Printing Problems And Solutions

Front 1

8 main causes of printing problems

Back 1

1.chemical
2.mechanical
3.temperature
4.humidty
5.paper
6.ink
7.machine
8.methods

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catchup

Back 2

ink builds up on the plate
-too much ink, not enough dampening

Front 3

tinting/toning

Back 3

improper ink dampening balance

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scumming

Back 4

spots in the non-image areas

Front 5

adjusting ink is easier than changing paper

Back 5

if FS is too acidic, it will prevent ink from drying

Front 6

piling in the image area

Back 6

caused by paper dust, builds up on the blanket

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linting

Back 7

individual fragments, paper particles cause print problems reducing tack of the ink reduces the problem. solution= more dampening

Front 8

ink trapping

Back 8

causes color variations. how one ink sticks to another influences tack of ink and ink film thickness, a thin ink won't trap properly over a think ink

-the stickiest ink get printed first
-calculated from ink densitometers, can measure a percentage

Front 9

dry trapping

Back 9

a wet ink sticks to a dry ink

Front 10

hickeys

Back 10

printing defect- surrounded by a white halo du to particles of dirt

Front 11

gloss ghosting

Back 11

chemical ghosting- happens during printing - wet ink can occur a ghosting due to the chemistry in ink

eliminate by: fanning it out or varnishing

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mechanical ghosting

Back 12

due to ink starvation- heavy coverage on the lead edge of one sheet

-not enough ink to print form

Front 13

mottle

Back 13

usually colour variation (cyan and magenta) due to uneven porosity of the paper

-the heavier the paper, the greater the mottle

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halftone value transfer

Back 14

improper pressure between the plate and the blanket

-irregular appience in the image

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slurring

Back 15

squeezing the image -slurred- caused loosely tightened blanket (too loose)

-a round dot becomes an ellipse

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doubling

Back 16

ink from sheet foes onto the blanket and shows up on every sheet

-eliminating the sequece, eliminates the problem

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register

Back 17

accurate positioning of the image- tremendous impact on quality
-easy to see

Front 18

screening

Back 18

higher the screen value the greater the dot gain

Front 19

whiteness and uniformity

Back 19

colour of paper greatly effects the colour of the image

Front 20

quality control/measurement techniques

Back 20

quality of materials
must be able to MEASURE and DEFINE

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colorblindness

Back 21

1% woman
7% men
-usually red and green

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Colour and Quality

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VERY SUBJECTIVE
- need customer press approval

Front 23

color measurement

Back 23

measure dot gain, print contrasts, trapping

Front 24

densitometry

Back 24

old process- pull sheets, measure density
new process- scan density at full speed

-wet ink film will be higher than a dry ink film

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grey balance

Back 25

printed without black (CMY) using tints to produce a neutral grey

Front 26

dot gain

Back 26

dots always grow in size, the paper is porous, need to know about the paper
-uncoated vs coated

-can sharpen the dots,

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Densitometer

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handheld device used for a few measurements or automated device for lots of measurements (width of sheet)- colour bars are inline with the ink zones

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LAB

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L- how light/dark
A- how red/green
B- how blue/yellow

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measurement of gloss

Back 29

done to enhance the image, varnish used to add protection (from scratching)

-folding boxes/book covers- popular for varnishing

Front 30

surface finishing

Back 30

film lamination- popular in food packaging
-speeds up the drying process
-costliest
-produces highesst gloss and protection
ex tetra packs

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SF- optical effects/gloss

Back 31

more noticeable if they gloss (on the shelf)

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SF-protection from Abrasion

Back 32

protects the sheet, enhances the image can add wax to be abrasion resident

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SF-resistance

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popular in packaging, labels, banners and environmental issues exposed to humidity

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enhancement and finishing

Back 34

if you use a coating you don't need as much spray powder

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coating

Back 35

1.print varnish
2.water-based aqueous coating
3.UV vanish

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varnish application

Back 36

typically on ink without a pigment
press varnish- varnish turns yellow (fades)

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UV varnish

Back 37

done in one pass, completely seals the paper, hardens instantly (drys instantly)

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embossing

Back 38

puts a texture on a sheet, unlimited types

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hot foil stamping

Back 39

done on a letterpress machine, typically metallic colours

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holograms

Back 40

authentic products
-credit cards, money, NBA