GRC 211 ch7-8
True or false: When print stay outdoors for a long time, the colors on the print fade away. This is referred to as ink's color strength
false Color strength measures how much the ink is pigment concentrated, as measured by bleach test
True or false: water pick-up describes how much water can be blended into water-based inks
false Water pick-up describes how much water can blend into oil-based offset inks
True or false: Water-based ink formulation doesn't contain VOC
false (contains less than 20% VOC)
True or false: wax can be used to improve ink film gloss
false: wax increases rub resistance and decreases gloss
property of gravure ink
fluid
ink vehicles
fluid portion of ink that carries pigments
paperboard comparison
for foldability and creasebility, SBS is the highest (then SBB then FBB)
rub resistance
force of friction
inorganic color pigments
inexpensive, good opacity, good light fastness 1. iron oxide, chrome yellow, zinc yellow, iron blue 2. metallic inks (gold from bronze powder, silver from aluminum)
pigments
insoluble in water or organic solvents
tack
resistance of film breaking (stickiness) only applies to offset ink
what type of ink is short ink?
screen printing ink
pseudoplastic
shear thinning
dyes
soluble, brilliant color, low fade and humidity resistance
solid bleached sulfate (SBS)
strongest paper board made of pure chemical pulp excellent printing (high smoothness and brightness) e.g. perfumes, cosmetics, pharmaceuticals, frozen foods
laminated paperboard properties
surface properties (smooth from wax, high barrier) strength properties (puncture, tear) stiffness hydroscopic properties (moisture barrier) polymer adhesion odor neutrality
breakage
tack on low basis weight paper
picking
tack on low surface strength paper
water pick-up value
the amount of water picked by ink only applies to offset ink
ink solvents
dissolve resin, provide a mean of drying 1. VOCs, fluid inks, paste inks
Which of the following ingredients is not used for making ink? a) wax b) plasticizer c) vehicles d) dyes e) fillers
e) fillers
eco-solvent drying mechanism
evaporation
solvent based drying mechanism
evaporation
water based (dye or pigmented) drying mechanism
evaporation and absorption
lightfastness
fade resistance
True or false: thixotropic means ink viscosity increases under agitation like stirring or mixing
false
flatness of corrugated board
(aka warping) thin boards are more prone to warm than thick boards; caused commonly from moisture in environment
colorant requirements
1. color 2. transparency 3. light resistance (outdoor usage) chemical (cosmetics) heat (coffee mugs) oil (food package) rub (wraps)
ink properties and performance
1. drying (boiling point) 2. tack 3. flow (paste or fluid)
working properties of ink
1. how well ink transfers onto substrates 2. pigment dispersion 3. pigment particle size (color strength, hiding power, saturation, gloss, dispersion)
ink oils
1. offset inks: oil-based 2. nondrying oils: mineral oils 3. drying oils: petroleum, linseed, or tung dry by oxidation
ink additives
1. plasticizer increases gloss, adhesion, and ink film flexibility (e.g. cracks on t-shirt) 2. wax improves rub resistance but reduces gloss
problems related to ink drying rate
1. too slow 2. too fast (ink dries in gravure/flexo cells)
white pigments
1. white high opacity 2. opaque ink
organic color pigments
CMY (process colors with high transparent and high fading resistance)
highest strength of corrugated cardboard
SBS
Which of the following statements about ink opacity is NOT true? a) process inks could be transparent or opaque depends on the application b) ink opacity describes the hiding power of ink films c) metallic inks are opaque inks that have high opacity
a) process inks could be transparent or opaque depends on the application Process inks are transparent inks
The newspaper inks often smudge off onto fingers because... (more than one) a) newspaper ink contains mineral oils which dries by absorption b) it is not completely dry c) it is not fully evaporated d) it is absorbed into newspaper
a), b), d) Inks are absorbed into paper and are not allowed enough drying time, so they are partially wet when delivered
thixotropic
ability of a gel to become more fluid (lower viscosity) with increasing shear and then viscosity increases when shearing stops
viscosity
ability of resisting flow high viscosity: paste ink low viscosity: fluid ink
ink length
ability to be stretched before snapping
oil based drying mechanism
absorption and oxidation
drying mechanisms
absorption, evaporation, oxidation
The best way to improve print quality on rough cardboard is to
apply coating
drying rate is affected by...
area of coverage, relative humidity, ink film thickness, paper absorbency
ink resins
bond the pigments to one another - correct resins determined by intended substrate, printing process
Which of the following statements about ink tack is NOT correct? a) print higher tack ink first, lower tack ink last for better trapping b) high tack ink printed on paper with low surface strength will cause picking c) ink tack relates to offset and screen inks d) ink tack describes how viscous/thick ink is
c), d) Ink tack describes how sticky ink is, not how viscous/thick it is.
folding box board (FBB)
coating, bleached chemical pulp, mechanical pulp, unbleached chemical pulp (good stiffness) e.g. dry foods, tea and coffee, baked goods, etc.
white lined chipboard (WLC)
coating, pulp or white recycled fiber, recycled fiber, mixed recycled fiber, back coating etc. boxes, display outers, food products
basic ingredients of inks
colorant, vehicle, solvent, additives
corrugated board
composed of flutes (waves) and flat (liner) single face: one flute, one liner single wall (double face): one flute, two liners double wall: two flutes, three liners
grain direction of paperboard products (cup)
cracks at the rim of the cup: against the grain grain direction should be perpendicular with height
reel curl
curling from mechanical/physical (bending) force - always curls toward to machine direction - curl side faces the reel at end of paper machine
Which of the following inks are formulated with organic pigment? a) black ink b) golden or silver ink c) white ink d) magenta ink
d)
what type of ink is long ink?
offset printing ink
Which ink were used to print on a brown cardboard box? a) transparent b) opaque
opaque inks (substrate is nonwhite)
Inks can dry by...
oxidation, evaporation, absorption
wavy edge
paper edge grows wavy with increased moisture
laminated/coated paperboard
paperboard coated/laminated with plastic film
solid unbleached sulfate (SUS)
paperboard used where either very high strength (puncture, tear, etc) or high wet strength properties are required e.g. beverage carriers, cereals, shoes, toys, etc.
property of offset ink
pasty
property of screen ink
pasty
flute direction
perpendicular to machine direction; affects structural strength (like fiber direction in paper)
adhesive strength
pick-up strength
colorant types
pigments disperse dyes dissolve
The print on T-shirt cracks after few laundry cycles. What could be added to the ink formulation to avoid this?
plasticizer
UV curing drying mechanism
polymerization (monomers dry when exposed to UV light)
True or false: Thixotropic means the viscosity change of inks are dependent on time
true
True or false: bleach test tests the color strength of inks
true
True or false: ink adhesion is about how well the dry ink film can adhere to the non-absorbent substrates
true
True or false: ink length only relates to paste inks
true
True or false: offset is oil based and long ink
true
True or false: vehicles carry and disperse ink pigments; consists of ink oils, binders, and solvents
true
absorbency of coated vs. uncoated
uncoated has higher absorbency because coated has greater ink hold-out (ink stays on surface)
black pigments
used more than other pigments, more permanent (e.g. furnace black, carbon black)
VOC
volatile organic compound
dimensional stability of corrugated board
when high relative humidity (humid) drops to low (dry), a tight edge forms moisture curl is perpendicular to machine direction
