A Basic Primer on Watercolor Pigments, pt. 1


In anticipation of my upcoming mini-workshop on "Exploring Color for Watercolorists" (a shameless plug if there ever was one!), I've been writing up this primer.  Students will get it all next week, of course, at the class, but over the next few weeks I'll also be sharing it all with you here as well.

This primer is meant as a tool to help fellow artists understand some of the basic physical properties of watercolor pigments and how they are labeled for purchase, with the goal of creating more informed buyers and painters.  The way watercolor paints are physically constituted affects the way they act, both when wet and when dry.  It’s mildly technical, but this can be very helpful knowledge when we paint with them and, of course, when we buy them!

I’ve broken things down into three sections.  The first is a basic introduction to the physical properties of pigments.  The second goes over labeling practices so we can decode what we are buying!  And the third section features my personal opinions on purchasing paint- Student versus Artist grade paints, brands, etc. and my current, idiosyncratic list of pigments (with some alternates listed as well).  Based on an understanding of sections one and two, folks should be better able to assess some of the reasons why I use the paints I do in section three.


Physical Characteristics of Pigments-


How Watercolor Pigments Work Physically-


Pigments are made up of dry colored powder that is carried in a binder.  A “binder” is a substance that holds the dry powder of the pigment together.  Different mediums use different binders, and each binder dictates the handling, drying, and “suspending” attributes of that specific medium.  The binder used for a pigment is one of the most important elements of what makes a specific medium itself.  Gum Arabic is the most common binder for watercolors, and unlike the viscous binders used for Arcylics or Oils (which permanently suspend the pigment particles inside of themselves) binders used in watercolors disperse when applied with water. 

Once applied, watercolor pigment is then held in suspension, using the water as a vehicle for movement.  As the water evaporates the particles of pigment remain, which sink into the fibers of the paper.  This process affects all kinds of crazy stuff- how we apply paint, how we make washes, how we work we-into-wet, what kind of paint we buy, etc etc.


Drying Shift-

the in-process wet version

the in-process wet version

the slightly paler and less chromatic dry version

the slightly paler and less chromatic dry version

Pigments generally look more vibrant when wet than they do in a dry completed painting.  This is called a drying shift.  I actually did a whole post on this in the Spring.  This occurs because pigment particles refract light differently when seen through the lens of the water than they do after having sunk into the fibers of the drying paper.  Drying shifts can be expressed through a loss of value, a loss of chroma (aka vibrancy), or a shift in hue (aka color).  As has been said before, “If it’s right when you’re painting it, then it’s not right.”  Given the physical nature of how watercolor works, you need to expect and anticipate drying shifts of some sort or another.


Lightfast and Fugitive Paints-

what we now see on the left, versus the artist's original vision on the right

what we now see on the left, versus the artist's original vision on the right

Some pigments are “fugitive,” and over time (sometimes in as little as a year or two!) they can become paler and/or duller if left in the sun- even reflected, indoor sunlight.  Yellows can become brown, reds become pink, etc.  I did a post about this last year, featuring many Van Goghs, but you don’t have to be famous for this to affect you too!  A number of well-known historically-used pigments, such as Alizarin Crimson and Aureolin Yellow, are notorious for this, and it is this fact which has affected the public perception of watercolors as a transient medium.  With the currently available range of pigments, it’s entirely possible (and in fact quite easy) to paint images that will last for hundreds of years, using only what are called “lightfast” pigments. 

Outside of some notable exceptions, most yellows and oranges are lightfast.  Earth colors are almost always lightfast.  Almost all blues and greens are as well.  However, many fugitive pigments are in the red, magenta and purple color families, and in this color range you still have to be very selective in your choices.  In the third section, I’ll provide a list of lightfast pigments to choose from, and note various common fugitive pigments to avoid.


Pigment Handling Characteristics

Like us, different pigments have different personalities.  You can have two different pigments that happen to share the same hue, and yet… they can give you quite different results on the paper.  It’s the pigment that matters, not the hue!  You can even have two tubes of paint that are the same pigment but different brands, and even they can act somewhat differently.  How the paint is made (is it extra finely milled? What kind of dispersant does it use?) can affect its handling characteristics. 

There are, in my mind, 5 basic characteristics we can use to describe pigments- are they Staining, Transparent, Opaque, Granulating, or Active Wet-Into-Wet?  Or some combination of them?  This section is, by far, the hardest to nail down, but really the one that affects us the most while painting.  The goal is not just to label the paints as this or that, Opaque or Transparent, etc, but rather to build an awareness of the ways in which our paints act, so that we can intentionally play to their strengths or ease into their weaknesses.  Sometimes, you have to know what to look for, before you can begin to see it, right?

Each handling characteristic has its time and place when it can be of use, and different types of pigments play to different approaches to painting.  One type is not “bad” and another “good”.  Rather, much depends on how you paint, and the types of handling characteristics an artist wants may change over the course of their painting career as their tastes change and develop.

Codifying things can helpful, but please pardon the generalities I make in the descriptions below-

Pigments that are very finely ground (which can settle deeply into the fibers of the paper) are generally Staining and Transparent.  Often times the two go hand in hand.  Many modern pigments fall into this category. 

Other pigments are considered Opaque.  They tend to have “covering power”.  They can leave a glaucous cast when washed over other layers with too thick an application, and tend to achieve a dense covering consistency with greater ease than Transparent paints.

Granulating pigments are made up of a combination of particle sizes, which separate out as they settle down into the paper.

Active pigments travel rapidly when charged into a wet wash.  Many modern, finely milled pigments are also very Active wet-into-wet.  Inert pigments tend to stay put when you put them in a wash.  Many are also mildly Opaque.

It’s also worth saying that many of these characteristics have a lot to do with how you dilute and apply the pigment.  For sure, if you mix a Transparent pigment up into a thick, milky consistency, they’ll eventually get opaque.  Similarly, you can take an Opaque pigment, dilute it with water in a big wet wash, and end up with a perfectly fine transparent application.  Again, apply an Active pigment with a small, thirsty, nylon brush and it won’t spread much at all.  On and on it goes.  The goal is not to be “trapped” by the handling characteristics of our pigments, but rather to understand them enough that we can anticipate the personality of each pigment before we apply it.


Characteristics of Common Families of Pigments-

This is a simple list to help aide one in the understanding of pigment categories, by name.  I wish I had had this when I began, and it took some time (on my own) to learn the basic, common attributes of different “families” of pigments.

Cadmiums are lightfast yellows, oranges, and reds that are semi-opaque when applied thickly, but are transparent when diluted.  It is an old pigment group with larger particles that is “heavy” and doesn’t move very much when applied wet-into-wet.  They are mildly toxic if ingested in large quantities.  Whether this is a real-world issue in practice is up for debate.

Perylenes are a modern pigment group, in the green to red range of colors. They are, as far as I know, very lightfast.  They are a muted pigment group, featuring deep, dark hues that are commonly used to mute other mixes.

Quinacridones are warm in hue, and are mostly reds, magentas, and purples.  They are a finely ground modern set of pigments, and often aggressively disperse when applied wet-into-wet.  They are lightfast.

Cobalts are lightfast greens, blues, and purples.  It’s an old pigment group that is granulating and “heavy”.  They are mildly inert wet-into-wet and are semi-opaque or “cloudy” when applied thickly.

Pthalos are very lightfast greens and blues.  It’s a modern group, is finely ground, and is very active wet-into-wet.  Pthalos are highly staining.