Selecting the right paper for your magazine

Defining paper quality, whether recycled or conventional, depends on defining your magazine's needs.

Printing salesmen like to draw little triangles on their pads to inform you, the print buyer, that their plants will provide the best of "price, quality and speed." They tend to acknowledge the lack of harmony among these three attributes, but vow to juggle them with aplomb. You want all three ingredients perfectly balanced: You want to pay just enough for just the right level of quality on just the right schedule.

One way to become more precise and practical with definitions of quality is to emphasize the function it has in a specific publication. Consider paper: You may be surprised to learn that the grading system for coated paper is based on the single criterion of brightness. This is an excellent anchor for a scale because it measures paper's reflectance, which is going to govern the contrast of printed ink and, a little more subjectively, the brilliance of an image. But to be called a Number 4, a sheet must simply meet the blue light reflectance standard of 73 percent to 79 percent. How it gets there isn't standardized, although that can matter to you, the buyer. Working with paper grade alone is applying a single definition of quality.

A look at paper properties

Besides brightness, paper has some measurable properties with significant visual impact. The focus here is on those that affect print quality with the broadest strokes--although nearly every aspect of a sheet's structure, manufacture and content has some effect. With recycled paper, for instance, you may encounter strength problems compared with conventional, and its degree of smoothness can vary as well. A paper's appearance can be evaluated by its brightness, whiteness, gloss, smoothness and opacity. Without plunging too deeply into manufacturing, you should also make note of a paper's pulp type and its formation characteristics.

* Brightness is measured on a tester that determines a paper's capacity to reflect a particular blue wavelength; reported as a percentage.

* Whiteness is often confused with brightness, but it's an entirely different property.

Brightness measures the reflectance of blue light; whiteness treats the evenness of reflectance of all colors in the spectrum. The brightest paper may reflect a great deal of blue and very little red or green; the whitest papers tend to have much lower reflectance readings, but maintain equal color reflectance--making them neutral backdrops for ink. Finally, the highest reflectance papers may achieve this by reflecting little blue but much of both red and green.

* Gloss is defined by a paper's specular reflection of light rays. Our eyes determine it by noting how shiny or lustrous a paper appears. Extensive calendering or other surface treatments cause a paper to move toward optical flatness--the point at which light rays striking it are reflected back in parallel rays, as they would be from polished glass. At the other extreme, matte finish papers reflect light with great diffusion, scattering the rays in all directions. Publishing and advertising both set great store by high gloss because it tends to work hand in hand with brightness to make printed images sparkle. High gloss actually adds to color intensity by increasing the gloss contributed by the ink itself.

However, gloss for gloss's sake is a dangerous route toward beautiful printing. We see printed color by looking at light reflected through ink by paper. A glossy surface sends the majority of light straight back at us, but it's also busy showing us how much light is falling on it.

* Smoothness is bound up with gloss and another key characteristic, paper formation. Smoothness is what it sounds like, but that doesn't mean it feels like what you may anticipate. Silky finishes and sizings may make a paper feel sumptuous, but smoothness is specifically the levelness of a sheet, which includes its internal evenness. Paper fibers can be compressed from the outside into obedient height, but if the fibers, formation characteristics, and basis weight of the paper require it, this compression results in pockets of greater fiber density. Smoothness isn't tested with a finger tip, but with an air-leak tester that measures the rate at which air passes through the sheet. Formation and smoothness can be examined by looking through a sheet to see how evenly translucent it is, and whether dark or light pockets appear.

* Opacity usually figures in any production decision involving quality. For some magazines, opacity can be sacrificed in pursuit of both greater brightness and lower cost: the move to a lower basis weight of a higher brightness sheet can impart an appearance of higher quality. But opacity, the extent to which light transmission is obstructed, does not come solely from paper weight or caliper. The chief ways to increase opacity are by adding fillers or dyes; by relying on the high light absorption properties of groundwood pulp; by limiting pulp bleaching to maintain a darker and more light-absorbent fiber; and by positioning the paper toward the blue-white, high brightness end, because blues, greens and grays absorb more light than do yellows and reds.

You can already see that there are some very inexpensive ways to build in opacity and some quite costly ones. A high percentage of lightly bleached groundwood is not only the end to show-through, but the mill's dream spec. On the other hand, using costly titanium dioxide pigment is the formula for both high brightness and powerful opacity. From a paper buyer's standpoint, you can pay for opacity in a free sheet, but much less for it in a groundwood pulp paper.

Skillful assessment of reader and advertiser perceptions of quality is the foundation for selecting materials that serve real needs. A definition of quality doesn't rely on that vague adjective alone, but includes an understanding of where quality comes from. Now let's look at the paper grading scale and see what it does and doesn't reveal about quality.

If your magazine is typical, the only thing you figure you have to know about the paper grading system is that Number 4 stock costs more than Number 5, and probably for some good reason. It's already obvious to you, handed sample sheets of each grade, that the 4 looks better, feels better, and prints better than the gloomy 5 beside it. However, by looking closely at the scale's standards, you'll see why this is so, and also why the grading scale is such a general yardstick of quality that real differences between two sheets require more than a number to describe.

Paper by the numbers

Choosing a paper grade is principally a matter of selecting a price range. After that decision is made, the more subtle matter of selecting a sheet that does exactly what you need it to do requires your attention. It's at this point that you choose a paper for its value, not cost alone. And it's here that you'll need to know what the grading system tells you.

Paper grades are defined by brightness specifications, but how a sheet obtains its brightness is arguably as important as how bright it is. It's not unusual for a printing contract to define paper by nothing more than a basis weight and a grade number. This distinction is about as accurate for price as it is for quality, for there are routine pricing differences from mill to mill on ostensibly the same sheet, just as there are differences in a range of properties that are lumped together to constitute quality. Understanding the full range of characteristics of paper, which the grading system classifies very loosely, will reveal the differences among sheets of the same grade, enabling you to buy the particular kind of paper that best suits your magazine's reproduction requirements. High quality doesn't consist of a single property, present to varying degrees in different sheets, but instead includes many attributes, some of which will be more important to your magazine than others.

Before positioning these properties in the grading system, I should acknowledge an important fact: If a Number 6 paper came on the market tomorrow, at a lower cost and lower quality than Number 5s, there would be quite a few publishers anxious to switch to it. And that reflects not so much a boorish attitude toward the finer things as an accurate perception of the value of a substance that often carries materials as fleeting as a newspaper's. It's no badge of honor to spend more on a product than its end users can benefit by. Given the grim fact that paper can account for about half of manufacturing costs, production managers are wise to scrimp on paper to the degree that it doesn't impair the integrity of the product.

Coated paper is loosely classified into six grades, and the sharpest line in the spectrum falls between grades 3 and 4. Grades 3 and better aren't sullied by a lick of groundwood, while some 4s and 5s carry varying percentages of the nasty stuff. Strictly speaking, groundwood content does not define any grade barrier. While other characteristics, such as composition, figure in the classification system, they don't do so with precision, and that means that there will be significant differences among papers of the same grade.

The paper grading system observes some conventions in classification, but specific standards of measurement aren't applied for properties other than brightness, in part because paper is made from a raw material subject to extreme variations. Producing paper to exact tolerances would be like requiring stalks of celery to be precisely uniform. Quality control standards for paper making must allow for variations within a run; how tight those tolerances are reflects the mill's standards, its response to the market's concerns, and the quality of raw materials used in a particular grade or type of paper.

Brightness, whiteness and reflectance
% reflectance of wavelength

Paper               Red     Green     Blue

Ultra White          80      80        80
Super Bright         80      80        85
High Reflecto        85      85        80
Warm Web             85      82        80

Defining paper grades

The top grade has run right off the numbered scale, for above Number 1 is Premium paper. I'm going to lump these two grades together because they share common attributes, differing only in degree, that set them apart from other papers. These stocks are characterized by extreme brightness, gloss and even formation. They're made exclusively from all-chemical pulp: pulp consisting solely of cellulose, with all the lignin removed by a cooking and refining process. It is lignin that haunts mechanical pulp, or groundwood, accounting for its lower strength and brightness, its tendency to yellow, and its coarser formation.

Premium papers are often blade-coated two or three times to ensure mirror-like surfaces. The blade coating process involves application of surplus coating that is removed by a blade governed by a precise metering device to even out the minute peaks and valleys of the coated surface. Matte and gloss finishes are both common to these sheets. Those of us in the magazine business simply call all of them annual report papers, and although they make their way to web presses, are often run sheetfed.

There are some magazines using Number 1s for covers, but it is with the Number 2 sheets that publishers tend to enter the grade scale, and then usually only for prestige covers. Number 2s are again composed of all chemical pulp, and they also rank high in gloss, with brightness readings somewhat subtly down from Number 1s, commencing at 83 percent. They may or may not be double-coated. Like the two grades above them, they start at basis weights of 70# (25 x 38) and climb to cover weights.

At the Grade 3 mark, the coating itself will begin to show some of the compromises lower prices require. A coating includes such ingredients as brighteners, color, adhesives, waterproofing agents, and opacifiers. With Grade 3s, the most costly pigments such as titanium dioxide are replaced or mixed with highly refined clays. These clays tend to provide less opacity and smoothness than titanium.

The brightness specs for Number 3s are 79.1 percent to 82.9 percent, and all in all, these papers tend to be formulated to mimic the higher grades more closely than the lower. Although they fall in the center of the classification system, they aspire to higher status, and do a good job of it.

For most publishing purposes, the grade scale begins at Number 4 because these sheets are affordable--particularly in shorter runs. This is the point at which production managers make decisions about upgrading paper quality. Grade 4s check in between 73 percent and 79 percent on the brightness meter, and how they get there is the real story.

Here we can begin to see the difficulty of using a single measurement to classify papers, because Number 4s may include some mechanical pulp. This is a little like reading those lists of ingredients that say only that the potato chips "may contain one or more of the following oils..." In one sense, the mills can't slip too much groundwood past us here, because they must meet a brightness spec, and groundwood has a mighty tough time reflecting light. More important, as soon as cellulose carries the baggage of lignin with it into the pulping process, other features suffer as well. Tensile strength, formation and resistance to picking are some of the properties affected.

Within this category are all-chemical pulp stocks, boasting brightness ratings at the top of the Number 4 scale. Most Number 4s do contain groundwood, but in varying percentages. To understand both grades 4 and 5, we need to look at groundwood closely.

The term groundwood is quite descriptive of the process, for logs are forced against a grinding stone that reduces them to pulp, and the lignin that binds the fibers together comes right along with the cellulose. The yield per pound of pulpwood is extremely high, and the end product will be high in opacity and bulk.

Papers should be classified as derived from chemical or mechanical pulp, because groundwood is technically a term applying only to the stone grinding process. Also in the grade 3 category are papers made of refiner mechanical pulp (RMP). The RMP process employs a disc refiner instead of stone, and the high heat generated softens the lignin much more than does the groundwood pulping process. TABULAR DATA OMITTED Thus weakened, the lignin and fibers separate to a large degree, resulting in pulp with longer, stronger fibers, which contributes to strength and smoothness. RMP sheets sport brightness ratings of 77 to 79 percent.

Also among grade 4s are papers of thermomechanical pulp (TMP). This process also uses a disc refiner, but wood chips are preheated, softening the lignin still more for better separation from the cellulose. TMP pulp is often run through a second stage of refining as well.

As far as the grading scale is concerned, a paper mill can bring its sheet up to grade 4 level by meeting the 73 percent brightness spec. Adding titanium dioxide will bring groundwood, TMP, or RMP sheets into the brighter ranges. Bleaching, which removes or alters the lignin, can also be part of the secret, and there are several other techniques that help a paper achieve brightness.

It's important to obtain the information on the percentage and type of mechanical pulp in any sheet because it's a strong indication of the paper's potential runnability problems, such as weakness and lack of dimensional stability and its general appearance as measured in smoothness and gloss. Pulp content varies enough to reduce us to generalities, but for reference, grade 4s may contain from 20 percent to 40 percent of mechanical pulp, and grade 5s up to 45 percent. By comparison, newsprint contains 75 percent or more mechanical pulp.

Because Number 4s form the bridge between truly lush sheets and the workhorse on the low end of the scale, the category can be broadly divided into three sections, reflecting both brightness and pulp quality.

From Number 4 to Number 5 is not quite the leap into the abyss, for there are 5s that come very near the 72.9 percent brightness mark that tops the category, and there is a generally accepted base of a 68 percent reading. Technically, there is no bottom to the scale, and paper buyers should determine the brightness of the particular sheet they're using.

Number 5s are certainly going to contain groundwood; it remains for you to learn how much by a call to the merchant or mill. A zone of 35 percent to 45 percent is typical. Now, know your enemy: Groundwood isn't simply a force of evil in the universe. Its advantages include its lower cost, based on the higher yield per log and simpler pulping process, and its inherent opacity. Groundwood fibers are more light absorbent, particularly when bleaching is held to a minimum.

Groundwood's flaws show up on press and in the finished product because its fibers are longer and less obedient. In addition to carrying some lignin, the fibers are torn so fiercely in pulping that they include shives, whole bundles of fibers that resist even formation. A sheet made of groundwood pulp will have pockets of fibers mashed down to varying density; this affects ink absorption and ultimately the even density of printed solids. There are several other ways in which onpress performance is affected, but problems related to formation tend to manifest themselves in appearance, and therefore concern the paper buyer directly.

With all these elements in mind, you can now pursue papers with an eye on all their attributes, and appreciate what each mill may do in its formula to satisfy you and your audience.

Opacity: A tough row to hoe

Factors that increase opacity...

Use of mechanical pulp Adding fillers Increasing coating weight Limiting bleaching Limiting sizing Limiting calendering Limiting fiber refining

tend to diminish these qualities

Brightness Strength Fold crack resistance Whiteness Ink holdout Gloss Smoothness

Alex Brown is president of Printmark, a Montpelier, Vermont magazine management and production consulting firm.

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