Much like the printing industry, paper producers have their own set of lingo that can be confusing. Choosing the right type of paper is important to the physical look and feel of your book. It must also compliment other characteristics such as the text, graphics or images and even the genre of your writing. The paper manufacturing process has become highly sophisticated and there are a number of terms used to describe the aesthetics of paper. Some of these are known as whiteness, brightness, opacity and shade.
Defining the Terms
As the term is used in the industry, paper shade refers to a measurement of the color of paper. A universally accepted color shade model is used to determine paper shade. This is known as the CIELAB model or CIE L*a*b*. Not only is this model used to determine paper shade but other industries rely on it as well. Of all the visual characteristics of paper, shade most closely corresponds with how we see paper in the real world. In book printing and publishing, it is also one of the most important factors for how other elements of a book are perceived. For instance many books use a true white or cream white shade in order to be more visually appealing to readers and cause less strain on the eyes. The colors of text and graphics in a book also influence the shade of paper that should be used. For example warmer colors may call for a more neutral white paper that will work to enhance these elements. Shade may play an important role for trade books such as novels where readers will spend a significant amount of time looking at the pages. A shade that is easy on the eyes will work better to bring out the text.
The whiteness of paper is defined as a measurement of light reflectance. All wavelengths of light are included in this measurement. In a nutshell, there are many different kinds of white. Like shade, whiteness is closely related to our visual perception of the color of paper. Sometimes these variations in whiteness are subtle. For instance two pieces of paper that fall at different ends of the spectrum on the CIE whiteness index may appear white by themselves however when juxtaposed; their variations are revealed. The CIE index assigns a numerical value between 0 and 100 to sheets of paper. The International Commission on Illumination (or CIE) developed the index and it is the most widely used for measuring whiteness of paper in the world. It relies on a standard for illumination (D65) which closely resembles natural daylight.
The type of light paper is viewed under can affect how it looks to the human eye. Other elements such as optical brightening agents (OBAs) used in paper production can also affect the whiteness of paper. For instance when these agents are applied to a dull sheet, the paper will look brighter in natural light and dull in artificial light. When there are little to no OBA’s applied to a sheet, the paper will look brighter in artificial lighting when compared to its counterpart with larger amounts of OBA’s. In terms of book manufacturing, it is important to view proofs of a book as well as any paper samples under different lighting conditions to ensure your other elements (i.e. text, graphics and images) are represented in the best possible way. The whiteness index is meant to be a guide and no matter what it says, perception of color may vary from person to person and from environment to environment.
Like whiteness, paper brightness is measured on a scale from 0-100. It is also a measurement of the amount of light reflected from paper however it is focused on a narrow wavelength of blue light as opposed to all wavelengths in the spectrum for whiteness measurements. The higher the number on the brightness scale, the more light a particular sheet reflects. Brightness is just one part of the equation when determining the visual aspects of paper. Two sheets with identical brightness can look drastically different because shade and whiteness are not taken into account.
In general, there are two measurement systems that are widely used for determining paper brightness. One (used in North America) is the TAPPI scale. The other (used primarily in other parts of the world) is the ISO system. Some papers can have a rating higher than 100 on the brightness scale. This is due to optical brightening agents present in the paper. When these are applied, the paper can actually reflect more light than is coming from the source. An easy way to remember this is the brighter, the whiter. In practical application, if you had a book that featured a historical theme, you may want to go with an offwhite sheet with a lower brightness rating to evoke the feeling of a historical document or something that is old. In contrast, a title with content that is modern would lend itself better to a sheet with a higher brightness rating.
Opacity refers to the show-through or opaqueness of paper. Some sheets may appear to be thinner than others. Papers with lower opacity tend to let text and images show through more than papers with higher opacity. Opacity is expressed as a percentage in paper. For example, paper with 98% opacity means that 98% of light is not allowed to pass through the paper. For books that have many photos, graphics or a lot of ink coverage in general, papers with higher opacity are ideal.
When it comes to choosing the paper for a book, it really comes down to personal preference. Authors, designers, publishers and others involved in the process for making a book may have very specific reasons for choosing one type or grade of paper over another and there really is no right or wrong answer. Knowing the different characteristics of paper and how they influence the content of a book will help guide you to making the right choice.