Mimeo Lounge

Paper - It’s All White To Me

Posted on October 1, 2007 at 3:44pm, written by Frank Romano, Professor RIT

Brightness and whiteness are confusing paper properties because they are not the same thing but they both affect the way we see printing on paper.

Brightness is a measurement of light reflecting off the paper at a standard single wavelength of the visible spectrum. Artificial bright­eners, such as fluorescent additives, can affect the color re­pro­duction because most are not neutral in color and have excess blue reflectance.

The higher the number, the brighter the sheet. Brightness refers to the amount of light a sheet reflects (0 to 100 percent, usually exceeding 90 percent). Whiteness refers to the color of the reflected light (either yellow-white or blue-white—warm or cool). For uniformity across all uncoated white paper grades, International Paper has set its standard at CIE 145 whiteness. So much for the 1-100 scale.

Whiteness contributes most to our perception of a paper’s appearance. Papers with high whiteness values lean toward bluish-white.

Designers are said to have demanded brighter paper and mills responded by making their papers brighter by adding titanium dioxide and by tweaking the shade to the blue-white spectrum. In paper production, a high whiteness level is achieved by the use of bleached pulp together with high light scattering filler pigment. Additives such as Fluorescent Whitening Agents (FWA) and shading dyes are added.

Paper can be equated to a light bulb because it reflects light and thus becomes a light source. Most coated and uncoated papers are manufactured to a blue-white shade because, to the human eye, the blue white shade appears brighter.  A balanced (or neutral) white shade of paper reflects the total color spectrum equally, while a warm white shade absorbs the blues and cooler colors. A blue-white shade will absorb the warmer colors and reflect more blues or cooler colors.

International Paper recently announced to its North American customers that its entire range of uncoated freesheet papers for imaging, commercial printing, envelopes, and forms would be improved to a new standard of whiteness and brightness. The company is also transitioning the way it describes its products from the old GE brightness standard to the CIE whiteness scale.

In the U.S., brightness is the traditional measured value that appears on most reams of paper. Whiteness was developed as a single value to describe the appearance and appeal of paper. It is said to be more accurate than brightness with regard to the human perception of shade.

Stora Enso asks if paper must be whiter than white? If you want to reproduce as many shades in a picture as possible, then the background—that is, the paper—has to be neutral. The greater the difference between the whiteness of the unprinted parts of the paper and the printed sections, the more distinctly we see the color. The paper therefore has to reflect as much light as possible, while the printing ink must absorb a maximum of the shades that are not to be reproduced.

The higher the CIE whiteness of a paper, the more it leans towards bluish-white, while the more yellowish-white papers achieve lower whiteness values. Brightness and whiteness affect readability (too much light tires your eyes when reading lots of text) and the sharpness of photos (too little light reflected makes photos appear muddy). Do you want to achieve a cold feeling or a warm one? A bluish-white paper is the best choice for the first impression. A yellowish-white paper for the second.

Test results have shown an improved color rendering quality with increased CIE whiteness value up to a certain level. Any further increase in paper whiteness does not contribute to an improved color reproduction quality. In other words, more whiteness does not make better printing.

What is the magic number? Legions of consultants, designers, and printers will argue about it to the end of time.

Who would have thought that white paper would be a point of argument?

Tags: brightness, coated, frank romano, paper, uncoated, whiteness