Understanding Paper Stocks: Weights and Finishes
Posted by CBF Staff on
This article continues a series meant to provide customers and readers with a knowledge base of printing industry terms and standards that apply to the products in our online store. Click here to see all of the articles.
Paper stocks are categorized by differences in the manufacturing process, and also graded within these categories by differences in weight or thickness and finish. This article will explain how designations like 100lb book, 20lb bond, and 100lb tag are determined.
Paper Stocks Graded by Weight or Thickness
All paper stocks are graded with a designation of weight or thickness.
A point or -PT designation, used in the North American system, is a straightforward expression of thickness in points, a unit that equals 1/1000 of an inch (.001 in).
The 14PT postcards and rack cards sold in the Creative Business Forms store have a thickness of .014 in.
The 14PT and 16PT stocks we use for our postcards fit into a broader category of papers known as card or cover stock. The 14PT postcard stock is also known as 114lb Cover stock.
The variety of papers manufactured for the printing industry include thin and flexible types like bond and text stocks as well as thicker, heavier card or pasteboard stocks like cover, tag, or index papers. Bond and text papers can be roughly equivalent in weight, finish, and use cases; but, they differ both in composition and the size of the sheets produced in the manufacturing process. The same can be true of differences among cover, tag, and index papers, which differ greatly from bond and text papers but not from one another.
In the metric system, the weight or grammage, is standardized for a square meter sheet in grams per square meter, or gsm. The heavier card stocks can be compared against the thinner papers easily. In the North American system, the weight of a paper stock, graded in pounds (lb or #), expresses the weight of 500 sheets of that stock in its standard sheet size. These basic sheet sizes are different for different types of paper. (See table below.)
A 100lb text paper stock will be a lot lighter than a 100lb cover paper stock, despite sharing the "100lb" weight designation. The 500 sheet ream of the cover stock paper will weigh the same as the 500 sheets of text stock, but the ream of text stock will be shorter in height but much longer and wider than the ream of cover stock. Comparing two sheets of the same size, the cover stock would have a thickness of 11PT and a gsm weight of 270.9 and the text stock would have a thickness of 7.3PT and a weight of 150.5 gsm.
We will provide a table further along in this article that will show equivalent weights in bond, text, cover, tag, and index stocks.
Naming and Grading Paper Stocks by Weight
The table below lists the primary paper types, along with the standard sheet sizes and finish options:
|Type of Paper Stock||Sheet Size||Common Finish Options|
|Bond (Ledger or Writing)||17" x 22"||Uncoated1|
|Text (Book or Offset)||25" x 38"||Coated or uncoated|
|Cover (Card)2||20" x 26"||Coated or uncoated|
|Tag||24" x 36"||Uncoated1|
|Index||25.5" x 30.5"||Uncoated1|
1 Except when chemically treated for use as NCR paper or with carbonless forms.
2 Cover stock should be considered the standard card stock. Tag stock and index stock are also card stocks.
Business forms were traditionally printed on 15lb and 20lb bond papers with carbon sheets interleaved for transferring information from the top sheet down to the remaining sheets. Carbonless forms have largely replaced the messier carbon sheets for this purpose, and they are printed on equivalent 14-16 or 20lb papers. Business forms are sometimes run with the last sheet providing a hard copy on 32lb ledger or on a card stock such as 100lb tag. Our brochures are run on 100lb book paper. 80lb or 100lb book papers are the most common selection for booklets or magazines, and commercial printing for books typically uses Offset paper stock of 50-70lb and may use 80lb gloss text for projects with a lot of photos where the glossy finish is preferred.
Equivalent Weight Chart3
Equivalent weights in different paper stocks are presented in the same row on the table below. The most commonly used weights for each paper type are presented in bold. Examples such as very light card stocks or very heavy bond or text stocks have no practical use in the printing industry. Consider the bold examples an approximate weight range for each paper stock in its real-world use. Values provided are meant for reference not specification. Manufacturing tolerances will vary (most likely within + or - 5% of the value given).
|16lb||40lb||22lb||37lb||33lb||.0032" (3.2pt)||60.2 gsm|
|20lb||50lb||28lb||46lb||42lb||.0038" (3.8pt)||75.2 gsm|
|24lb||60lb||33lb||56lb||50lb||.0048" (4.8pt)||90.3 gsm|
|28lb||70lb||39lb||64lb||58lb||.0058" (5.8pt)||105.35 gsm|
|29lb||73lb||40lb||62lb||60lb||.0060" (6pt)||109.11 gsm|
|32lb||85lb||45lb||74lb||67lb||.00615 (6.15pt)||120 gsm|
|36lb||90lb||50lb||82lb||75lb||.0068" (6.8pt)||135.45 gsm|
|40lb||100lb||56lb||93lb||83lb||.0073" (7.3pt)||150.5 gsm|
|43lb||110lb||60lb||100lb||90lb||.0074" (7.4pt)||161.78 gsm|
|47lb||120lb||65lb||108lb||97lb||.0078" (7.8pt)||176.83 gsm|
|53lb||135lb||74lb||122lb||110lb||.0085" (8.5pt)||199.41 gsm|
|54lb||137lb||75lb||125lb||113lb||.009" (9pt)||203.17 gsm|
|58lb||146lb||80lb||134lb||120lb||.0092" (9.2pt)||218.22 gsm|
|65lb||165lb||90lb||150lb||135lb||.0095" (9.5pt)||244.56 gsm|
|67lb||170lb||93lb||156lb||140lb||.010" (10pt)||252.08 gsm|
|72lb||183lb||100lb||166lb||150lb||.011" (11pt)||270.9 gsm|
|76lb||192lb||105lb||175lb||158lb||.013" (13pt)||285.95 gsm|
|82lb||208lb||114lb||189lb||170lb||.014" (14pt)||308.52 gsm|
|87lb||220lb||120lb||200lb||180lb||.015" (15pt)||312 gsm|
|105lb||267lb||146lb||244lb||220lb||.0175" (17.5pt)||385.06 gsm|
3 The table of equivalent paper weights provided here is derived from information compiled by Micro Format, Inc with permission granted to reproduce it here. It is presented in slightly altered form, but the gsm values and equivalent # weights for the various paper stocks come straight from their research.
Paper Finish Options
Let's examine the basic differences between uncoated and coated papers, and the finish options for coated papers: matte, glossy, and UV gloss.
Coated Papers and Matte, Gloss, and UV Gloss Finishes
Coated papers are chemically treated with a surface sealant, or coating, developed to impart a particular finish (a sheen, luster, or texture) or characteristic (such as decreased ink absorbency, water or UV resistance, or, in the case of carbonless papers, the ability to transfer written information from one sheet to one or more sheets below it). These coatings obviously vary in composition based on what finish or trait they are meant to provide; clay and starches, and polymer blends, chemical additives and thickening agents, including latexes and plastics, are among the ingredients used.
Uncoated stock has not been treated with a surface sealant and should not have UV or aqueous coating applied after printing.
- A matte finish has a flat, non-shiny, smooth appearance and texture suited for applications where superior color contrast and text clarity are essential.
- Gloss finishes possess a high sheen that is sought after for printing projects that emphasize graphics and images more so than text.
- Dull and satin finishes fall between matte and gloss, meant to be smoother and lower in sheen than a gloss finish and possess a texture more like a matte finish. A dull finish is understood to be closer to a matte finish than a satin finish is, but these terms are not specifications, and will vary more greatly in how they are produced by manufacturers compared to matte and gloss finishes.
UV and Aqueous Coating: On Top of the Ink
Finishes like varnish, UV, and aqueous coating are applied after printing, not in the manufacturing process for the paper.
- UV coating is applied as a liquid and hardens by being exposed to UV light. This coating enhances the paper's durability, protects the ink colors from fading from exposure to sunlight, and provides some resistance to water and liquids. The formulation for UV coating has been improved over time, resolving initial complaints that the finish had a yellow hue that adversely affected the appearance of the printed product. UV coating can be produced for a matte or satin finish, but the UV brochures and postcards Creative Business Forms sells are offered exclusively in a high-gloss finish.
- AQ or aqueous coating is a fast-drying, water-based coating that is prevalent in the printing industry. It is perhaps best known, beyond providing the basic protections of an additional layer of coating on top of the ink, for being fingerprint resistant. (UV coating still lacks in that regard.)
NCR paper, named for the NCR Corporation that patented and developed it, is a type of coated paper that was developed as a replacement for carbon paper (another coated paper), specifically to be able to pass information written on a top sheet down to one or more sheets below it. Creative Business Forms' carbonless edge-glued, unit-set, and continuous forms are printed on NCR paper (also known as carbonless paper).
Before NCR paper became the industry standard for multi-part business forms, continuous and unit-set forms were printed on bond papers interleaved with carbon sheets that passed what was written or printed on the top sheet down to the remaining sheets. NCR paper can accomplish this same task between individual sheets of NCR paper without another coated paper in between.
NCR paper features a micro-encapsulated ink or dye on the back side of each sheet meant to pass along information as well as a layer of clay coating on the front of each sheet other than the first. The pressure from writing or impact printing on the first page frees the encapsulated ink on the back side of the page, which reacts with the clay layer it is in contact with to effectively reproduce what was written or printed on the original page.
Edge-glued forms are largely a product of the development of NCR paper and the fan-apart adhesive compound that was developed to bond sheets of NCR paper together: that is, they were not produced using interleaved carbon paper sheets.