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Classification and Grading of Papers

Classification of papers

Pulp, paper, paperboard and converted paper products are classified in the U. S. Department of Commerce, Bureau of Census’ Standard Industrial Classification System (S.I.C.) as industry #26.  Pulp is designated at 261, paper 262, paperboard 263 and converted products 264 to 269.  Each broad sector is further divided into significant categories.

For example, information is collected and published for major categories of paper, such as newsprint, uncoated groundwood, uncoated free sheet, coated groundwood and coated free sheet, kraft, industrial and tissue.  Many of these major sectors are further broken down into sub categories.  For example, the uncoated free sheet sector includes such items as bond, ledger, offset, envelope and tablet.  

The classification of grades used by the American Forest & Paper Association (AF&PA) in its statistical reports closely parallel the S.I.C. system.  The AF&PA provides a more detailed breakdown of a Bureau of Census for some grades.

Classifying Papers for Easy Identification

BUSINESS AND RELATED PAPERS

ADVERTISING AND RELATED PAPERS—
      Coated And Uncoated

*The basic size is used to establish the basis weight of the respective grades. The basis weight represents the weight of 500 sheets in the dimension shown.

Denoting Relative Quality  

There are no published standards, specifications or trade customs in the paper industry.  The assignment of a particular grade to a quality category and the establishment of sales policies are made by each individual company.

The only published specifications for printing and writing papers are those issued by the U. S. Government and state agencies for the paper they purchased.  In addition,  buyers may, individually, provide the paper mills with the specifications they require in the paper they plan to purchase.

Letters and numbers may be used to signify a quality difference in some grade categories.  The assignment of an individual grade is determined by the producing mill based on its evaluation of its products relative to those of its competitors.

The numbers 1 to 5 are usually assigned to classify coated papers by quality, with #1 being the highest.  The brightness of the sheet is the most common measure of distinction, with gloss and other characteristics considered in some cases.  Cast coated papers and some other grades considered very high quality are classified as #1.  Coated #2 and #3 qualities consist of coated free sheet papers.  Coated #4 includes both free sheet and groundwood furnish grades.  Coated #5 is predominantly coated groundwood.  However, as noted previously, the classification of the grade is at the discretion of the mill producing the product.

Representative brightness and opacity measures prevailing in the marketplace have been set forth in the following tables.

Uncoated free sheet writing and printing papers are classified by numbers and descriptive words. The lower the number the higher the quality. The words “super premium,” “premium” and “commodity” may also be used. These designators are shown in the tables at the conclusion of this chapter.

The letters “A” and “B” are commonly applied in the marketing of text and cover grades.  A-Text is the higher quality classification and usually represents a sheet with distinct surface characteristics.

Cotton content (sometimes called rag content) papers are classified by the amount of cotton cellulose they contain.  The highest quality paper is 100% cotton fiber.  The most common is 25% cotton but some sheets may be marketed with 50% and 75%.

Brightness and Opacity

The brightness and opacity of a sheet of paper have a significant impact on the appearance and usage of the printed material.

The brightness of the paper surface affects the contrast of tones and brilliance of the printed image, especially when large process halftones are printed. It is measured by comparing the amount of light reflected by the paper surface to the amount of the same light reflected by the surface of magnesium oxide established as the standard of 100%. A common term used in quoting the measure is “G.E. brightness,” although G.E. no longer manufactures the measuring instrument.

Opacity represents the degree of show through of printed matter on the reverse side of the paper; also, the ability to hide printing on an adjacent sheet, as in a book. In reference to paper, it is expressed in terms of percentage reflectance when the sample is backed by a black body versus the reflectance when backed by a white body. Complete opacity represents 100% and complete transparency 0%.

It should  be recognized that mill brand papers comparable in quality, even in cost, may not match the measures shown. By the same token, measurements of brands of some mills may exceed the percentage ratings shown in the tables.