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Written by Andy
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Monday, 29 September 2008 12:00 |
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 A description of papers
Basic Size and Basis Weight
The basis weight refers to the weight in pounds of 500 sheets of paper when it has been cut to that paper's standard basic size. For example the basic size for Bond paper is 17 x 22 inches. If 500 sheets (a ream) of Bond is cut to its basic size of 17 x 22 inches and weighs 20 pounds, it is classified as 20 lb. bond. If a 25 x 38 inch ream of Offset paper weighed 60 pounds it would be called 60 lb. Offset, and so on.
Other basic sizes of paper.
Bond 17 x 22
Offset 25 x 38. Because of the way that weight is calculated based on basic size sheets. It's interesting to note that 20lb bond is equivalent to 50lb offset and 24lb bond equivalent to 60lb offset.
Cover 20 x 26
Finish
The finish refers to the surface characteristics of the paper or how the paper feels, is it smooth such as glossy cover or rough with an antique finish? Does the paper have a glossy appearance such as coated glossy papers or is it dull like bond paper. Does the paper have a high ink absorption rate as does Vellum or poor absorption such as on coated papers? Some common paper finishes are described below. - Cockle - A cockle finish simulates characteristics of hand made paper with a wavy, rippled, puckered finish. The effect is obtained by air drying the paper under minimum tension.
- Felt - Felt is a soft texture on uncoated paper that is created during the papermaking process with a either felt covered roller or with a rubber roller with a felt pattern that creates the finish. It can also be accomplished as an offline process. The felt finish does not affect the strength of the paper.
- Gloss - A gloss finish produces a shiny and reflective surface on one or both sides of certain coated papers. A higher gloss is usually seen on higher quality coated papers. The gloss finish is produced from compounds added during the paper making process.
- Laid - A laid finish has the appearance of translucent lines running horizontally and vertically in the paper. It is produced during the papermaking process with a special roller that creates the pattern in the wet paper.
- Linen - Linen finished paper resembles linen cloth and is usually produced after the papermaking process as an offline embossing process.
- Matte - A finish on certain coated papers that is smooth but gives a dull appearance. A matte finish, as well as other types of coated paper, are good choices for print jobs in which high quality is required.
- Parchment - A paper finish that has an old or antique appearance and is the result of washing sulfuric acid over the paper and then quickly neutralizing the acid wash. This process melts the outer paper fibers which fill the voids in the rest of the paper. Parchment is very durable and grease resistant.
- Smooth - A smooth finish is the result of the paper passing through sets of rollers during the papermaking process. This process is known as calendering.
- Vellum - A vellum finish has an eggshell appearance and is consistent and even but not as much as a smooth finish. Vellum is one of the most popular uncoated finishes and paper with this finish has a high ink absorbency rate.
- Wove - An even finish in uncoated paper with a slight texture made by a felt roller covered in woven wire.
Grain
The grain of the paper refers to the direction of the fibers in a sheet of paper. Long grain paper refers to paper in which the fibers run in the same direction as the longest measurement of the paper. In other words an 8.5 x 11 sheet the grain would be long grain, with the grain running down the 11" side. Short grain paper refers to paper in which the fibers run in the same direction as the shortest measurement of the paper. When paper is torn, it will tear easier and straighter when torn parallel with the grain. It will also fold easier parallel to the grain and produce a cleaner fold than if folded across the grain. Laser printers require long grain paper for the best results. Short grain paper may not feed properly into a laser printer and the heat produced by a laser printer may result in the sheets curling as they come out of the printer.
Types
- Uncoated stocks: Uncoated stock is paper that has no coated pigment applied to reduce the absorbency or increase the smoothness. The uncoated finishes can be described as vellum, antique, wove, or smooth.
- Coated stocks: A coated stock has a surface coating that has been applied to make the surface more receptive for the reproduction of text and images in order to achieve sharper detail and improved color density. By adding a coated clay pigment, the objective of coating the stock is to improve the smoothness and reduce the absorbency. Coated paper finishes can be categorized as matte, dull, cast, gloss, and high gloss. The coating can be on both sides of the stock (coated two sides, "C2S") or on one side only (coated one side, "C1S"). Coatings added to groundwood papers give them a greater degree of permanency and the natural tendency for goundwood papers to yellow is reduced.
Opacity
Opacity is the measure (percent) of the amount of light passing through a sheet of paper. Some papers have more fibers and/or fillers and as a result are more opaque than others. Papers containing more fibers and fillers have the ability to hold a printed image without showing through to the backside as easily as papers without as many fibers and fillers. Just because a paper is thicker does not guarantee that it is more opaque than a thinner paper. Some thinner papers may be more opaque because there are a greater number of fibers and/or fillers in their composition.
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