Coatings Technology Handbook Episode 3 Part 8 doc

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the paint that forms a film. A synonym for vehicle is binder. Vehicles come in many types. The types that
will be discussed in this chapter include oil, tempera (based on egg yolks), watercolor (based on gums,
sugar, and starch), alkyd (normally a polyester), and latex (plural is latices, chemically these are emulsions).
Artist’s colors are generally sold in two grades: professional and student. The professional grade is
generally used by those who make a living by producing and selling their artwork. The student grade is
intended for use by students who aspire to a career in art.
There are many differences between the two grades. The professional grade generally contains high
percentages of pure color (pigment). Student grade is normally characterized by lower percentages of
color. Very often, student grade does not contain the “pure color” that is listed on the label. In this case,
the word “HUE” appears on the label. This means that a single pigment or combination of pigments is
being employed to approximate the “pure color.” Very often, the “pure color” is very expensive, while the
hue is cheaper. In addition, the hue rarely has the brilliance of the “pure color.” A further difference is
that the student grade often contains extender pigments to help reduce cost while still maintaining the
consistency (artist term for this is “feel”) of the professional grade.
Artist’s colors are produced in a number of vehicle systems. As vehicle systems evolved, so did pigments.
This chapter will outline historical development of vehicles and enumerate their compositions. Con-
jointly, this time-line formulary will contain the pigments associated with the system at discovery time.
It will also list those pigments in use today, as well as what they replaced. Discovery dates of pigments,
as well as the approximate date of first usage in artist’s colors, will also be listed.
The very first artist’s color created by prehistoric man was a black made from charcoal. This was used
for drawing. There was no binder involved — just pure charcoal put onto surfaces such as rocks, cave
walls, and hides. Soon after charcoal came into use, early man began using mud, which was available in
various colors. These muds were various shades of natural iron oxide pigments (yellow, red, and brown)

and were applied directly to cave walls. As was the case with charcoal, no binder was involved, just pure
color. These muds were derived from riverbanks, lakefronts, and other similar places. They were used to
create the now celebrated Cro-Magnon cave paintings. The paintings were of stick figures. They were
thin lines of mud smeared across a cave wall in the form of a recognizable animal or human shape. Art
stayed at this stage until the ancient Egyptians invented watercolor.
Watercolor came into prominence around 4700 B.C. in ancient Egypt. For the most part, watercolor
is based on a transparent pigment system. The background of a brilliant white comes from the paper,
which is used as the substrate. It is utilized to make white and light tints. Pigmentation consists of both
transparent and nontransparent colors. The nontransparent colors are applied in an extremely diluted
state. These colors are diluted to the point where they are almost as brilliant as the transparent colors.
There is an alternate pigment system that employs white pigment as an opacifier. The choice of pigment
system, whether in ancient times or today, has always been left to the artist. Neither system is wrong nor
better. The choice depends on the desired artistic effect.
The palette (pigment choice) available in ancient Egypt for use in watercolor included a host of
list is set up by color type. This is then broken down to individual colors designated by color title and
composition.
The composition of the vehicle used to make watercolor is basically unchanged from ancient times.
The major ingredients used by the Egyptians were gum arabic (a product of Somalia), water, sugar syrup,
glycerin, dried extract of ox bile, and dextrin, which is derived from white potatoes. Some more modern
formulae replace the sugar syrup with pure glucose. The ox bile can be replaced with modern wetting
agents of the type generally associated with latex house paint production. The ancient Egyptians had no
need to use a preservative, because arid conditions in Egypt produced an atmosphere in which bacteria
could not survive.
There is a system of similar composition called Gouache (pronounced GWASH). This system uses the
same vehicle but employs opaque colors, usually with extender pigment added to increase dry opacity.
Both systems employ the same pigmentation types.

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pigments known from the dawn of recorded history. Table 117.1 lists colors used by the Egyptians. The

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Now let us turn our attention to oil color. Oil color, which was invented in the year 1400 A.D., originally
had a palette that was very similar to that of the ancient watercolor palette. The most noticeable exception
is the addition of a white color called Flake White (basic lead carbonate). Technology to make basic lead
carbonate dates back to the days of ancient Rome. Another color, which, if it did not exist in the year
1400, was available shortly thereafter, is Naples Yellow. In its original form, Naples Yellow was lead
antimoniate. Today, it is made as a hue from a combination of Cadmium Yellow, zinc oxide and Ochre
(Natural Yellow iron oxide).
As time went on, the modern palette evolved to the point where it matched the modern watercolor
palette with the exceptions noted above. The composition of oil color is fairly simple. Generally, only
three items are used in an oil color formula. They are the colored pigment, the oil (usually alkali refined
linseed oil) and a stabilizer (normally aluminum stearate). Over the years, different grades of oil have
been used to make oil color. In the beginning of the 15th century, only raw linseed oil was available.
Soon afterward, purification by heating was discovered. At the same time, people learned how to make
“sun-bleached linseed oil.” This is made by mixing linseed oil with water and exposing the mix to sunlight.
The water acts to remove impurities in the oil, while the sun bleaches and lightens the oil. After a few
weeks or months of exposure, the oil is separated from the water and then used. In later years, oil made
by this technique was called “superior linseed oil.” By the 17th century, both stand oil and refined linseed
oil were in common use. Stand oil is partially polymerized linseed oil. The oil is polymerized by heating
it to 550 ± 25˚F and maintaining that temperature for a few hours. This causes the viscosity to increase
significantly. A number of other effects can also be seen. These include the excellent leveling and gloss.
Upon aging in dry films, stand oil shows much less yellowing than regular linseed oil. Less polymerization
occurs during drying, because it is partially polymerized during the heating process. This, in turn, leads
to less yellowing.

Originally, refined linseed oil was refined by an acid process. The mechanism called for acid (usually
sulfuric acid) and water to be added to the oil. This removes impurities and lightens color. The best
grades have all the water and acid removed before packaging. While acid refined linseed oil is still available,
it has, for the most part, been replaced by alkali refined linseed oil. Here, a strong alkali replaces the acid.
The use of alkali to refine linseed oil often removes more impurities and provides better color than would
be seen with the use of acid as the refining agent.
Occasionally, other types of oil are used in the formulation of artist’s colors. The most notable of these
is poppyseed oil. It is used mainly in whites, because it is naturally colorless. This makes a white paint
made from it appear “whiter” than paint made from amber-colored linseed oil. Less frequently, walnut
oil is used as a linseed oil replacement. Walnut oil has the same clarity as poppyseed oil, but, upon aging,
it can turn rancid and give off a strong odor. While the paint is perfectly useable, the perception of quality
is totally ruined.
Well-formulated oil-based paint dries to a glossy, durable finish. The pigment volume concentration
(PVC) is low, especially when compared to other types of artist’s colors. A good example of this is tempera
paints. Tempera and oil color were invented at the same time, but, due to tempera’s radically different
composition, it dries to a flat finish. The finish is due to the high PVC of the paint. The high PVC is a
result of the tempera vehicle. Tempera paint was the first emulsion paint ever created. This emulsion is
a naturally occurring phenomenon. The basis of tempera is egg yolk. The yolk contains a water solution
of albumin, a nondrying oil called egg oil, and lecithin. Each ingredient has its own function. The albumin
is a binder. When heated, albumin will coagulate to form a tough, insoluble permanent film. A cooked
egg is an example of this coagulation. Likewise, when albumin is diluted with water and spread out in a
thin film to be dried by sunlight, it coagulates to form a film. The egg oil acts as a plasticizer, and the
lecithin is an excellent emulsifier. All that is needed to create a tempera paint from the yolk is pigment
and water. Over the years, egg yolks were replaced with other substances to form alternate tempera paints.
These emulsions are based on any of the following: gum arabic, wax, casein, and oil. All have some degree
of acceptance.
After the acceptance of oil and tempera colors in the 15th century, creativity to develop new vehicles
fell into a dark age. Yes, pigments did continue to develop. However, vehicles did not. The next few

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Artist’s Paints: Their Composition and History

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changes in vehicle technology came in the 1920s. Two developments occurred simultaneously. These were
the invention of the alkyd resin and the development of latex emulsions. The original alkyds were made
by the reaction of glycerol (a polyhydric alcohol) with phthalic anhydride (a polybasic acid) in an oil
medium. In time, glycerol was replaced by pentaerythritol (penta imparts greater flexibility and color
stability to the resin). Alkyds were originally used in industrial and house paint systems. However, around
1960, some manufacturers of artist’s paints began to partially replace linseed oil in selected colors. Full
product lines based upon alkyd resin technology did not appear until the late 1970s/early 1980s. Today,
almost every artist’s paint producer has a full line of alkyd colors.
In the late 1920s, latex emulsion technology was also emerging. The original latices were made from
styrene-butadiene. These were very poor in quality. Sometimes the emulsion would break. Sometimes
reactions after processing occurred. These reactions included gelation and seeding of the emulsion. In
the 1930s, resin producers began using methylmethacrylate as a basis for emulsions. By the end of World
War II, latex emulsions were being used in house paint formulae. By 1952, boutique art shops began
carrying a line of latex (now called acrylic) colors. The name change was the result of the switch from
styrene-butadiene to methylmethacrylate. By 1960, all major manufacturers had complete lines of acrylic
colors. The color palette for acrylic colors is the same as the palette for watercolor. There is no Flake
White (basic lead carbonate) or zinc oxide due to the reactivity of these pigments with the latex.
The last advance in artist’s paint technology came in 1993, with the advent of water-thinnable linseed
oil paint. As stated earlier, water-thinnable linseed oil paint was created by dismissing the old myth that
water and oil did not mix. Chemists were able to do this alteration of linseed oil. Linseed oil is a composite
of between 17 to 21 different fatty acids. The number varies with the source of the oil, as is the case with
most naturally occurring materials. All of these fatty acids are at varying percentage levels in the oil.

Some of these acids are hydrophobic, while some are hydrophilic. By adding more of the hydrophilic
acids, an oil that will accept water by forming a temporary emulsion is made. The beauty of water-
thinnable oil colors is that they eliminate the need for solvents by serving as both thinner and cleanup
agent. This greatly reduces studio toxicity. If, however, one wishes to use the solvents that have been used
since the 15th century, the system will accept them. The palette that is in use for water-thinnable oil
colors is the same as the palette for conventional oil color.
composition of the pigment, the date of discovery, the date of first usage in artist’s colors, and the pigment
replaced. This table refers only to pigment. Vehicle type has been deleted. All colors listed are available
in all vehicle types described herein, with very few exceptions. In the discovery and first usage columns,
the notation “Ant” means that the discovery or first usage goes back into antiquity.
Hopefully, this gives the reader an overview of the history and composition of artist’s paints.

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Ta ble 117.2 summarizes the modern palette. Listed are the artist’s name for a color, the chemical

Artist’s Paints: Their Composition and History

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Naples Yellow Hue Mixture of zinc oxide,
Cadmium Yellow, and
Ye l l o w Oxide
Not Applic. 1920s Lead antimoniate (known
since the 1500s)
Phthalocyanine Blue A 16-member ring comprised
of four isoindole groups
connected by four nitrogen

atoms; in the center of the
ring is a copper atom
1935 1936 Prussian Blue (ferric-
ferrocyanide) discovered
in 1704 and introduced in
1724
Phthalocyanine Green Same as Phthalocyanine Blue
but four chlorine atoms are
added to each isoindole
group
1938 1938 None
Quinacridone Colors
1. Red (Yellow shade) Gamma trans-linear
Quinacridone
1955 1962 None
2. Red (Blue shade) Gamma trans-linear
Quinacridone
1955 1962 None
3. Violet Beta trans-linear
quinacridone
1955 1962 None
4. Magenta Disulfonated trans-linear
Quinacridone
1955 1962 None
Raw Sienna A natural earth composed
mainly of hydrous silicates
and oxides of iron and
aluminum
Ant. Ant. None
Raw Umber A natural earth composed

mainly of hydrous silicates
and oxides of iron and
manganese
Ant. Ant. None
Strontium Yellow Strontium chromate 1836 1950 None
Titanium White Mainly titanium dioxide
~60% with some zinc oxide
and/or barium sulfate ~40%
combined
1870 1920 Flake White (basic lead
carbonate) known since
antiquity
Ultramarine Colors
1. Blue
2. Green
3. Red
4. Violet
All are complex silicates of
sodium and aluminum with
sulfer. The degree of
sulfonization determines the
color
1828 1828 Ground gemstone
Lapis lazuli
Ve r million Mercuric sulfide Ant. 8th century Cinnibar, an ore with
mercuric sulfide in it
Viridian Hydrous chromic oxide 1838 1862 None
Ye llow Ochre A mixture of synthetic
hydrous iron oxide with
alumina and silica

19th century 19th century Natural version of the same
mixture. It dates into
antiquity
Zinc White Zinc oxide About 1820 1834 in
watercolor;
1900 in oil
color
Chalk (calcium carbonate)
Flake White (basic lead
carbonate)

Source:

Lewis, Peter A.,

Federation Series on Coatings Technology-Organic Pigments,

3rd ed., revised September 2000. Mayer,
Ralph,

The Artist’s Handbook of Materials and Techniques,

3rd ed., revised 1970.

TA BLE 117.2

The Modern Palette

(Continued)

Artist’s Name Chemical Composition Discovery Date
First Used
Date Pigment Replaced

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118

Fade Resistance of
Lithographic Inks —
A New Path Forward:
Real World Exposures in
Florida and Arizona
Compared to
Accelerated Xenon Arc

Exposures

118.1 Florida and Arizona Outdoor under Glass
Exposures

118-

2

118.2 Accelerated Xenon Arc Exposures

118-

5

118.3

How long will an ink remain fade resistant under the variety of lighting conditions that it may encounter
during its service life? What is the cost of product failure? What is the price/performance trade-off between
affordability and performance? Is there a quick method to determine which ink is best for a specific
application? This paper answers these questions and provides a useful roadmap for assessing ink durability.
First, results are presented from real world sunlight through window glass exposures in Florida and
Arizona. These internationally recognized test locations provide a “worst case” scenario by exposing inks
to high ultraviolet (UV), high temperatures, and high relative humidity (RH).
Second, test results are presented from laboratory xenon arc exposures performed on an identical set
of lithographic ink specimens. The purpose was twofold: (1) How well do laboratory xenon exposures
correlate with Florida and Arizona exposures in terms of actual degradation and relative rank order? (2)
How much faster are the accelerated laboratory exposures compared to the natural exposures?
This definitive study correlates real world and accelerated laboratory test results for lithographic inks.

Eric T. Everett

Q-Panel Lab Products

John Lind

Graphic Arts Technical Foundation
(GATF)

John Stack

National Institute for Occupational
Safety & Health/National Personal
Protective Technology Laboratory

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Test Program • Effect of Seasonal Variation • Arizona
Exposure
Conclusions 118-9
Compared to Florida Outdoor under Glass Exposure
Why Xenon Arc Testing? • The Test Program • Xenon Arc
Further Reading
118-10
Test Results • Relative Humidity • Xenon Arc Exposure

Fade Resistance of Lithographic Inks

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FIGURE 118.2

GATF technical staff selected eight representative lithographic ink colors printed on a standard
substrate for fade resistance testing.

FIGURE 118.3

Ink specimens were placed in ASTM G24 glass-covered exposure racks in Florida and Arizona
benchmark locations.

TA BLE 118.1

Total Sunlight Outdoor

Exposure Summary MJ/m

2

at 300 to 3000 nm

Exposure Days MJ/m

2



Florida fall 90 1926.17
Florida winter 90 1541.13
Florida spring 90 1252.54
Florida summer 90 1081.73
Arizona fall 90 1611.20

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However, by 35 d, the inks exhibited a wide range of fade resistance, from excellent to poor. Therefore,
35 d was chosen to evaluate the performance of the inks in the various outdoor exposures.
Figure 118.5 shows the range of durability for the three Yellow ink test specimens in the Florida fall
exposure. Despite being the same color, the three Yellow inks had significant differences in their fade
resistance. Yellow A performed dramatically better than Yellow B or Yellow C. This is because Yellow A
is fade resistant and suitable for fine art reproductions or outdoor applications, while Yellow B and C
are intended for general commercial printing.

FIGURE 118.4

Fade resistance range for eight colors.

FIGURE 118.5

Fade resistance range for one color.

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Coatings Technology Handbook, Third Edition

FIGURE 118.7

Fade resistance correlation for Florida: winter vs. summer.

FIGURE 118.8

Fade resistance correlation: Florida: vs. Arizona.

TA BLE 118.2

Rank Order Correlation Matrix

Florida Summer Florida Fall Florida Winter Florida Spring Arizona Fall

Florida Summer — 0.98 0.93 0.98 0.90
Florida Fall 0.98 — 1.0 0.95 0.98
Florida Winter 0.93 1.0 — 0.97 0.96
Florida Spring 0.98 0.95 0.97 — 0.93
Arizona Fall 0.90 0.98 0.96 0.93 —

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FIGURE 118.10

GATF and Q-Lab tested inks in Q-Sun Xenon Test Chambers.

TA BLE 118.3

Xenon Arc Exposure Test Conditions

Q-Sun Xenon (Xe-1 and Xe-3H)
ASTM D3424, Method 3
Window Glass Filter
Irradiance Level: 0.55 W/m

2

/nm at 340 nm
RH: Xe-1 Effective RH = 15%
Xe-3 RH = 50%
Exposure Cycle: Continuous Light at 63

±

3

°

C (145

±

5

°

F)
Test Duration: 31 d
Total Radiant Exposure = 1473 kJ/m

2

at 340 nm

FIGURE 118.11

Q-Sun fade resistance range.

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Fade Resistance of Lithographic Inks

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Bugner, Douglas, Joseph LaBarca et. al, “Survey of Environmental Conditions Relative to Display of
Photographs in Consumer Homes,”

IS&T Publications

, 2003.
Lucas, Julie, “Keep Your True Colors: Lightfastness and Weathering Testing,”

GATF World

, May/June 2001.
To bias, Russell H. and Eric T. Everett, “Lightfastness Studies of Water-Based Inkjet Inks on Coated and
Uncoated Papers,”

IS&T Publications

, 2002.

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