-color photos. Good quality four-color process work calls for a register tolerance of .010 of an inch, or a row of dots; and even one color out of register on a four-color job can cause the color to shift, especially when printing cyan or magenta.

You won’t be the only one looking at the job. The printer will also be examining it, using both a trained eye and some special tools including control strips and a densitometer.

The control strips or color bars that appear on almost all sheets are key tools in achieving and maintaining quality printing. Using a densitometer, a small device that measures the amount of light reflected from a printed surface, the printer can use the bars to measure color density, and other factors in print performance.

Even with the best design and preparation and the closest look at the proof, problems can still arise with the ink, the paper, the press, or any combination of the three.

Ink density is a big concern. If the ink layer is not dense enough, colors can look washed out and type becomes thin and pale. Too much ink can blur the images and make the type look fat. Getting the density right is the printer’s job and usually, you shouldn’t try to specify it. After a sheet is approved, however, it’s a good idea to write the densities along the color bar, in case you ever decide to reprint the project. Keep in mind, however, that densities and colors will change as the ink dries, so a sheet that is wet will not look the same as a dry one.

The toners used in most digital printing behave differently than conventional inks. After they are applied, toners are typically baked onto the surface at a high temperature. If the temperature is too hot, however, coated papers can blister.

Other common problems include flaking, or picking, and hickies. Caused by overly viscous ink, undried varnish, overly high printing speeds or poor surface strength in the paper, picking pulls off small fragments of the paper’s surface, producing small unprinted white dots on the finished product. While some presses automatically wash away pick-outs, it may be necessary to stop the press and wipe the fibers from the blanket and plate.

Hickies are small white doughnut-shaped imperfections that are most obvious in large areas of solid ink coverage and the shadows of halftones. They are caused by specks of dirt, dust, dried ink or paper fiber on the blanket or plate, which prevent ink from transferring properly. Hickies are difficult to prevent and, because they are caused by loose particles, may appear and disappear at random during the run.

You may also encounter moirés, offsetting, color shifts and gas ghosting. Doubling, caused by a slight second contact between the paper and the blanket, gives each halftone dot a tiny shadow. Scumming, which sometimes appears as a streak running the length of the sheet, is caused when the ink migrates into non-image areas.

While some issues are relatively easy to troubleshoot, the causes of others are not as clear. Dot gain—an expansion of the size of the halftone dot when it is printed—can darken tint areas and images. It can be caused by the printing film or the printing process. There is also optical dot gain, which is produced by light reflecting from the paper stock. Mottling, which makes images appear blotchy and uneven, can be caused by faulty ink transfer, improper ink and water balance, worn blankets or a poor paper surface. Slurring is usually caused by mechanical problems or ink that is too tacky. Mechanical ghosting can be caused by a number of factors, including high humidity in the pressroom and an improperly laid-out form.

So when do you stop the presses to fix problems? When should you risk the schedule and budget? Some cases are pretty clear—when the CEO’s name is misspelled, for example. And for that matter, any typos reflect badly on you and your client.

Other cases aren’t so easy, especially when it involves more subjective issues like color. Almost always, you’re going to see something that you wish you had done differently, but it may not be worth trying to fix, and if the problem was one that could have been spotted at the proofing stage, you’re likely to have to pay to correct it. Keep in mind that fixating on a single detail or the look of a color in a specific image can throw off the rest of the project.

There are two more things to remember as well.

Just because the press OK is finished doesn’t mean the job is over. Often, there is still folding, binding and other finishing to consider—steps which can have as large an impact on schedules and budgets as the printing itself. No project is really complete until the client receives all of the copies he or she asked for, is satisfied with the results, and pays the final invoice. Only then is the job truly OK.

And remember too that the foundation of printing is paper. Whether it’s produced digitally or on an offset press, printing works by bouncing light off the surface of the paper through the colored films of transparent ink or toner. So the brighter the surface, the brighter the color, and the whiter the surface, the wider the range of the color we see.

There’s more to paper than brightness and whiteness, however. The surface of the paper is equally important. Rougher surfaces tend to scatter the reflected light, which reduces the clarity of the image. And if the ink or toner is allowed to spread into the paper’s peaks and valleys, the printed dots lose their definition. 

Billerud makes the right paper for virtually every digital and offset printing project. We combine optimal brightness and whiteness with a smooth surface that allows for outstanding ink holdout and vibrant true to life color. Contact your Billerud representative for more information.

Doing OKs. Want a good OK? Review the proof. Communicate well. Be flexible. Know what to look for. (And we’ll tell you.)

Press checklist


Bar exam

Printers use color bars and registration marks to help achieve consistent quality and color throughout the project.

Registration marks are used to ensure that the different colors are printed in register, or placed on top of one another. (1)

Crop marks show where the form should be cut. (2)

Fold marks show where and how to fold the sheet. (3)

Dot gain scales for each process color show physical dot gain in different increments. Excessive dot gain can cause images to lose detail and colors to shift. (4)

Trapping—the bond a wet ink forms with an ink already printed on the paper—can be seen using a loupe on the trapping fields of the color bar. Low levels of trapping can make images and type appear washed out.

Screen tint patches, shown for each process color, help assure that screen percentages remain consistent from sheet to sheet.

Color can be adjusted across the color bar. (5)

A series of lines or concentric circles is used to check for slurring. (6)


That’s a moiré

Moirés—the distracting wavy patterns that sometimes appear in printed images—can cause big problems on press. Subject moirés appear when the image that is reproduced includes grid or line patterns that clash with the pattern of the halftone dots on conventional ruled screens. Other types of moirés include screen angle moirés and scan moirés. Moirés can often be prevented by using stochastic screens.


Dry the sheets

Offsetting, or ink setoff, may be one of the most common problems in offset printing. When printed sheets are delivered at the end of the press, the weight of the sheets on top of one another can cause the still damp ink to transfer from the top of one sheet to the bottom of the next. Setoff can be controlled by the use of offset powder, which is sprayed over the wet sheets to help separate each one, aqueous coating or additional drying time.


Be afraid

Gas ghosting, also known as fuming, is typically caused by applying a varnish before the ink has enough time to dry. The fumes released by the drying ink are trapped by the coating, causing the image to show through on the other side of the paper. The problem can be prevented by allowing additional time for the ink to “breathe” and dry before it is varnished.


Red before blue

The sequence in which the ink is applied is important. If magenta is printed on top of cyan, the result can look mottled, cold and blue. If magenta is printed first, the resulting tone will be warmer and look more purple in color.


Get wet

Applied on press with a blanket, low cost water-based aqueous coatings provide good protection from fingerprints and setoff. Because they seal the ink from the air, aqueous coatings can help prevent metallic inks from tarnishing. At the same time, however, the coatings are susceptible to a chemical reaction, or burning, which can cause unwanted color shifts. Light tints of colors—made using a 25% screen or less—are especially prone to burning.


Make a splash

A spot UV coating applied over the water drops adds extra dimension to the image by creating an embossed effect. UV coatings are available in a wide range of finishes and textures, including glitter and tints, and even different scents. Like aqueous coatings, UV coatings are susceptible to chemical burning and can also be difficult to use with conventional inks.


Let’s split

A split fountain can create a multi-color look using one-color equipment. The trough of ink, or fountain, that feeds the press is split into two or more compartments that hold different colors of ink that are then printed on the same plate. With the rise of multi-unit, multi-color presses, split fountains are rapidly becoming obsolete.


Watch your black

Printers use a variety of techniques to produce warm, rich blacks. A solid black—what printers often refer to as “One hit of black”—can be reinforced with a second, 50% screen, of black. It’s also possible to produce a quadtone, or four-color black and white image, or to apply two solid blacks.