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52 FLEXOGRAPHY: PRINCIPLES & PRACTICES

sunlight is the most natural way to view

objects, it is not an ideal light source to

judge the color of objects; it is simply too

variable. Artificial light sources are available

and may be controlled and specified to sim-

ulate average, natural daylight, and incan-

descent and fluorescent lamps.

A scale of color temperature, expressed as

degrees Kelvin (°K), is used to quantify light

sources. Various artificial light sources have

color temperatures that range from about

4,000° K to 6,800° K. The D50 CIE Standard

Illuminant has a color temperature of 5,000°

K, representing average natural daylight, and

is the color temperature most widely used in

graphic arts viewing booths. Figure

shows three light sources along with their

spectral curves. The spectral curve shows

the amount of light of the source throughout

the visible range of wavelengths, which is

roughly from 400 to 700 nanometers.

Metamerism

To complicate matters further, there is a

common situation where two objects appear

to have identical color under one specific

light source and then do not match under

other light sources. This phenomenon is

known as metamerism and is caused by use

of different pigment combinations to achieve

the individual color matches. Fortunately, the

metameric condition is both detectable and

controllable.

To avoid metamerism, specific, fixed pig-

ment combinations are used for a given

color match. The problem can be detected

by viewing “matching” objects under differ-

ent light sources. Metamerism can be quan-

tified by spectrophotometric measurements

using different illuminants or simulated

lighting conditions.

COLOR MEASUREMENT

To compare, communicate and store color

data, it is necessary to adopt a measurement

system. The human visual system is the most

discriminating when comparing colors, but it

is neither able to assign numbers to colors,

Color results from the

interaction between

light, an object and the

viewer. The viewer sees

this modified light and

perceives it as a distinct

color. All three ele-

ments, light, object and

viewer, must be present

for color as we know it

to exist.

This diagram shows

three light sources

along with their spectral

curves. The spectral

curve shows the amount

of light of the source

throughout the visible

range of wavelengths

which is roughly from

400 to 700 nanometers.

600–700nm

500–600nm

400–500nm

Light

Source

Object Viewer

Sunlight (D50) Incandescent Light Fluorescent Light (D65)

100

400 500

Perfect daylightObject

Incandescent lights make

objects look redder

Object

Fluorescent lights make

objects look bluer

Object

600 700

100

400 500

600 700

100

400 500

600 700

nor remember them accurately. That is why

some sort of a numerical measurement stan-

dard and an organized method of communi-

cating color is needed.

The pattern of wavelengths that reflects

from an object is the spectral data, which is

often called the “fingerprint.” Spectral mea-

surements can only be taken by using a spec-

trophotometer. The data measured can be

plotted as a spectral curve, providing a graph-

ic representation of the specific color. The x-

axis represents the wavelength of reflected

light in nanometers and the y-axis denotes the

percentage of light reflected. This x-y plot is

the most accurate description of color that

can be achieved. Figure

showed the spec-

trum of the “red” in the rose. Figure

shows

the spectra of a red, green and blue object.

The data from this spectral curve can be used

to calculate the relative coordinates of the

color in the perceptual-based color space

introduced earlier in Figure

Perceptual-based Color Space

CIE – L*C*h° or L*a*b

The next step in color management is to

take the spectral data and express it in a

mode that allows the description of colors

and color differences numerically. The spec-

tral curve of a particular color can be used to

demonstrate the relationship between wave

attributes and the way we perceive these

attributes.

When comparing colors visually, the basic

color or hue difference (h) is seen first; fol-

lowed by the saturation or chroma differ-

ence (C); and last, the lightness or darkness

difference (L). Light waves also have three

attributes that directly affect the perception

of hue, saturation, and lightness. The domi-

nant wavelength of light in the spectral

curve determines the perceived hue of the

color. The wave purity or sharpness of the

peak in the spectral curve, determines satu-

ration. The height (total energy) determines

the lightness.

A numerical color model has been devel-

oped which is intuitive and easy to understand

(Figure

). The L*C*h° system had turned

INK 53

This diagram shows

the spectra of a red,

green and blue object.

Data from the spectral

curve can then be used

to calculate the relative

coordinates of the color

in the perceptual-based

color space.

The L*C*h° system

turns the color space

into a cylindrical model,

and by specifying the

lightness, chroma

and hue values for a

specific color, a unique

numeric description is

generated.

Red

400 500

nm nm nm

600 700

Green

400 500 600 700

100

Blue

400 500 600 700

100

Lightness

100

Chroma

Hue

54 FLEXOGRAPHY: PRINCIPLES & PRACTICES

the color space into a cylindrical model and by

specifying the lightness, chroma and hue val-

ues for a specific color, a unique numeric

description is generated. The L*C*h° numeri-

cal equivalents of the system provide another

method of expressing the coordinates of the

color in the same color space.

Lightness (L): This characteristic of color

describes its luminous intensity-that is, the

degree of “lightness.” Colors can be classi-

fied as light or dark when comparing the L

values (Figure

). For example, when plac-

ing a tomato and a radish side-by-side, the

red of the tomato appears to be much lighter.

In contrast, the radish has a darker red

value.

Chroma (C): The vividness or dullness of a

color describes its chroma. In other words,

chroma indicates how close the color is to

gray or the pure hue. Chroma changes on the

horizontal plane, where the colors in the cen-

ter are gray (dull) and become more saturat-

ed (vivid) as they move toward the perimeter

(Figure

). This color attribute is also

referred to as “saturation.” Again comparing

the tomato to the radish, the tomato is much

more vivid; the radish appears duller.

Hue (h): When asked to identify the color of

an object, the hue is most likely mentioned

first (Figure

). Quite simply, hue is an

object’s perceived color – red, green, orange,

and so on.

Color Tolerancing (CMC). In the L*C*h° color

space, the tolerance for an acceptable color

match is bounded by a three-dimensional

space with varying limits for lightness, hue

and chroma. In the diagram (Figure

), the

variations of the ellipse size throughout the

L*C*h°color space for one particular L value

can be seen. The ellipses in the orange area

are longer and narrower than the ones

across the green area, which appear much

rounder and broader. The ellipses also

change in size and shape as color increases

in chroma. The Color Measurement Com-

mittee (CMC) has provided calculations that

mathematically define an ellipsoid around

each color standard with the three dimen-

sions corresponding to the hue, chroma and

lightness. The ellipsoid represents the range

of acceptance, and automatically varies in

size depending on the position of the color in

the color space. CMC is not a new color

space, but is rather a tolerancing system

within the L*C*h° color space, which pro-

vides good agreement between visual

assessment and instrument measurements.

The eye generally has greater tolerance for

shifts in the lightness (L) dimension of a color

than in the chromaticity (C) or hue (h) dimen-

sions. Therefore, a tolerance ratio of about

2:1 is accepted (the lightness attribute is

weighted twice as much as the hue and chro-

ma attributes.) Though no color tolerancing

Colors can be

classified as light or

dark when comparing

the L values.

Chroma changes on the

horizontal plane, where

the colors in the center

are gray (dull) and

become more saturated

(vivid) as they move

toward the perimeter.

Lightness

100

A is lighter than B

A is cleaner than B

Cleaner

Dirtier

100

system is perfect, the CMC equation best rep-

resents color differences as they are seen. It is

becoming a recognized industry standard. A

color difference between two objects on the

CMC L*C*h° scale is expressed as a total

color difference and is referred to as – delta E

CMC 2:1. A delta E value of 1 is an approxi-

mation representing a color difference just

detectable by the average human observer.

The diagram (Figure

) shows typical num-

bers generated by color computer software

when checking “Bob’s rippled chips” bags

The color difference of 2.36 CMC 2:1 is readi-

ly seen by the trained eye and may be unac-

ceptable.

It should be pointed out that many presses

cannot maintain better than 2 ∆E CMC 2:1,

hence the need to constantly “tweak” the ink

or the press settings. A word of caution: The

color computer is only a tool that assists with

achieving acceptable color; it should never

be allowed to overrule the trained eye. If the

measuring instruments are not used proper-

ly, under the correct conditions they will not

output useful information, and even then the

information must be interpreted by the user.

INSTRUMENTS

In most cases, the instrument used to mea-

sure color is only accurate when it has been

calibrated. Most instruments require a “warm-

ing up” period before the readings are stable

and the instrument calibration should be reg-

ularly checked against a color standard.

Densitometer

The densitometer is the least sophisticated

color control instruments in design and, gen-

erally, the least costly. The main design

incorporates the use of three- or four-col-

ored filters. Each filter color, (red, green,

blue) allows approximately one third of the

visual spectrum of light to pass through and

reach a photo-detector. By analyzing the

combination of signals from the light trans-

INK 55

Color plotted in this

manner provides a

subjective desciption

of a color.

The Color Measurement

Committee (CMC) has

provided calculations

that mathematically

define an ellipsoid

around each color stan-

dard with the three

dimensions correspond-

ing to the hue, chroma

and lightness. The ellip-

soid represents the

range of acceptance,

and automatically varies

in size depending on the

position of the color in

the color space.

The diagram shows

typical numbers

generated by color

computer software

when checking a print

sample. The color

difference readily seen

by the trained eye

may be unacceptable.

A is bluer than B

270

180

BOB’S

Rippled

Chips

BOB’S

Rippled

Chips

Lightness

Color difference (CMC 2:1) of 2.36

Std

L 51.11

C 64.48

H 28.92

Test

L 52.89

C 61.17

H 26.95

100

CMC = Color Measurement Committee

• Color perception is elliptical

• An ellipsoid represents volume of color acceptance

• Ellipses vary throughout color space

• Notice red/green differences

The color difference shown here is for illustration only and will differ from the

value of 2.36 quoted due to the variability of the printing process.

56 FLEXOGRAPHY: PRINCIPLES & PRACTICES

mitted through the colored filters, the den-

sitometer can determine some of the attrib-

utes of the color being measured.

A densitometer is able to compare color,

but not in the same manner as the human

eye. Densitometers vary widely in the num-

ber of functions that they perform, but the

main function of a densitometer is to mea-

sure density. This value correlates very well

to ink-film thickness and is used to calculate

other print attributes, such as hue error,

grayness and tone reproduction in process

printing.

Colorimeters

For capabilities beyond those of the densi-

tiometer, colorimeters are the basic color

measuring tools. Two types of colorimeters

are available on the market today: tristimu-

lus and spectral-based.

Tristimulus. The tristimulus colorimeter is

very similar in design to the densitometer. It

has red, green and blue filters that are used

to split the visible spectrum into thirds. The

primary differences in the tristimulus col-

orimeter is two-fold. First, the tristimulus

colorimeter is engineered to see color like

the human eye, whereas the densitometer is

equipped with specific sensitivities for

process-ink colors. Second, the micro-

processor in the tristimulus instrument

works with very different numbers and algo-

rithms. Colorimetric formulas generally

yield three numbers that allow the user to

plot the measured color as a point in a three-

dimensional space.

Spectral. A spectral-based colorimeter, or

spectrocolorimeter, divides the visible spec-

trum into very narrow segments, each repre-

senting only a very small and select portion

(bandwidth) of the spectrum. Because it

divides the spectrum into many parts, a

spectrocolorimeter can gather more infor-

mation and is more accurate than a tristimu-

lus colorimeter or densitometer. Conse-

quently, these spectral devices have greater

repeatability and inter-instrument agree-

ment; therefore, they carry a higher price tag

than the more simple designs. As with the

tristimulus unit, the spectral-based instru-

ment presents the color measurement as the

same three L*C*h° (L*a*b) numbers.

Increased sensitivity to slight color differ-

ences makes the colorimeter a very useful

tool for testing incoming inks and sub-

strates. Colorimeters also find use in pro-

duction departments where corporate col-

ors or special matches are printed and com-

pared to a standard.

Spectrophotometers

Spectrophotometers work in a similar way

to spectral-based colorimeters. They split the

visible spectrum into very small segments

using either narrow-band filters or a diffrac-

tion grating. All spectrophotometers can out-

put the same data as colorimeters, however,

the spectrophotometer is a more sophisticat-

ed instrument and able to output the infor-

mation as a spectral curve. This curve is

derived from taking the percentage reflec-

tance at each wavelength measured and plot-

ting it on a graph. Once each point has been

plotted, the dots are connected to produce a

curve that is unique to each pigment color

measured. These curves can be used like a

fingerprint to identify the pigments that

make up an ink.

The spectrophotometer is the ideal instru-

ment to use when mixing inks. The instru-

ment can save a great deal of time spent on

hit-and-miss ink mixing. Its use will improve

the batch-to-batch consistency of ink, along

with ensuring consistency between different

ink department individuals.

COLOR-MATCHING THEORY

The most useful visual tool in color

matching is the color wheel (Figure

), a

slice of L*C*h° color space. The colors of

the spectrum are arranged in a circle as

shown in the diagram, reducing chroma to

black at the center. When color matching,

this wheel should be kept in mind. Mixing

pigments which are adjacent on the color

wheel results in colors that are clean or

bright. For instance, if green-shade cyan

(GC blue) is mixed with green-shade yellow

(GS yellow) the mixture will be a clean,

bright green.

Drawing a line on the color wheel

between the two pigments shows how close

to the center gray area the line will travel. If

the same GC blue is mixed with red-shade

(RS) yellow on the opposite side of the

color wheel, the line on the color wheel join-

ing the two pigments travels closer to the

center gray area and the mixed ink will be a

dull, dirty olive-green.

The concept here is that when color match-

ing, the ingredients should be kept close in

the color wheel to obtain clean, bright color

matches and further apart to “dirty up” the

match. It is important that color-match for-

mulas are constructed with individual pig-

ments that are not too far apart. For exam-

ple, a brown should not be matched using

red, yellow and blue, preferably it should be

matched with red, yellow and black (the cen-

ter point on the wheel). Formulas containing

several pigments from distant areas of the

color wheel will change hue very quickly

with small viscosity changes.

It is critical to be able to talk about color in

a way that is intuitively understood. One way

is to use the color wheel and remember the

position of individual colors on the wheel. In

this way, when the hue of a batch of red ink

is compared against the standard red ink, the

batch may be more yellow or more blue in

hue than the standard (Figure

). If the

batch is identical in hue it may, for example,

be too strong or too dark. If this is the case, it

would have a lower L value than

the stan-

dard. An addition of extender or solvent to

the batch would correct this.

As the ink is weakened, all three color

attributes (L*C*h°) are affected at the same

time (Figure

). This chart summarizes

what happens to the L*C*h° numbers as var-

ious colors of ink are weakened. It should be

noted that the ink can be weakened by

adding solvent, by adding extender or by use

of a lower-volume anilox roller.

COLOR-MATCHING PROCEDURE

A general flowchart for mixing a special

color ink is shown in Figure

. It shows the

procedure for making a small, 100-gram

batch to test and develop the specific formu-

la. End-use requirements may dictate the

choice of pigments available for a particular

color formulation. Any colors that might be

a problem, such as small amounts of rho-

INK 57

The most useful visual

aid in color matching is

the color wheel, a slice

of L*C*h° color space.

When the hue of a batch

of red ink is compared

against the standard red

ink, the batch may be

more yellow or more

blue in hue than the

standard, as is indicated

on this color wheel.

RS Yellow

Orange

GS Yellow

GS Blue

Yellows can be red or green to the standard

Blues can be red or green to the standard

Greens can be yellow or blue to the standard

Reds can be yellow or blue to the standard

Oranges can be yellow or red to the standard

58 FLEXOGRAPHY: PRINCIPLES & PRACTICES

damine pigment in a white tint, should be

avoided. The combination of rhodamine and

titanium dioxide is unstable due to chemical

reactivity.

If fade-resistance or outside exposure are

required, the pigments chosen should be

suitable. When specified by the end-use

requirements, the pigments used should be

stable to aggressive products such as milk,

acids, alkalis, oils and solvents. Finally, the

lowest cost combination of pigments should

be used to achieve the color. Once the small

test batch is made, the amount of material

can be scaled up for the press run quantity.

The initial formula can be obtained from a

variety of sources: historical data, experi-

ence (especially for similar colors), or com-

puter formulation software.

1. Weigh Sample. A 100-gram sample of the

initial formulation is weighed in the ink

laboratory. Pigment selection is based on

the color being matched using the color

wheel as a guideline. There are other

considerations for the optimum color

match. Use the fewest number of colors

in the match since this makes weighing

and control of the ink for the press much

simpler and easier to adjust and control.

2. Adjust Viscosity and Strength. This step is

based very much on experience and

knowledge of both the ink system and

the press where it will be used. Actual

This chart summarizes

what happens to the

L*C*h° numbers as var-

ious colors of ink are

weakened. It should be

noted that the ink can

be weakened by adding

solvent, by adding

extender or by use of a

lower-volume anilox

roller.

A general flowchart for

mixing a special color

ink shows the procedure

for making a small,

100-gram batch to test

and develop the specific

formula.

Weigh up

100 grams

Adjust

viscosity and

strength

Proof

Visual and

Spectral

Measurement

Color OK?

Approval

Process

Yes

Black

White

Green

Purple

Blue

Rhodamine

BS Red

YS Red

Orange

GS Yellow

Extender

Adjust

formula

L Value will: C Value will: H Value will:

Go lighter

to a higher number

Yellows

Go dirtier

to a lower number

Go greener

to a higher number

Go lighter

to a higher number

Oranges

Go dirtier

to a lower number

Go yellower

to a higher number

Go lighter

to a higher number

Reds

Go dirtier

to a lower number

Go bluer

to a lower number

Go lighter

to a higher number

Blues

Go dirtier

to a lower number

Go greener

to a lower number

Go lighter

to a higher number

Greens

Go dirtier

to a lower number

Stay about the same

pigment concentration and the ink film

thickness which the press inking sys-

tem will lay down govern this step. Any

changes to the ink system or the press,

must be conveyed to the color matcher-

an obvious statement but a frequently

violated procedure.

3. Proof. A draw-down is made using a

method that matches the coating weight

and appearance of the actual press. The

substrate used for proofing should be

the one that will be used in production.

If the ink is to be reverse-printed on film

and backed with white ink, it should be

proofed this way. If the ink is to be print-

ed on coated board and UV-lacquered,

once again it should be proofed this way.

4. Inspection. Does the proof match the

color target ? This is where the skills and

experience of the color matcher are

demonstrated. The proof sample is com-

pared to the color standard approved by

the end user. While the final decision is

made using a visual comparison, spec-

trophotometric measurements are a

useful tool to aid the color matcher. The

most difficult task is to match a color

standard that has been printed by a

process other than flexo and/or on a dif-

ferent substrate. A typical scenario is

where an ink for printing on film is being

matched to a spot color, which is print-

ed offset-litho on paper. When the ink

color technician is satisfied with the

match, it can be measured and stored in

the color computer.

5. Approval Process. Color-match proofs

are sent to the customer for approval

and copies are retained in the inkroom.

Signed, approved proofs from the cus-

tomer then serve as the color target for

making ink for the qualifying pressrun.

PROOFING METHODS

As indicated earlier, the main requirement

of a proofing method is that it lay down the

same amount of ink as the press and also

match the press print appearance in terms of

uniformity. There are many proofing meth-

ods used for flexo printing. They range from

a simple blade draw-down on paper, to actu-

al flexo printing on a pilot scale press. On

the one hand, the blade draw-down may be

too crude for many applications, and at the

other end of the scale, the pilot press too

expensive and time consuming. Three com-

monly used proofing methods, which are

quick and accurate, will be reviewed here:

the flexo hand proofer, the automated bar

proofer and the laboratory flexo proofing

machine.

Flexo Hand Proofer

This proofing device consists of a rubber

roller and anilox roller mounted in a frame.

The ink is dripped into the nip formed by

these two rollers, and the draw-down is

made by running the roller over the substrate

at even speed and pressure (Figure

There is some variability in the flexo hand

proofer, mainly caused by operator differ-

ences in speed and pressure used during the

draw-down. Less pressure and more speed

transfers more ink.

The inherent amount of ink transferred

can be changed by changing the anilox roller

INK 59

The flexo hand proofer

consists of a rubber

roller and anilox roller

mounted in a frame.

The ink is dripped into

the nip formed by these

two rollers, and the

draw-down is made by

running the roller over

the substrate at even

speed and pressure.

Rubber Roll

Anilox Roll

Line 200

Line 400

Cell

Volume

5.0

Cell

Volume

10.0

60 FLEXOGRAPHY: PRINCIPLES & PRACTICES

volume and by using rubber rollers of hard-

er or softer durometer. Many inkrooms use

several flexo hand proofers of various ink

delivery rates to correlate with individual

presses or even specific decks within a

press. The flexo hand proofer is capable of

laying down ink films which match the press

in terms of appearance, even on substrates

which are uneven.

Bar Proofer

The bar proofer is a mechanically driven

device where speed and pressure are con-

trolled and reproducible. The results from

this device are not operator dependent. A

wire-wound rod draws ink down on the sub-

strate (Figure

). The amount of ink that is

deposited is dependent on the thickness of

the wire on the rod; thicker wire lays down

more ink. Different coating rods, or proofing

bars, are used to correlate with specific

press conditions. The main disadvantage of

this method of proofing is that the proofing

bars are not able to lay down ink as smooth-

ly as the press on uneven substrates.

Laboratory Flexo Proofing Machine

This machine generally has a detachable

printing wheel about 7” in diameter on which

a photopolymer plate is mounted in a typical

way (Figure

). The machine also has a

detachable anilox roll and a doctor-blade sys-

tem. A full range of anilox rolls are available

to suite the actual press configuration.

The substrate sample is mounted on a

rigid carrier and placed on the transport

guide. Printing speed, anilox pressure and

printing pressure are selected according to

the press application.

A sample of ink is applied to the nip

between doctor blade and anilox and the

machine is started. The automatic cycle

brings the anilox roll in contact with the

print wheel which in turn contacts the sam-

ple. The print wheel makes one rotation,

printing the substrate and proofing the sam-

ple ink in a very controlled manner.

The bar proofer is a

mechanically driven

device where speed and

pressure are controlled

and reproducible.

A laboratory flexo

proofing machine

brings the anilox roll in

contact with the print

wheel, which in turn

contacts the sample.

This automatic cycle

makes printing the

substrate and proofing

the sample ink a

controlled process.

Proofing Bars Anilox Roll

Line 200

Line 400

Cell

Volume

5.0

Heavy

Light

Cell

Volume

10.0

Detachable

Plate Wheel

Transport Guide

Substrate

Carrier

Printing Plate

Caliper Range

0.045" to 0.250"

Doctor

Blade

Ink Sample

Detachable

Interchangeable

Anilox Roll

Authenticating the Proofing System

A simple experiment may be conducted to

verify that the inkroom proofing method cor-

relates with the press. From a press that is

printing efficiently, collect: a sample of ink

from the ink reservoir, some unprinted stock

and a newly printed sample. Proof the ink

sample on the unprinted stock with the nor-

mal proofing method and compare it to the

press sample, preferably using a spectropho-

tometer. If the L (lightness) value difference

is less than 0.5 units, the correlation is

acceptable. If not, the proofing method

should be adjusted until the L value is with-

in 0.5 units. The value of 0.5 units in lightness

is used as a guide only and may vary for dif-

ferent processes and customer require-

ments. Future releases of FIRST (Flexo-

graphic Image Reproduction Specifications

& Tolerances) will address the issue of cor-

relation of proof to press.

INK-ASSEMBLY OPTIONS

Inks supplied from the ink company are

available in several different physical forms,

each of which has distinct advantages and

disadvantages. Some converting plants have

a diverse product range, sometimes involving

printing on both films and paper, requiring

several different ink systems to meet all

applications and end-use specifications. Here

is a review of ink assembly options available.

Pigmented Bases and

Blend Varnishes

In this option, the ink company manufac-

tures and supplies the printer with about 10

highly pigmented bases in a base resin. Each

of these bases contains a single pigment,

such as cyan blue, OT yellow or titanium

dioxide. The printer then mixes the pigment-

ed bases together with a blend varnish to

formulate the color and quantity of ink for a

specific need.

A proven example of a pigmented base can

be seen in nitrocellulose-ink formulation.

Most colors in the PMS book may be repro-

duced by blending 10 nitrocellulose bases

together with an appropriate blend varnish.

The formula for a nitrocellulose gloss, green

ink, formulated for film printing, blended

from pigmented bases would look like this:

nitrocellulose cyan blue base 10%

nitrocellulose OT yellow base 40%

gloss, film, blend varnish 50%

There are several advantages to this ink-

assembly method. The ink strength may be

increased or decreased by raising or lower-

ing the amount of pigmented base in the ink.

The ink can be formulated for other end-use

applications; for example, where heat resis-

tance is needed, a heat-resistant blend var-

nish is substituted for the gloss-blend var-

nish. Low inventories and quick response

times are possible when blending inks from

bases and blend varnishes. When this

method is adopted by the converter, more

responsibility for testing the finished ink for

end-use properties is moved from the ink

company to the in-house blending system.

Use of the wrong blend varnish could obvi-

ously have drastic effects on the converted

product. It should be noted that similar

water-based blending systems are available,

many of which are based on acrylic resins.

Single Pigment Finished Inks

The ink company supplies the converter

with about 10 single-pigment finished inks.

When matching colors, the specified color is

blended from this range of finished inks, and

the matched colors and inks are used for a

specific end-use application. For example,

the formula for a nitrocellulose gloss, film,

green ink, blended from single pigment fin-

ished inks would look like this:

gloss film cyan blue ink 20%

gloss film OT yellow ink 80%

Any gloss film job can be accommodated

INK 61