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Aug 30, 2001 12:00 AM
What you need to know about quantity and unit of measure, M weight, basis weight, color, finish and grain
For the newcomer, many aspects of paper ordering can be confusing. Once you know the basics, however, the process isn't quite so intimidating. One quick caveat: each particular mill has its own requirements, so the following information should be used only as a guide. For specific mill requirements, contact your merchant's order department.
Here's an example of a paper order:
|a] Quantity and unit of measure||16 ctns|
|b] Size and M weight||23 × 35-119M|
|c] Basis weight||BS-70|
|e] Description||Mountie Opaque|
Let's examine these components more closely.
This is the number of sheets, number of cartons or skids, and in the case of mill-making orders, the total weight.
Because paper has many different uses, each grade is cut into different standard sizes. Among these standard sizes, however, there is one size in each grade of paper that is used to establish the weight of a sheet. This is called the basic size. The basic size differs from grade to grade. Bond, envelope, ledger, and thin papers, for example, have a basic size of 17 × 22 inches; cover papers have a basic size of 20 × 26 inches. Book, offset and text papers have a basic size of 25 × 38 inches.
Paper prices are given per thousand sheets, hence the “M.” The M weight is the weight of 1,000 sheets cut to the basic size. To determine the M weight, you must know the ream weight. There are 500 sheets of a particular sheet weight in a ream. The M weight is simply double the ream weight. If a ream of 25 × 38-inch paper weights 40 lbs., then the M weight is 80 lbs.
Almost all printing papers are manufactured and identified by their basis weight, which, as previously stated, depends on basic size. It is determined by one ream (500 sheets) of a given paper cut to its basic size.
Strictly speaking, substance weight is the basis weight of bond paper (500 sheets of 17 × 22 inches), but the terms “basis weight” and “substance weight” are often used interchangeably. Note that a ream of some tissue and wrapping grades is considered to be 480 sheets.
According to Grassman's First Law, the eye can distinguish only three kinds of color difference: hue, brightness and saturation. Hue is the visual sensation that distinguishes one color from another. Brightness refers to how color is perceived in a position on a dark-to-light scale, or dark-to-light tones (also called luminosity or tone value). The degree of brightness that can be captured in paper is proportionate to whiteness and directness of reflection. Saturation is how the eye perceives, in addition to hue, the presence or absence of gray (also referred to as purity or intensity).
Paper comes in a wide variety of colors and shades of “white” (ranging from blue to cream and pink). Many of these affect halftone reproduction and the aesthetic appearance of the finished piece.
Under “description,” paper buyers should provide the complete brand name and grade — if the paper is unbranded, give the best general description.
The paper selected must be suitable for the printing process and ink used, as well as adaptable to the physical requirements of the job. Special consideration should be given to factors such as strength, durability, foldability, permanence and opacity.
Finish is the most important physical property of paper. It refers to surface contour and characteristics measurable by smoothness, gloss, absorbency and print quality.
The surface character of paper ranges from fancy to strictly functional. The finish of a text or cover paper is typically selected by a designer to express an aesthetic view, but the paper surface should be taken into careful consideration in terms of the printing process, as well as the desired appearance and feel of the finished piece. High-fidelity halftone illustrations require a glossy enamel finish, making the finish chosen a top priority. If high-bulk paper weight is necessary, a low-finish, antique paper will suffice.
Finishes are created during the papermaking process and may be described from roughest to smoothest. Papers with a smooth antique finish are described as having an eggshell finish. Vellum finish has a high unique surface that is easy to handle after printing. It has a greater degree of ink absorbency, and thus, less tendency to smear. Further smoothing of the paper results in a machine or English finish — the latter is the highest possible finish that can be produced on a paper machine.
Paper machines can produce other finishes, too. A felt-finish paper has a textured surface created by a marking felt, or by the use of rolls with an embossed surface at the press section of the paper machine. In each case, a design is impressed into the paper web while it continues to carry a high percentage of water. Felt finishes are applied to text, cover and superior-quality wedding papers.
Other examples of finishes produced on paper machines include wove, laid and coated papers. Wove is characterized by the impressions of a felt dandy roll covered in a woven wire, with no laid lines. A laid finish is imparted by a dandy roll with wires parallel to its axis that impress the paper to produce a permanent watermark. Coated paper has been treated, either on or off the paper machine, with pigments mixed with water and adhesives to form a substance similar to latex house paint. This coating produces a smooth surface and gives the paper added flexibility. Examples of coated paper are gloss, which also describes the physical property of coated paper that makes it reflect light; dull, a paper with a smooth surface and low gloss; and matte, which has little or no gloss.
The direction in which most fibers lay in a finished sheet of paper is referred to as grain. Fibers flow parallel to the direction in which the paper travels on the paper machine during manufacture.
Grain can influence other characteristics of paper. A sheet of paper will contract more across the grain than it does parallel to the grain. A simple moisture test for determining the grain direction can be performed by moistening one side of the paper and observing the axis of the curl: It will be parallel to the direction of the grain. Paper will fold more easily and smoothly parallel to the grain. Heavier-weight paper, like cover and bristol, may fold without scoring when folded parallel to the grain; scoring will be necessary, however, when folding across the grain. A sheet of paper will generally offer greater resistance to being torn against its grain.
There are two basic classifications of grain: grain long and grain short. Grain long indicates that the paper grain is parallel to the longest measurements of the sheet. The fibers are aligned parallel to the length of the sheet. By contrast, grain short indicates that the paper grain runs at right angles to the longest dimension of the sheet. Fiber alignment in paper with short grain parallels the sheet's shortest dimension.
There are thousands of different brand names of paper with constantly changing specifications. “The Paper Buyers' Encyclopedia” is one way to keep current.
For example, suppose a paper buyer is told that a paper called “Protera Text” has been selected for a particular print job. The paper buyer consults the encyclopedia's alphabetic index of more than 6,000 brands and learns that “Protera Text” is a Premium No. 1 offset recycled sheet, manufactured by Georgia-Pacific. The index also gives a page number in the main section of grades that provides more detailed information. Consulting the main section, the buyer finds that “Protera Text” has a 90 brightness; is alkaline; comes in 60-, 70- and 80-lb. weights; has a printing page-per-inch (bulking information) of 392, 333 and 303; and has opacities of 92.5, 93.5 and 94.5. The listing further indicates it is available in colors, rolls, sheets and cut sizes. In addition, it shows all competitive brands so that the buyer can make alternative selections if necessary.
“The Paper Buyers' Encyclopedia” is published annually and includes contact information for 5,500 mills, merchants, converters, importers and exporters. Its “How to Buy Paper” section features an envelope guide, copier paper guide, and various charts and descriptions.
This article is adapted from the 2001/02 “Paper Buyers' Encyclopedia” by permission of Grade Finders, Inc. (Exton, PA).