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Printing Tech: Litho Press, DI Plate, Color Theory, & Paper Traits - Prof. Eric M. Weisenm, Study notes of Typography

Clemson UniversityTypography
Prof. Eric M. Weisenmiller

The intersection of conventional lithographic press and digital press technologies, focusing on the 'sweet spot' for profitable runs, di plate technology with waterless inks, and color theory. Topics include color perception, measurement, and requirements for color reproduction. Additionally, it covers paper characteristics, such as grain direction, important considerations when choosing paper, and paper math.

Typology: Study notes

2010/2011

Uploaded on 11/14/2011

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1. Heidelberg DI:
a. Know the presentation points (not necessarily the actual hands-on demo, but review the movie
found at http://www.presstek.com/flash/DI_demo.html
b. What makes it a hybrid press?
i. Cross between conventional lithographic press and the digital press
ii. Images digitally on the press
iii. Prints from waterless plates or conventional plates onto offset blanket and then to the press
sheet
c. What does ‘DI’ stand for?
i. Direct Image  trademark of Presstek
d. Common run lengths (Where is the “sweet spot?”)
i. “Sweet Spot”: runs of 250 to 10,000 profitably on wide-range of substrates
ii. Feed paper into press of Quickmaster DI with its shorter dimension first
e. DI Plate technology
i. The oleophobic part of the waterless DI plate consists of silicon
ii. Aluminum and polyester are alternatives to the silicon
f. Waterless inks
i. You can run waterless ink in a conventional press, but you can’t run conventional ink in a
waterless press
ii. Almost like gravure
iii. Problem with soupiness of ink when invented bc heat was causing it
iv. Japanese learned that cooling the rollers internally helped sensitive temp variable of the ink
g. Advantages of Waterless Offset
i. Better consistency throughout the runs
ii. Higher densities/greater tonal range
iii. Better ink holdout
iv. Elimination of ink and water balance variable yields reduced running time & waste
v. Better register control
vi. Elimination of paper stretch caused by fountain solution
vii. Elimination of hazardous VOCs & waste water
viii. Higher line screens: 300-800 lpi for better image detail (sharper dots)
ix. Increases print contrast
x. Make ready is cut in half
xi. Higher tack inks
xii. Registers itself
h. Press Testing of the DI
i. The 3 “C’s” of Color Repro in effect:
1. Calibration
2. Characterization
3. Conversion
2. Basics of Color:
a. Color Theory - The Basic Components; Color Separation/Management pp. 69-98, 261-271
b. Basic Process Color Theory
i. 2 Dominant inks provide the objects color. The 3rd ink provides the shape & detail. A skeleton
black provides shadow detail & neutral density.
c. Additive & subtractive color theory & their interaction w/ one another
i. How we see colors printed on a sheet is governed by the interaction between the Additive &
Subtractive Theories
ii. Additive Color System :
1. Uses colored lights RGB
2. Mix different amount of RGB to produce other colors
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Download Printing Tech: Litho Press, DI Plate, Color Theory, & Paper Traits - Prof. Eric M. Weisenm and more Study notes Typography in PDF only on Docsity!

  1. Heidelberg DI: a. Know the presentation points (not necessarily the actual hands-on demo, but review the movie found at http://www.presstek.com/flash/DI_demo.html b. What makes it a hybrid press? i. Cross between conventional lithographic press and the digital press ii. Images digitally on the press iii. Prints from waterless plates or conventional plates onto offset blanket and then to the press sheet c. What does ‘DI’ stand for? i. Direct Image  trademark of Presstek d. Common run lengths (Where is the “sweet spot?”) i. “Sweet Spot”: runs of 250 to 10,000 profitably on wide-range of substrates ii. Feed paper into press of Quickmaster DI with its shorter dimension first e. DI Plate technology i. The oleophobic part of the waterless DI plate consists of silicon ii. Aluminum and polyester are alternatives to the silicon f. Waterless inks i. You can run waterless ink in a conventional press, but you can’t run conventional ink in a waterless press ii. Almost like gravure iii. Problem with soupiness of ink when invented bc heat was causing it iv. Japanese learned that cooling the rollers internally helped sensitive temp variable of the ink g. Advantages of Waterless Offset i. Better consistency throughout the runs ii. Higher densities/greater tonal range iii. Better ink holdout iv. Elimination of ink and water balance variable yields reduced running time & waste v. Better register control vi. Elimination of paper stretch caused by fountain solution vii. Elimination of hazardous VOCs & waste water viii. Higher line screens: 300-800 lpi for better image detail (sharper dots) ix. Increases print contrast x. Make ready is cut in half xi. Higher tack inks xii. Registers itself h. Press Testing of the DI i. The 3 “C’s” of Color Repro in effect: 1. Calibration 2. Characterization 3. Conversion
  2. Basics of Color: a. Color Theory - The Basic Components; Color Separation/Management pp. 69-98, 261- b. Basic Process Color Theory i. 2 Dominant inks provide the objects color. The 3rd^ ink provides the shape & detail. A skeleton black provides shadow detail & neutral density. c. Additive & subtractive color theory & their interaction w/ one another i. How we see colors printed on a sheet is governed by the interaction between the Additive & Subtractive Theories ii. Additive Color System:
  3. Uses colored lights RGB
  4. Mix different amount of RGB to produce other colors
  1. Equal amounts of RGB produce White Light
  2. EX: TV & Spot lights at a concert iii. Additive Color Mixtures:
  3. Red + Blue = Magenta
  4. Blue + Green = Cyan
  5. Red + Green = Yellow
  6. Red + Blue + Green = White iv. Subtractive Color System:
  7. Uses colorants CMY
  8. Mix different amounts of CMY to produce other colors
  9. Equal amounts of CMY produce Black (in theory)
  10. In Reality: equal amounts o f CMY really print dark brown a. This happens because: i. Pigments are not pure ii. Paper is not truly white
  11. EX: filters & ink v. Subtractive Color Mixtures:
  12. Cyan + Yellow = Green
  13. Magenta + Cyan = Blue
  14. Magenta + Yellow = Red
  15. Cyan + Magenta + Yellow = Black
  16. Remember: “I drink my RC cola down BY the river in my GM truck
  17. C = minus R
  18. Y = minus B
  19. M = minus G vi. Printers use cyan, magenta, & yellow to subtract one of the additive colors. These inks are just chemical filters that absorb different wavelengths.
  20. Color perception a. Factors that affect color perception i. Light Source
  21. Type of illuminant
  22. Time of day
  23. Human eye will always adapt to the ambient light source & see it as neutral white adjusting the perception of any colors viewed under it ii. Object
  24. Substrate
  25. Surround iii. Observer (physiological factors)
  26. Color & density measurements play important roles in the process control of color reproduction, but they can’t replace the human observer for final assessment of the color quality of complex images
  27. Human perception is not consistent from person to person iv. Sex (male or female) [EX: females have fewer color deficiencies than men] v. Age vi. Color Vision (EX: color blind) vii. Eye Fatigue
  28. Cones located on the back of the eye are sensitive to red, green, and blue wavelengths
  29. Filters and how they work a. Filter absorbs other light and reflects its color i. EX: Blue filter absorbs red and green light and passes blue
  1. We convert from RGB to create CMYK process separations
  2. All 4 color channels are separate grayscale images
  3. CMYK tint builds (or screen combinations) iv. RGB
  4. R = Red
  5. G = Green
  6. B = Blue b. Digital ranges of above color models i. LAB: -127 to 128 ii. HSL: don’t need to know iii. CMYK: 0 to 100% iv. RGB: 0 to 255
  7. Requirements of Color Reproduction a. Tone Control (Reproduction) i. How many tones can we produce within a range? ii. Objective: to achieve a one-to-one rendition of the tints & shades seen in the original iii. Refers to the lightness & darkness of the highlights, midtones, & shadow areas. iv. Adjust levels b. Detail enhancement i. Techniques
  8. May be accomplished by applying unsharp mask, using a third party extension or by varying GCR/UCG levels, or using special effect options in Photoshop.
  9. Be careful not to overdo effects, or you might lose information.
  10. Unsharp masking c. Color correction i. Where, when, how ii. Worse place to color correct is on press iii. Color correct when RGB because has larger gamut than CMYK iv. Necessary to account for the deficiencies in the inks & substrates that we print on v. EX: magenta absorbs some blue lights it’s not supposed to. Yellow is blue light absorber. To correct, we reduce the amount of yellow printing in areas with magenta in them, resulting in absorbing only the required amount of blue. vi. Why do you color correct?
  11. Inconsistencies in ink
  12. Color cast in picture
  13. Substrate
  14. Deficiencies in scanner
  15. Customer needs
  16. Adjust for printing systems
  17. Lighting during shooting vii. Adjust hue and saturation to avoid gamut warning d. Gray balance/Conversion i. Achieving neutrality ii. The ability to reproduce a grayscale without a cast or overall hue iii. Theoretically equal parts of CMY iv. Actually hue error requires different & unknown percentages of each color v. Adjust curves
  18. Color Separation (RGB to CMYK conversion) a. File characteristics b. Photoshop settings, profiles
  19. Metamerism

a. Metamerism (metamerism failure) is observed when 2 color samples appear to match under a particular light source, & then don’t match under a light source w/ a different “spectral power distribution.” b. Use purple rhem light indicator stickers that shows stripes of diff color in bad light c. Blue & black sock story: looks like wearing same color socks in one light but realize you are when you get into diff light

  1. GCR a. Gray Component Replacement b. Special separating method in digital images whereby the color combinations’ common gray components, i.e. combined equal amounts of cyan, magenta, & yellow, are replaced w/ black. This gives a smaller overall volume of color & reduces problems of color cast due to vibrations in the printing press. c. You can vary the levels of GCR so that you only substitute some of the gray component w/ black d. Purpose of GCR is to reduce the total amount of ink used w/out changing the color. This makes it easier to reach gray balance in print & thereby get a more even print quality e. GCR conversions also result in i. Fewer problems w/ smudging in the printing press bc total amount of ink in press is reduced ii. More accurate colors using low maximum ink coverage
  2. Spot vs. Process Color a. Spot Color: i. Printing inks in special colors, e.g. in the Pantone Matching System. Generally used as complement to black or to achieve a precise color, which 4-color inks can’t provide. Mixed using a recipe. ii. Pantone Matching System: made up of 14 basic colors that mix together to form lots of other colors iii. Commonly used in corporate logos & identity programs, & in 1 or 2-color jobs. iv. When do you use spot colors?
  3. Only want to use 1 or 2 colors in printed product
  4. Want to use colored text w/out risk of misregistration
  5. Imp. certain color is exactly right (logo/ tinted area)
  6. Want to use colors like gold, silver, fluorescent or colors that r more saturated than 4- color combos can manage
  7. Want to have certain color printed w/out rasters
  8. Total color coverage is limited in print b. Process Color i. Colors used for printing, usually CMYK, also called 4-color process. ii. To reproduce a color image, a file is separated into 4 diff colors: C-M-Y-K. When printed on paper, original image is recreated. iii. Process colors are represented as percentages of cyan, magenta, yellow, & black. Varying the percentages offers thousands or color possibilities. iv. When do you use process colors?
  9. Going to print 4-color images
  10. Going to use more that 2 colors
  11. What is a color profile?
  12. Paper Paper & Ink, Chapter 08 a. What is paper made of? i. Primary ingredient on paper is cellulose fibers ii. Can come from trees, cotton, grass/shrubs, bamboo…

length x width x basis weight of given sheet ------------------------------------------------------------------------------ x 2

of square inches in the basic sheet size

Multiply by 2 because a ream in only 500 sheets iv. EX: What is the M-weight for 35 x 45 – 70#. Offset paper? 35 x 45 x 70 ----------------------- x 2 = 232M 950 f. Paper grain i. How/where is it formed?

  1. Grain direction is formed in the direction of the wire on the paper making machine
  2. Grain direction is created at the front end of the paper making machine
  3. Run sheet grain long
  4. Duplicator: grain long runs perpendicular to press cylinders
  5. Presses: grain long runs parallel to press cylinders
  6. Figure out grain direction by tearing & comparing roughness of edges ii. How does it impact a cutting plan?
  7. The sheet has to be run grain long  this determines the cutting plan bc you have to factor in the side of the sheet that is going to be fed first into the press
  8. Always look at the grain direction needs of the finished piece
  9. Watermarks; how/why are they created/used? a. Why? i. Security ii. Prestige iii. Advertisement b. How? i. Etched wire on the “Dandy Roller” helps to form raw fibers
  10. What are the important characteristics to consider when choosing paper? a. Runability i. How well will paper feeds through the press, the 1st^ time and the 2nd, 3rd, & 4th^ time. b. Printability i. Subjective ability to transfer image w/ faithful reproduction c. Amount d. Size e. Cost/Waste f. Cutting g. Binding
  11. Brightness vs. Whiteness a. Whiteness: i. Whiteness of paper is the color balance of paper, what cast of light does the paper have (color cast) ii. Takes more than 1 reading to determine whiteness iii. Can find out with a formula b. Brightness i. Intensity of colors, also called luminance. How light or dark an image is. ii. The percentage of reflectance of light iii. Take one reading to determine brightness; brightness meter reads 1 distinct wavelength of light
  12. Types, characteristics a. Specifying Paper

i. Classes/Categories: bond, offset, index, cover ii. Weight, color, texture/finish, size/grain direction, brightness, basis weight (g/m^2 ), quantity, roll or sheet iii. Coatings: gloss, dull, matte ( in order from shiniest to dullest) iv. Coated: calendered or uncalendered

  1. Calendered vs. Uncalendered a. Paper fibers form peaks & valleys b. Density changes bc of ink film thickness c. Calendaring smooths (irons out the fibers) d. Coating (made of clay) helps to smooth, or add gloss v. Coated vs. Uncoated
  2. Coated: colored ink pigment sits on top of the sheet (ink holdout/retained ink gloss & measures w/ a gloss meter) a. Gloss measures 55 or higher b. Dull measures 21- c. Matte measures 0-
  3. Uncoated: can be smooth or textures, glare free for reading, stronger and more opaque
  4. Calendered
  5. Textured b. Caliper i. AKA “Thickness” ii. Measured w/ Bench Micrometer in thousands of an inch iii. How is it expressed numerically? Verbally?
  6. Offset papers range from .oo2” to .008” a. 2 point stock
  7. Usually don’t say point for .001” stock c. Brightness d. Opacity i. Ability to see through the paper e. Formation i. Pattern of wood fibers ii. Tight or Loose
  8. Press testing: Press Testing & Process Control pp. 364- a. Assess the known state of a Press System b. Used in 440 to determine “goal densities” (how much ink to put down on paper) i. **Goal Densities: can determine with GRACOL standards chart or through running range of densities during press test  run ink at unreasonably high density number then run w/ ink off at very low density number to have range, then work way to middle ranges of density. Use these numbers along with print contrast to get an optimized density for a specific job ii. If ink wet then will read w/ higher meter than if ink was dry c. Measurement information creates “feedback loop” for image optimization d. “Feedback Loop”: If you can measure it you can control it
  9. Why do we press test? How often? a. Why? i. To calibrate press performance w/in a specific workflow
  10. Calibrate is putting something in a known state ii. To determine (& therefore adjust) the quality parameters that can be expected from the press & materials used

i. Hold open: hold off the effects of dot gain or compensate for them b. Print contrast is a measure of the quality of printed screens in the ¾ tones c. PC = SID – 75% tint density X 100

SID i. Goal: 1.7 SID and 41% print contrast

  1. Total Area Coverage (TAC)
  2. Dot gain (TVI) compensation curve a. Tonal Value Increase (TVI): [formerly known as ‘Dot Gain’] the reflection halftone percentage measured on a printed sample minus the original halftone percentage file value that produces it b. Mechanical vs. Optical dot gain i. Always will be some sort of dot gain ii. Mechanical:
  3. Occurs as a result of platemaking or press operations that cause the geometry of the dot to change iii. Optical:
  4. Occurs when light is trapped under dots and thus the dot appear optically larger
  5. Be familiar with the GRACoL specifications. a. ‘General Requirements for Applications in Commercial offset Lithography’ b. A comprehensive set of guidelines for planning and processing work for printers. c. Pertains to all offset lithographic processes and print applications except those covered by SNAP and SWOP, two other industry standards for specific types of printing. d. SWOP ‘Specifications for Web Offset Publications’ e. SNAP ‘Specifications for Non-Heatset Advertising Printing’
  6. G7 –A Calibration Technique a. Based on gray balance b. G7 technique diff that previous GRACoL calibration methods bc it relies on LAB values rather than just densities and TVI c. G7: grayscale and 7 ISO inks (CMYK & RGB –all 7 colors have ISO standards in LAB values) d. Can be used for any print process e. Used as a way to gray balance image  to create standard across board so that it is done correctly f. Takes guess work out of color
  7. Offset Presses a. Press feeding and registration i. study your notes from the paper cutting and feeder demo ii. streamfed vs successive fed
  8. streamfed-
  9. successive fed- iii. the purpose of the “side guide” iv. three point register b. packing- for plate and blanket (amount and purpose) i. plate packing is used to underlay a press blanket or palte to bring the surface to the desired height ii. squeeze .004”- .006”
  10. on MOZ we build the blanket bearer height and build palte to .004” over bearer height iii. c. dampening system options i. continuous/ integrated- ii. ducted- d. Fluid measurement

i. 128 oz =1 gallon ii. 64 oz = ½ gal iii. 32 oz = 1 quart iv. 16 oz = 1 pint v. 8 oz = 1 cup e. dampening solution i. components:

  1. water
  2. acid
  3. gum- eliminate plate/ roller sensitivity/oxidation a. asphaltum gum etch – dampening rollers on the MOZ
  4. oleophilic/oleophobic
  5. aquaphilic/ aquaphobic ii. conductivity- f. Printing Units g. Blankets i. Parts (carcass, polyester liquid resistant layer, rubber face) ii. Blankets (purpose, parts, blanket care, cast vs buff)
  6. Smooth
  7. Buff
  8. Conventional
  9. Compressible
  10. Cast vs buff a. Cast (smooth, (+/- .002”) b. Buff (textured to carry more ink
  11. Press troubleshooting (For example: Symptoms and causes of slur, and other print quality defects) a. Know the major cause-and-effect relationships of print problems covered on the “You Gotta Problem” presentation. Completing the i. Makereadies- lack of focus on pre makeready activities
  12. Mechanical problems reduce productivity and profitability
  13. Solutions: a. ii. Slur- sheet register transfer abnormal, over impression, improper squeeze
  14. Solutions: torque blanket evenly across the width of the cylinder, adjust impression setting, repack plate/blanket iii. b. SHOTs simulator exercise prior to the exam is advisable.