Printing Paper Guide

Metric Basis Weights

Over the past several years an ever increasing amount of the printing papers sold in the United States is coming from overseas. While most of the mills importing into the U.S. have adopted the U.S. standard of pounds to identify the basis weights of their grades, several products are still labeled in metric terms. Listed below is a chart that shows the U.S. standard in terms of basis weight and the equivalent weight listed in Grams per Square Meter (GSM). Please note that while U.S. weights will vary between grade classifications, under a metric system all grades are measured by the same standard.

Formula to Calculate    -    Basis Weight x 1406.5        =   GSM

                                            Basis Size Width x Length

Whiteness vs. Brightness

For over 40 years one of the key measurements of any grade of paper has been brightness. Generally speaking, the brighter the paper the better the contrast between the paper and the ink. A brighter sheet is easier to read, and colors tend to pop off the sheet when compared to the same printed copy on a sheet that is less bright. Brightness has also been an indicator of the quality of the grade, as brighter sheets are ranked higher and typically cost more. This has been true for both coated and uncoated papers. Brightness has always been measured using a G.E. Reflectance Scale. It is actually a measurement of the reflection of light off of a grade of paper, with 1 being the lowest reflection, or what would be given to a totally black grade, and 100 for the brightest measured grade. Over the years the paper industry has improved the manufacturing process, so that today many premium grades have brightness ratings of close to 100, the maximum rating possible under the G.E. system.

Over the past few years, as imported papers  have gained a larger foothold in the domestic market, a new term has been introduced. Whiteness is now often referred to when evaluating grades of paper, with a C.I.E. (International Commission on Illumination) measurement used for rating.  What is the difference between whiteness and brightness? We have already explained that brightness measures the reflection of light. In doing so it actually measures only a limited amount of the full color range. Whiteness measures the full spectrum of visible light, and provides a measurement more closely aligned with what our eyes actually see. Put another way, on a scale of 1 to 10, brightness reflects a color range approximately between 4 and 8. Whiteness, on the other hand, measures all of the colors in the range, from 1 through 10. As a result we may have 2 grades of paper that measure the same on a brightness scale, but because of a difference in shade they look different to the eye. This can be the case when you have 2 grades of opaque that measure 92 on the G.E. brightness scale, but one is a warm white and the other is more of a blue white. Their brightness rating is the same, but the paper looks different because of differences in shade. In this example there is 1 common  measurement for brightness, but 2 separate measurements under a whiteness scale.

The trend in paper making is toward whiter and brighter paper. Paper is becoming a global product, with imports coming in at an increasing level. Whiteness is a global standard, and we anticipate a growing acceptance of whiteness as a key measurement tool. Giving exact comparisons between the G.E. Brightness scale and the C.I.E. Whiteness scale can be difficult, since the range of colors measured will vary. We have listed below some general comparisons. Please note the highest rating on a brightness scale is 100, while whiteness measurements will go much higher.

Brightness	Whiteness Range
84	94 - 98
92	138 - 148
96	148 - 155

Reply Cards or Post Cards

A standard post card or reply card must be rectangular in shape, with a minimum size of 3 ½” x 5”. In order to qualify as a post card with its accompanying lower postal rate, the paper used must be a minimum .007” thick.  The card can be as large as 4 ¼” x 6” and still carry this lower rate. If either dimension exceeds 4 ¼” x 6”, however, it no longer carries the post card rate, but rather First Class Letter rate. In addition, it must be printed on a paper stock that is a minimum of .009” thick. If the card falls below these minimums then the mailer must pay a higher rate, potentially as much as $.13 each. While the minimum caliper applies to the post card, there is flexibility to go beyond the minimum and still receive the lower rate. Both sizes can be produced on paper as thick as .016 and still qualify. This provides a great deal of flexibility on paper selection, with improved durability and print surface.

Here are some grades stocked by Athens Paper that meet these requirements. They are ranked by their relative cost, with 100% being the least expensive grade.

7 Point Minimum

Williamsburg 75 lb. Return Card – (100%) Guaranteed .007 thick, this is the least expensive grade. It is very porous, however, and is best suited for simple line copy.

Domtar 90 lb. Index– (170%) A hard, smooth finish with a better print surface than the 75 lb. reply, yet still relatively inexpensive. Available in a 92 bright white or colors.

Utopia 3 100 lb. Matte Coated – (175%) An 87 bright sheet, with good print reproduction on both sides.

Accent Opaque or Plainfield Opaque 65 lb Cover – (187%) Both grades have good bulk, stiffness and brightness and are capable of producing quality 4-color process work.

Knightkote Matte 105 lb Return Card – (195%) A #1 matte with a brightness of 92, this sheet provides better stiffness and contrast than Utopia 3. 

Cornwall or Carolina C1S 8 Pt  – (219%) Use for 7 pt requirements. Good coated surface on one side for quality 4 color printing, with uncoated back side that easily accepts pen or pencil. Both grades are available in a 7 point from the mill, and both are available in C2S.

Kromekote C1S 8 Pt– (342%) With a brightness of 92 and ultra smooth cast coated finish, this is the best choice when premium print quality is required. Also available in C2S

9 Point Minimum

Williamsburg 97 lb Return Card – (100%) Same printing characteristics as the 75 lb.,

Domtar 110 lb. Index – (170%) Same characteristics as 7 pt.

Plainfield Opaque Vellum 65 lb Cover (152%) – Vellum is mill item. Toothy finish.

Accent or Plainfield Opaque Smooth 80 lb. Cover – (187%) Good print surface

Knightkote Matte 135 lb. Return Card – (195%)  Same characteristics as 7 pt.

Altima Gloss 100 lb Cover – (215%) # 3 Gloss Cover. Not available in rolls.

Cornwall or Carolina 10 Pt C1S – (219%) Same characteristics as 8 Pt

Kromekote 10 pt C1S – (342%) Same characteristics as 8 Pt

Paper Characteristics and Their Effect on Printing

Basis Weight – The weight of 500 sheets of a standard size of paper. The standard size will vary according to group classification (bond, offset, cover, index, tag, vellum bristol).

When choosing which basis weight to use take the following considerations into account:

1. Opacity : heavier sheets provide more opacity. If show through is a problem consider going up one weight.
2. Bulk: heavier sheets of the same grade are thicker
3. Stiffness: the heavier a sheet the stiffer it is. If a client is printing a brochure with few pages, a heavier sheet may help make it feel more substantial.
4. Cost: Every time you go up one basis weight in the same grade you increase the paper costs from 15 to 20%. The reverse is true where you will save money as you drop in basis weight.
5. Mailing Weight: The weight of the individual sheets of paper will determine if a mailed piece is over or under the desired mailing weight.
6. Folding: Heavier sheets are harder to fold and may require a score.

Caliper – The thickness of a sheet of paper measured in thousands of an inch. Also referred to as bulk. Sometimes the caliper is referred to as Point, with a point indicating one thousands of an inch. Using this terminology, a 10 point cover is a cover sheet that is 10 one thousands of an inch thick. A 12 point SBS Board would be 12 one thousands thick. A 24 point board would be 24 thousands of an inch thick, or twice as thick as a 12 point.

On most commercial printing grades caliper is not a major consideration. The exceptions are:

1. Post Cards: must be a minimum of 7 point and a maximum of 11 point to qualify for post card rates. If a post card does not meet standard dimensions for length to width ration, the minimum caliper required raises to 11 point. It is important that you check to be sure any grade specified for a post card meets these minimums.
2. Pages per Inch: This term refers to how many sheets of paper it takes of a specific grade to measure one inch. Since one sheet equals 2 pages, you double the number of sheets in an inch to find the pages per inch. This becomes important when quoting on a hard bound book or a perfect bound book. Not knowing how thick the paper is could end up causing problems in the bindery, or even create a situation where the finished pages are too thick to fit into the cover. It can also come into play when printing pages for a 3 ring binder. Using a thinner sheet will allow more pages to fit into the same binder.

Brightness – This is a measure of the reflectance of a sheet of paper. The most common method of measuring is a GE reflectance meter, with the higher the number indicating the whiter the sheet. 

1. Brightness is one of the main physical characteristics used to classify grades of paper. This includes both coated and uncoated grades. In both categories as the brightness level goes up, the grade of paper is classified as a better grade.
2. On uncoated papers, the brighter sheets of paper typically have more opacity than those with lower brightness levels.
3. Brightness provides more contrast between the printed image and the paper, giving the printed image a sharper appearance.
4. Generally speaking, the brighter the grade the more expensive it is.

Whiteness – Similar to brightness, but this is a measurement of what the eye actually sees rather than a measurement of reflectance. Since the eye picks up the color blue, a blue white sheet may appear to be a lot whiter than a red white sheet that measures the same or more on a reflectance meter. Not typically shown as a standard paper specification, it does explain why there are so many shades of white.

Smoothness – A measurement of how level or smooth the surface is on a sheet of paper. Generally only measured on uncoated sheets. Measured using a Sheffield Smoothness tester, with a low number indicating an extremely smooth sheet and a high number a very rough or toothy finish.

1. On uncoated papers, the smoother the finish the better the print reproduction.
2. Rough finishes are referred to as Vellum or Antique
3. Vellum finish papers absorb the ink quicker, dry faster and allow for more dot gain.
4. Smoother sheets have less bulk than do vellum finish papers. The same grade of paper in the same basis weight can vary by as much as 20% when going from a smooth to a vellum finish. This can be important if a client wants a book to look more substantial, but does not want to pay more. A vellum finish can increase the overall thickness of the book for no more money.
5. Most grades of offset and opaque sold in our market have smooth finishes.

Grain Direction – Paper comes from trees, and trees have fibers. When these fibers end up on a paper machine they all become lined up in the same direction. Since fibers are longer than they are wide, the long direction of the fibers in the paper is referred to as grain direction. A sheet that is 25 x 38, grain long has the fibers running the long way in the 38” dimension.

1. Grain direction is important in heavy weight papers that require a fold. It is difficult to fold a heavier sheet across the grain without cracking.
2. All papers that are run through a laser printer should be run in the grain longthrough a laser printer. Be sure when doing this that the images are stripped onto the form in such a way that after they are cut down they are 8 ½ x 11, grain long (in the 11” dimension).

Opacity – The amount of show through from one side of the paper to the other. Measured on a scale of 1 to 100, with 100 indicating the highest opacity possible. This is a very important consideration when printing on both sides of a sheet of paper.

1. Uncoated papers have more opacity than coated papers in the same basis weight.
2. The higher the grade ranking on an uncoated sheet, the greater the opacity.
3. Coated papers go down in opacity as their grade ranking goes up. Higher quality coated papers have more coating and less wood pulp and bulk, the 2 characteristics that add to opacity.
4. Heavier weight papers have more opacity than lighter weights in the same grade.
5. Design plays a large part in the need for opacity. Heavy coverage on both sides of the paper eliminates the need for high opacity. Heavy coverage on one side with light coverage on the other increases the need.

Grade Classifications – Coated and uncoated papers are ranked into certain grade classifications based on key physical characteristics. These classifications are used to give the buyer some general idea of the quality level to expect when specifying a grade of paper.

1. Coated Papers – Ranked according to brightness and gloss. Similar grades should have comparable brightness and ink hold out and reproduction. No reference to opacity.
2. Uncoated Papers – Ranked by brightness and opacity.
3. Grades in the same classification should fall in the same general price range.

Comparable Grades – Grades of paper manufactured by different paper mills that are listed in the same grade category are considered comparable grades. As a result, if a customer asked for Vintage Gloss or equivalent, any coated grade that is considered a #1 coated (as is Vintage), would be a comparable grade.