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Paper Properties and Their Impacton the Printing Process
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Why is Knowing Paper Important to you?Why is Knowing Paper Important to you?
1) Paper and other substrates on which an image is printed can represent 25-55% of the final cost of a printed job
2) Having a working knowledge assures that the paper selected is the most appropriate and cost effective for the application
3
Basics of Paper ManufacturingBasics of Paper Manufacturing
1. Forests
2. Logging – debarking
3. Pulp refining
4. Forming Section (wet end), Press Section (water removed), Drying Section (sets moisture levels)
5. Calendaring (final stages for smoothness, etc)
6. Cutting down the 40,000 lb plus rolls ready for finishing (rolls or sheets)
6.
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Paper Making Kit
Plus, a Question
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Paper Machines are the length of football fields!!!Paper Machines are the length of football fields!!!
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Key Properties of PaperKey Properties of Paper
Fibers
Basis Weight
Caliper (Thickness)
Grain Direction
Formation
Surface Sizing
Opacity
Brightness
Whiteness
Absorption
Smoothness
Paper Strength
Stretch
Moisture
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Wood Fibers Used in Paper ManufacturingWood Fibers Used in Paper Manufacturing
The fibers used in paper manufacturing play a key part in what happens to it later
•Hard woods
•Southern climates
•Shorter fibers
•Weaker, yet smoother
•Coniferous trees
•Northern climates
•Longer Fibers
•Stronger, yet rough
•Eucalyptus trees
•Southern hemisphere
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Fibers Used in Paper ManufacturingFibers Used in Paper Manufacturing
Paper can be made from MANY sources, but wood fibers are used more often
Other paper fibers sources can include:
• Cotton and other plants (i.e. hemp)
• Recycled fibers
• Hemp
• Rice
• Even old jeans!
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Basis Weight of Paper ---- Huh?Basis Weight of Paper ---- Huh?
Basis Weight is paper weight in pounds of a ream (500 sheets) in it’s basic size
Web Printers purchase paper by weight (pounds) in rolls. Sheet fed printers typically order by number of sheets needed for the job.
Example:
The basic size for Book papers is 25” x 38”. The measurement of basis weight for book paper would be calculated by taking 500 sheets each measuring 25” x 38” and placing it on a scale. If the weight of the 500 sheets was 50lb., we would call that paper 50 lb. Book. If the weight was 60 lb. it would be 60 lb. book.
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Basis Weight Types – Basic SizesBasis Weight Types – Basic Sizes
1) Cover (20” x 26”)
a. Heavy weight papers used for book covers, advertising, direct mail, etc.
2) Index (22 ½” x 28 ½” and 25 ½“ x 30 ½ “)
a. Usually available in smooth and vellum finishes. Used in file folders, index cards, etc.
3) Tag (24” x 36”)
a. Smoother surface than index, making it ideal for high-speed folding, embossing, etc.
4) Bond (17” x 22”)
a. Commonly used for letters and business forms. Example: paper in your books is 20# Bond
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Basis Weight Types – Basic SizesBasis Weight Types – Basic Sizes
5) Board (22 ½” x 28 ½”)
a. One of the board grades, with a softer surface than index or tag. Used for POP, signage, book covers (soft), advertising etc.
6) (25” x 38”)
a. Coated Book
b. Uncoated Book
c. Text
d. Offset
Much easier outside the U.S.…
They use only one Basis Weight.
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Let’s look at some
Swatch Books
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Basis Weight as compared to CaliperBasis Weight as compared to Caliper
Basis weight is the weight in lbs of a ream of paper in its’ basic size
Caliper is the thickness of the paper
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FormationFormation
Formation is the physical distribution and orientation of fibers and other solid constituents in the structure of a sheet of paper which affects the appearance and other physical properties.
Formation is also referred to as “look through” because the formation can sometimes be observed by looking through the sheet.
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FormationFormation
Formation can have a big impact on print quality for:
a. Ink Mottle - A “wild” formed sheet will result in the ink absorbing into the structure unevenly which then causes the ink to day with a mottled appearance.
b. Ink Show-Through (Printed Opacity) - If a sheet is “wild” with areas of fiber surrounded by areas of no or little fiber, ink will bleed at differing rates resulting in a strong “blotchy” ink show-through.
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Surface SizingSurface Sizing
Surface is a key to good press runnability!
a. Uncoated papers need to “seal” the sheet to reduce press contamination (fiber, debris, etc.).
b. Sizing used for uncoated paper consists of a starch applied to the paper during the paper making process.
c. Various types of starches are used: Corn Potato Ethylated Cationic Starch Oxidized Etc.
Good surface sizing is critical to achieve good press performance!
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Surface SizingSurface Sizing
Starch is applied by a simple “coating device” located between the two drying sections of the paper machine. There are several types used by paper makers to applied starch. A typical size press would look like this:
Paper
Size Press Rolls
Starch Solution
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Optical PropertiesOptical Properties
1) There are five main optical properties that influence the visual perspective of a printed sheet:
a. Opacity
b. Brightness
c. Whiteness
d. Color
e. Gloss
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OpacityOpacity
Opacity relates to the show-through of the printed image from the opposite side of the sheet, or the sheet under it.
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BrightnessBrightness
Brightness affects the contrast, brilliance, snap or sparkle of the printed sheet. It is the percent of reflectance at a standard single wavelength.
a. Don’t confuse “whiteness” with “brightness”.
b. Whiteness is the amount of Red, Blue and Green reflectance and that will be discussed shortly
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73-78.973-78.9
79-82.979-82.9
83-84.983-84.9
85-87.985-87.9
88+88+
AF&PA Brightness ComparisonAF&PA Brightness Comparison
81.9 and below81.9 and below
82-86.982-86.9
87-90.987-90.9
91 +91 +NO.1NO.1
NO.2NO.2
NO.3NO.3
NO.4NO.4
GE BRIGHTNESS GE BRIGHTNESS METERMETER
PremiumPremium
Old New
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WhitenessWhiteness
1) Whiteness is the ratio of Red, Green and Blue reflectance.
a. An attribute of a diffusing surface which denotes its similarity in color to preferred or standard white.
A psychological attribute of a color stimulus. A “white” color stimulus is perceived as void or any hue or grayness.
b. White can be in many different hues.
Known as “cold” if on the blue side.
Known as “warm” if on the red side.
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GlossGloss
1) Gloss is the relative amount of incident light reflected from a surface.
a. Paper Gloss - Degree to which a paper surface appears “shiny”.
b. Printed Gloss - Degree to which a printed ink appears “shiny”.
2) Paper Gloss is attained by the paper maker through calendering and pigments.
a. The higher the calendaring, the higher the gloss.
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CalenderingCalendering
Paper
Calendar Rolls
Pressure and heat combine to make the sheet shinier and glossier. However, the more you calendar, the thinner the sheet becomes.
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Coated Paper Finish ExamplesCoated Paper Finish Examples
Finish Calendering Paper Gloss Surface Suggested
Matte None Not apparent Rough/toothy, non-glare
Texture, Text
Dull Minimal Very Low Smooth, non-glare
Illustrations, Black & White
Satin/Velvet Light Low - Moderate
Smooth and soft to the touch
Text, texture, fabrics
Silk Light Moderate Smooth and silky to the touch
Fine art, skin tones, detail, readability
Gloss High High Smooth, shiny, slick
Hard, shiny surfaces, no scuff
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Gloss Finished SurfaceGloss Finished Surface
Calendared using smooth and polished steel rolls
Smoothest surface
Highest printed ink gloss
Highest plain paper gloss of coated finishes -- reflective
Highest ink hold-out, lowest dot gain
Best for showing fine detail
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Matte Finished SurfaceMatte Finished Surface
Non-glare surface
Textured, Roughest
Minimally calendered
a. Lowest paper gloss
b. Lowest printed ink gloss
c. Greatest amount of contrast
between paper and ink
Replicates look and feel of uncoated
End Uses: Text, charts, anywhere to minimize eyestrain, writeable
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Silk / Dull Finished SurfaceSilk / Dull Finished Surface
Non-glare surface
Micro-embossed surface,
pattern from imparted by calendar rollers
Excellent ink holdout for sharp halftone reproduction
Softer images
Richer halftones and solids than mattes
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Velvet Finished SurfaceVelvet Finished Surface
Coating formula and on line calendaring technique produce a smooth, low gloss paper
Looks like a dull -- prints like a gloss
Higher paper gloss than a dull
Similar coat weight to gloss
Smoother, harder surface than a dull
More uniform printing surface than a matte
Distinctive, silky feel
A.K.A. Satin, Suede
Global Coated Papers: Worlds of DifferenceGlobal Coated Papers: Worlds of Difference
North American AsianEuropean
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Uncoated versus Coated PapersUncoated versus Coated Papers
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Uncoated SurfaceUncoated Surface
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Un-Coated Print DotUn-Coated Print Dot Coated Print DotCoated Print Dot
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SmoothnessSmoothness
Measures texture and topography
Necessary for continuous, non-mottled ink film
Higher ink gloss
More pure ink color/broader tonal range
More accurate reproduction
Greater detail for critical colorProductsCorporate Identity
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StrengthStrength
1) Strength of paper is more dependent on the nature of its fiber than its thickness.
a. High bursting strength is achieved by closely intermingling long pulp fibers during the forming of the sheet on the paper machine.
b. Fibers are long and tear in the cross machine direction is always higher than tear in the machine direction.
This is because the greatest number of fibers lie across the path of the cross machine.
c. Tear strength is important when producing a sheet with perforations. The “perf” should not fall apart of be difficult to separate.
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StretchStretch
Stretch is the amount of distortion paper undergoes under tensile strain. Stretch is generally much greater in the cross direction than in the machine direction.
a. Excessive stretch with web or sheetfed papers will result in poor registration or fanning problems.
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MoistureMoisture
The Moisture content is the percent of moisture found in the finished paper.
a. Can range from a low of 4.0% to a high of 7.0%.
b. Heat-set web paper with low moisture (< 5.0%) will dry out in the heatset oven causing cracking at the fold.
1 ton of paper at 5% moisture level will contain 100 lbs. of water!
Remember earlier when we talked about the paper machine? Paper is 95 to 98% water as it enters the paper machine! Moisture in paper plays a
part from the beginning all the way through the printing process.
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MoistureMoisture
Paper likes to come to equilibrium with its environment.
a. Paper brought into a humid pressroom absorbs moisture at the edges while the rest of the pile or roll (towards the center) will remain unchanged.
b. As this process occurs, the edges containing more moisture will increase in size resulting in wavy edges.
c. Paper brought into a dry pressroom will give up moisture, at the edges first, shrinking the paper resulting in tight edges.
This will result in wrinkles, fanning and bad registration.
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Specialty Grades of PaperSpecialty Grades of Paper
Fancy finishes
Synthetic Papers
Magnetic Papers
Pressure Sensitive (i.e. “sticky back”)
Carbonless
Etc
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Educational ResourcesEducational Resources
1) Spicers Papera. Environmental calculator
b. other tools
2) International Paper Pocket Pala. www.ippocketpal.com
3) The “Coated U” from Appleton
4) Sappi Standards
5) Paper mill swatch books
6) Many more!
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OFFICESCorporate Office 800-774-2377 or 562-698-1199Los Angeles 800-774-2377 or 562-698-1199Las Vegas 702-736-4441Phoenix 800-352-5749San Francisco 866-774-2377Denver 303-373-9655Portland 800-452-8401 or 503-405-0100Seattle 253-518-0015 or 800-231-5136Honolulu 808-832-0001Minneapolis 877-634-0024Kansas City 888-333-0055St. Louis 314-801-6100Salt Lake City 801-364-0113 or 866-403-6609