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Pigments

 
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Introduction  

Nomenclature

Color Index  

Quality  

 

Introduction

Pigments have been used for as long as humans have walked the earth.  Carbon black is most likely the oldest.  It was used to create artwork that adorned many a caveman's humble abode.  We know of three real periods of advancement in pigment development.  The first was the Bronze age, which brought cinnabar for reds, orpiment for bright yellows, lapis lazuli for deep blues, and malachite green.  These wonderful colors were used in the renaissance masters works.

 

The industrial age of the 1800s brought synthetic pigments.  As a chemist, I'm proud of my forefather's work.  These pigments include the chromes (red, green, etc.), lemon yellow, the cadmiums (red, yellow, etc.), alizarin crimson, the cobalt's (green, blue, violet, etc). 

 

The synthetic mineral salts of the 1800's were added to with the organic pigments of the 1900s.  These include the phtalo's, azo's, anthraquinones, quinacridones, and a multitude of other names given to us by IUPAC (chemist org that decides how to name chemicals).  I still get giddy when I end up making one of these pigments in the lab.  Although it seems like chemists love long names, we don't really like to write them, so we make up short common names to use. 

Nomenclature

So what's in a name?  I don't know either.  You'll find that although there is a standard nomenclature, most artist and vendors don't use them.  Typically the common names are used.  Who came up with them?  I'm sure someone knows, but I don't and you probably don't care.  Also, just to confuse you, many of the names on the tubes and their contents don't necessarily match.  I have two tubes of Permanent Green by Winsor and Newton that have different pigments even though their catalogue number is the same.  I suggest you get to know the colors you like by their composition, or at least keep the spent tube until you purchase the new one to make sure that the contents are the same.  As we'll discus later, just because the color of the paint coming out of the tube looks the same, doesn't mean that two paints with different pigments will mix the same with other colors.  I've had this occur in class when students purchase the "same" color from different companies or purchase a "hue" in place of a color.  When the student mixes two colors together they get a different color than the rest of the class.  Sometimes it's pretty surprising.

 

Pigments are either inorganic (minerals or salts) or are organic salts that are not soluble in the vehicle in which they are suspended.

Inorganic pigments are either mineral or are created by chemical processes. Organic pigments  (organic salts) are either created historically from plants or animal remains/excrement or in modern times from chemical processes.  Thank goodness for chemistry otherwise we might be painting with processed cow urine.  The pigment imparts paint characteristics for that color, such as transparency, opacity, tint strength, texture and consistency of the wet paint.

 

Since I just rattled off a few terms, let's define them. 

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Transparency is the ability of a pigment to pass light

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Opacity is the opposite of transparency - the ability of a pigment to cover another paint layer.

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Tint strength is the ability of a pigment to tint white. 

 

Color Index

Pigments are typically used for or from a wide range of sources, objects, inventors, places, etc,.  The ASTM which try to standardize everything in our life from screws to nuclear power plants have tried to make our life easier by standardizing pigment names.  Thus, they gave us the Color Index (CI).  It's essentially the pigment name followed by the color index abbreviation.  You'll find the pigments listed this way on the back of the tubes of paint.

 

Name Abbreviation
Natural Red NR
Pigment Blue PB
Pigment Black PBk
Pigment Brown PBr
Pigment Green PG
Pigment Orange PO
Pigment Violet PV
Pigment White PW
Pigment Yellow PY

 

The CI nomenclature also gives us an idea of how the pigment holds up to exposure to light: Light fastness.

 

Number Rating
I Excellent
II Very Good
III Not Sufficiently

 

Here's some examples of Winsor and Newton paints

 

Name

Pigment(s) Light fastness
cerulean blue PB35 I
Rose Madder Genuine NR9 II
Raw Sienna PY42, PY43 I
Naples Yellow PW1, PW4, PBr24, II
Alizarin Crimson PR83 II
Permanent Alizarin Crimson PR177 I
Yellow Ochre PY43 I
Sap Green PG12, PY100 II
Sap Green PY110, PB15 I
Burnt Sienna PR101 I
     
     

 

 

 

 

Quality

So with the Color Index, it appears that everything is standardized right?  In a perfect world, I'm sure that it is.  The good quality, name brand paints typically have good quality pigments, so there's not a whole lot to worry about.  But, what makes a good quality pigment? Number one is purity. Contaminations of other pigments can grey or dirty the hue of the pigment.  Next is probably, uniformity in the grind of the pigment.  You can think of pigment as rocks that need to be ground up. If they are properly ground, the all of the particles are about the same size.  The fineness of the grind.  To fine, and the pigments can actually change in their color due to the diffraction of light.  Too course of a grind and the pigments may have trouble staying suspended in the paint.  Lucky for us, if we stick with a major brand for either our paint or pigment (if you make your own paints), our pigment should have all the properties we require.

             

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2008, Marc J. Surrency.  Artist scans, images, and web design are protected by copyright. Physical or electronic reproduction in whole or part is unlawful without written permission of the artist.