Paper Terminology

Written by Geoffrey Eisenberg, Vice President of Operations at Tidewater Direct

One of the most daunting, yet important aspects of print buying can be understanding paper. Misquoting or misrepresenting paper to the end user can be a costly and damaging mistake. Below, basic paper buying terminology is reviewed so that print buyers can better understand what to ask for during a bid, and also speak intelligently with their clients regarding paper selection.

Basis Weight

A paper basis weight is a measurement of the weight of 500 equally-sized sheets of paper. There are 6 common measures of basis weight:

Book: 25” x 38”
Bond: 17” x 22”
Cover: 20” x 26”
Index: 25.5” x 30.5”
Bristol: 22.5” x 28.5”
Tag: 24” x 36”

For example, typical 50 lb offset paper is measured in Book Weight; it weighs 50 lbs for every 500 sheets sized 25” x 38”. Similarly, 500 sheets that measure 17” x 22” and weigh 20 lbs are called 20 lb Bond. Ironically, 20 lb bond is very similar in weight (though not exact) to 50 lb offset, and are often used interchangeably. It is common practice for paper manufacturers to insist on a ± 5% deviation on basis weight.

Understanding basis weight is critical to the print bid process. If a print buyer wants 60 lb paper and some vendors bid as book weight while others bid as cover weight, the entire bid process can be thrown off.

Caliper

Paper caliper is a measurement of paper thickness. Caliper becomes especially critical when meeting postal specifications, such as 7 pt and 9 pt. Many common basis weights, such as 50 lb offset, carry a common paper caliper (.004” in that instance). Nevertheless, many mills insist on a variance of ± 10% for caliper. It should also be noted that paper caliper does not necessarily correlate to paper basis weight – in other words, it’s possible to have a .0038” caliper sheet of paper that still weighs out as 50 lb basis.

In general, the most critical aspects of the paper should be communicated during the bid process; lower basis weights are generally bid on basis, while it’s more common for heavier basis weights to bid as caliper. Understand that when paper is bid for caliper, it is important to include the type of basis (cover, index, tag, etc).

Brightness

Brightness is a common term in measuring the amount of impurity (lignin) has been removed from the paper stock, on a scale of 0-100. Mills use many techniques, such as bleaching and using additives to achieve brighter paper. Common brightness for offset paper in the United States is 92 (foreign paper often ranges from 94-96), while newsprint can be as low as 65 bright. Coated and specialty papers can vary based on the grade, so if brightness is critical to the campaign, it is important to specify during the bid process.

Opacity

Paper opacity is a measurement of the light that passes through a paper stock. In the papermaking process, the hardwood and softwood fibers interweave to create natural paper opacity; papermakers may use additives like clay to increase opacity. While paper opacity is generally good in most standard paper grades, additional opacity (classified as “opaque” may be necessary for a particular product. Many financial reports are printed on opaque paper, and opaque paper is a common solution for jobs with significant ink coverage when bleed-through is not an option. Because opaque paper requires special additives and techniques to achieve it’s inherent property, it tends to cost 30-50% more than standard offset.

Coated vs Uncoated

Coated paper uses the same basis weight measuring system as uncoated paper. The primary difference is the coating that is applied to one or both sides of the paper (often referred to as coated-one-side or coated-two-side; c1s or c2s). The coating offers enhancement to the printing surface; ink tends to sit on top of a coating rather than soaking into the paper fibers, causing the image to “pop”. Other characteristics, depending on the finish, can also be improved or augmented. When coating is applied to paper, a certain amount of that paper’s basis weight is referred to as “coat weight”. This means that it takes less pulp to make coated paper than it does to make uncoated, when comparing the same basis weight. For example, 50 lb offset (uncoated) is a thicker, more rigid sheet than a 50 lb coated sheet. All the same, 500 sheets of each weigh the same 50 lbs. Coated papers come in a range of finishes from very glossy to very rough (called matte).

Finishes

Whether specified or not, all papers are “finished” to some degree, coated and uncoated alike. Coated papers are most commonly associated with different finishes, with matte and gloss being the most common. Within those two finishes there are a few others that are more loosely defined, like satin and dull.

While the papermaking process is very similar in creating matte and gloss finishes, the method of smoothing the paper is called “calendaring” in which the paper is woven through a calendar stack. The degree to which a paper stock is calendared determines the gloss of the paper; a shorter calendar stack will produce a rougher finish, which a high gloss product is run though a much larger series of calendar rollers (also called super-calendared). Offset papers with no coating can be calendared as well, creating a very smooth finish. Vellum papers are very rough, and are calendared very little, if at all.

In general, it should be noted that the more calendared a product, the thinner the caliper. The basis weight remains unaffected.

Groundwood vs Free Sheet

Groundwood is a process in which an entire log is ground up and used in the papermaking process, resulting in a less-bright product suitable for less enduring applications like newspapers and magazines. In other words, groundwood pulp carries higher impurities than “free sheet”. Most uncoated grades above 50 lb are considered free sheets, unless otherwise noted. Coated sheets can vary depending on the grade. Naturally, groundwood sheets are less expensive than free sheets.

Coated Grades

Coated papers are graded on a scale from 1-5, with 5 containing the most impurities, the lowest brightness, and lowest quality and cost. #4’s and #5’s are common in the newspaper and magazine markets, while grades 2 and 3 are more common in the direct mail market. #1 grades are premium papers and are very bright, opaque, and of the highest quality. These are most common in sheetfed and digital applications. Specifying a grade in a bid request is a common way to standardize the bidding process, allowing the print buyer to ensure comparing apples to apples.