Paper: It’s a Question of Brightness

If I told you that white catalog paper can have the same brightness measurement as a trendy purple sheet, you’d probably wonder from which planet I hail.

But it’s true. Brightness often is a critical determinant in paper specification, but it’s an attribute whose measurement has fallen prey lately to a wide variation.

That wasn’t always so. When first established, it measured the brightness of pulp by evaluating and controlling the degree of bleaching during the pulp-cooking phase of production. Pulp manufacturers used uniform processes and instrumentation to assess brightness, which resulted in an apples-to-apples comparison and a consistent standard to help classify grades of paper.

However, things are different now; ambiguity has taken center stage in many quarters of the paper industry. Today, a brightness measurement reflects the brightness of the pulp and the paper.

Why does that matter? To influence brightness, most white paper manufacturers use some level of fluorescent whitening agents (FWAs). FWAs increase the “perceived whiteness” of paper. Bear in mind, they’re not inherently bad, but they do pose some problems.

For starters, paper that has achieved its brightness through the use of FWAs can’t be measured in a meaningful way for that brightness, because different brightness instruments currently in use (e.g., Datacolor Elrepho, Technidyne ColorTouch) read FWAs differently. In other words, the same sheet of paper can have different brightness measurements depending on the equipment used to evaluate it. (This is one reason some foreign sheets have higher reported brightness levels than U.S.-made sheets.)

Moreover, controlled conditions and standardization are lacking when it comes to the characteristics of the filters, the light sources (that is, a light’s UV content at the moment of measurement), the direction of the light, the mode of observation, etc.

Ambiguous results present a predicament for every paper specifier selecting product based on the convenience of a brightness measurement. Without knowing the degree of FWAs, the measurement process and the instrumentation used, how can you fairly judge different papers simply by a brightness number? The simple answer is that you can’t.

Should you care how different papers achieve the look of brightness? That is, should you care about the amount of FWAs added? Yes. All white paper manufacturers add some FWAs. But the more FWAs added, the more brightness will change depending on the light source in which it is viewed (i.e., daylight vs. indoor fluorescent).

So suppose you’re a high-end fashion marketer who places great importance on the accuracy of printed fabric colors and textures in your catalog. If you’re using a base stock that achieves brightness through excessive amounts of FWAs, what you approve for color at your printer isn’t going to look the same as what your customers see in their living rooms.

How to Determine the Importance of Brightness: Three Steps

The following three steps can help give you a clearer view of the brightness quotient in your paper-specifying duties.

1. Look at those situations under which a brightness value actually has some merit — for instance, within the same manufacturer’s lineup of paper products.

At Tembec, we use the same process and instrumentation to appraise each brand in our publication papers portfolio.

Each brand is distinguished by a brightness number, as well as other attributes.

2. Understand the difference between “brightness” and “whiteness.”

I noted earlier that a white sheet can have the same brightness value as a purple sheet. This is possible because, by definition, brightness is the light reflectivity of pulp or paper measured as a percentage in the very narrow blue range of the color spectrum. “Whiteness,” on the other hand, considers the entire color spectrum. Since, as was mentioned earlier, FWAs are added to enhance “perceived whiteness” (and we know now that perception will change depending on the light source), it makes more sense to evaluate actual whiteness in the paper you’re looking to use.

In fact, brightness has no connection to any specific color. In time, its use as a number to describe optical properties has evolved into a false assumption by some people that it’s interchangeable with whiteness, which is not so. A whiteness determinant considers the entire visible spectrum, and therefore, it’s a better representation of the actual visible appearance of the paper.

3. Consider carefully the role brightness plays in your decision-making process.

What are the most important attributes you need in the catalog paper you buy? If it’s smoothness and gloss for a uniform lay of ink, then look specifically at smoothness and gloss properties. Brightness doesn’t give you the crisp dot mandatory for great printing, nor does it help you cover the sheet with more and more ink, as is the current trend among art directors.

Or perhaps you want trouble-free performance on press and in the bindery? Brightness won’t minimize web breaks or influence fold strength.

Maybe you need opacity for an end-use application requiring minimal show-through. A high level of brightness doesn’t guarantee opacity, and it actually could have an adverse effect on it, depending on what was done to achieve that brightness.

Conclusion

Please don’t misunderstand: A paper’s brightness can be a good indicator of its degree of lightness and/or darkness, which is really the degree of grayness/dinginess you see in it. But the introduction of FWAs really has clouded the entire brightness issue.

In short, the role brightness plays in the specification of paper may be overrated. There are other attributes that are much more important, such as smoothness, ink gloss, uniformity and runnability. After all, if the paper doesn’t perform on press, what have you got?

Blair J. Alford is director of marketing for coated and specialty papers at Tembec. He wrote this article at the request of the Catalog Success editors. For more information, you can contact him at (800) 527-4897, or visit www.tembec.com.