The Anatomy of Paint: Pigment and Binder

raw umber and natural ultramarine pigments
Raw umber (left) and synthetic ultramarine (right)
pigments in powder form

"For the twentieth-century painter, who normally regards paint as a pasty substance of a certain color that can be squeezed from a tube, it is hard to imagine that to artists not only of the fifteenth and sixteenth centuries, but also of the seventeenth, the eighteenth and the first half of the nineteenth century, each pigment presented its own inherent possibilities and limitations. Some pigments could not be worked-up with oil; some pigments could only be safely mixed with one or two other pigments; some pigments could only be used transparently and yet others only opaquely. Other properties, too, such as color permanence, workability, drying qualities, and so on, could differ so strongly from one pigment to another that it was normal to use a given pigment in pure form or mixed with a limited number of other pigments when modifying tone and color."1 In fact, many mixtures of paint in Vermeer's painting usually contain no more than two or three different pigments.

Artist's paint consists primarily of two components: pigment and binder. In order to produce paint, pigment and binder are ground into a stiff paste which must have three requirements: it must be brushable, it must adhere permanently to the support's surface and it must not alter significantly in time. In the Netherlands canvas and panel were preferred as supports but copper was also used for fine work such as flower painting and small-scale genre scenes. Through chemical analysis, it would appear that Vermeer employed the same materials to produce his paints as those employed by his contemporaries.

Pigment

Pigment is the actual coloring substance of paint. Pigment has body in contradistinction to purely visual color. It is usually of mineral or organic origin although some, like the all important lead white, were and still are artificially produced. Pigments vary considerably in weight, transparency and physical structure. For example, alizarin comes in the form of an extremely fluffy, light-weight powder, one pound of which will almost fill a half-gallon can. A pound of vermilion will go into a four-ounce jar. On the other hand, earth pigments and the touchstone lead white are so bulky that one can easily perceive their granular structure with the naked eye.

lapis lazuli
A piece of unprocessed lapis lazuli from which the pigment natural ultramarine is made.

After being first separated from gross impurities, the raw pigment must be thoroughly cleansed and carefully ground to the proper coarseness. Some pigments must be finely ground while other lose their color if they are over ground. The great part of artist’s paints were once made with earth pigments, or natural inorganic pigments - simply put, colored clumps of earth each with a different color. An example for a natural mineral pigment is the popular yellow ochre, which is made from extracted earth. An example of a modern manufactured mineral pigment is cobalt blue, which is made from oxidized cobalt compounds.

Earth pigments were the first pigments used by mankind and include such colors as the siennas, the umbers, green earth and a wide range of ochres. These pigments are usually heavy in weight and lightfast. They have good wetting properties and produce opaque, solid colors. Another great advantage of earth pigments is that they are entirely stable in all painting media and do not interact chemically with the sensitive pigments making them suitable for mixing with almost every pigment available to the artist. Ochres are the most opaque of the earth pigments.

Artificial inorganic pigments, on the other hand, are colors that are manufactured rather than found. Many of these pigments were made and discovered by the alchemists of antiquity. Verdigris, Naples yellow and the all-important lead white fall into this category.

Natural organic pigments have sources that are either vegetable or animal, rather than earth or mineral. Organic pigments can be natural, derived from plants, or manufactured, made from complex hydrocarbons. Examples of ancient organic pigments are indigo and red madder, Indian Yellow (urine from Indian cows fed only on mango leaves), sap green, and bone black (calcinated bones). Modern manufactured organic pigments, having been originally derived from coal-tar based dyes, now include almost any shade of color imaginable. Almost all the pigments used in modern artists' paints are man-made chemicals, developed in many cases as substitutes for rare, expensive, or unstable natural colorants of plant, animal, or mineral origin.

Binder

The binder, commonly called the vehicle, is the film-forming component of paint. A pigment should not dissolve in the binding medium nor be affected by it. Many colors, such as lead white or umber, accelerate the drying of the oil; others, such as the lakes and vermilion, retard this process. In general the dense, heavy pigments dry well and quickly, since they require little oil.

Although egg tempera had been exclusively employed as the painting medium in medieval times (and is still employed by some specialists), it presents serious limitations for painters used to the flexibility of oil painting. By the time Vermeer began painting, tempera had almost been completely abandoned for its many shortcomings.

Tempera paint could not be stored, so each color was mixed when it was needed and once dry on the palette, it cannot be used again. Because it dries very quickly, artists had to paint small areas of the composition one at a time. The fast drying time made smooth blending difficult if not impossible and painters had to use time consuming and problematic techniques to paint over a dried layer of tempera without disturbing the underlying one. In general, tempera painting has to be executed quickly and lightly and is exceedingly tedious when compared with oil painting. Although paintings executed with tempera have a lively, colorful appearance, when dry, the dark passages appear signifi­cantly lighter in tone giving a total impression of diffused daylight. It is therefore impossible to suggest the strong contrast that was necessary to convincingly describe form and above all light, perhaps the foremost prerogatives of sixteenth- and seventeenth-century painting.

The advantages of oil painting in respects to tempera are so many that they are almost impossible to inventory. Oil paints can be blended to create infinitely fine gradations even with ordinary brushes. It is possible to overpaint as many times as is necessary covering entirely the lower paint layers. Both the natural opacity of some pigments and transparency of others can be exploited to suggest a truly vast array of optical effects. Furthermore, great quantities of oil paint can be applied to obtain textured surfaces while at the same time it permits the accomplished artist to create the finest details imaginable with ease. Unlike tempera, dark tones remain dark and a painting properly executed in oils has an agreeable glossy or semi-glossy appearance. Oil paint allowed the artist to develop rich colors, depth and shading from light to dark creating outstanding atmospheric effects. Painters could rework their initial thoughts and dramatically change the composition - there seemed to be no limit to the range of expressive possibilities that the oil paint medium could afford. Therefore, it is not surprising that today oil paint is universally considered the most flexible technique for artistic expression and has largely supplanted techniques of the past.

In order to produce good oil paint, pigment and binder are ground into a stiff paste which must have three requirements: it must be brushable, it must adhere permanently to the support's surface and it must not alter significantly in time. Some pigments require long periods of grinding to make them usable and some must be ground only shortly otherwise they quickly lose their natural brilliance. Some pigments, like ultramarine, produce a fastidious stringy paint although additives may be introduced such as wax, alum, chalk or dryers to correct deficiencies or augment inherent properties. Linseed, nut and poppy oil were by far the most popular binders.

Through countless hours spent grinding pigments with a muller against a slab, Medieval and Renaissance painters learned invaluable information about their materials which aided them in creating masterpieces of their time. Although the knowledge gained through direct experience has been largely lost it is still possible to make suitable paints in the studio without excessive difficulty provided one comprehends the fundamental requirements of fine arts paint.

Vermeer's Binding Medium

Data thus far gathered indicates that Vermeer painted entirely with oil paints. Although there is evidence of a sporadic presence of a water-based protein medium in connection with two specific pigments (azurite and smalt), these paints occur only in the lower layers of the paint surface and seemed to have been used chiefly for economic rather than aesthetic purposes. In any case, due to the limited sampling opportunities inherent in working with such precious objects, there exists scant information which might tell us which drying oil(s) Vermeer used to bind his pigments but it is very likely he employed only materials widely known among his contemporaries. He may have also followed the practice of using different binding material for different pigments as was recommended at the time. Lighter cool tints were ground with walnut or poppy oil, which tend to yellow less that other oils, and warmer and darker tints were ground with linseed oil.

"Recent analysis of paint samples by researchers in the Scientific department at the National Gallery using a technique known as gas chromatography-mass spectrometry (GC-MS) has shown that the binding medium of the ground layer in Young Woman standing at a Virginal is a heat-bodied linseed oil. A sample of dark-coloured paint obtained from the background to the right of the chair at the lower right-hand edge of the picture was also bound with a heat-bodied linseed oil. In fact, linseed oil is by far the most common binder found in seventeenth-century Holland and has been identified at the National Gallery in works by Jan Steen and others."2 In The Art of Painting, walnut oil was identified as the binder in a sample of white paint, while linseed oil was identified in a paint sample described as blue-green in colour.3 No white paint was analysed during the examination of a Girl with a Pearl Earring, but linseed oil was identified as the binder in both a sample from the ground layer and from the dark background.4

Transparency and Opacity

Today’s artists are sometimes surprised to see how variable in opacity pigments can be. Some pigments produce a glass-like effect which barely hides the underdrawing while other seemingly opaque ones do not fully cover it. Other pigments mask all that was underneath. These differences are experienced by painters of the past and present because each pigment, depending on its chemical properties and methods of production, has its own character which must be reckoned with.

An opaque paint is one that transmits no light and can readily be made to cover or hide what is under it. A semi-opaque paint transmits very little light, but is incapable of concealing dark colors and strong markings under it unless an unusually heavy coat is applied. A transparent material transmits light freely; when a transparent glaze of oil color, for example, is placed over another color, it produces a clean mixture of the two hues without much loss of clarity. A semitransparent paint transmits much light, but is not clear; a semitransparent glaze, when placed over another color, will produce a pale or cloudy effect because of the reflection of light from the surface. Semi-transparency and semi-opacity are also known as translucency. Pigments are classed as opaque, semi-opaque, and transparent.

In painting techniques, opaque and transparent pigments produce color effects in two different ways: Watercolor employs transparent color, relying on the brilliant white paper to create white and pale colors; casein, gouache, and pastel are completely opaque, using white pigment to obtain whites and pale colors; tempera is semi-opaque, combining the effects of both systems; and oil painting is capable of utilizing opaque, translucent, and transparent effects, sometimes all in the same painting.

The hiding strength of paint is largely influenced by the relative refractive indices of the pigment and the medium, as well as the particle size and distribution of the pigment, the proportion of pigment in the vehicle and the thickness of the applied film. Transparency depends largely on the physical characteristics of the pigment itself rather than how it is bound to the vehicle. Good red madder will always be transparent, no matter how it is bound or applied except, of course, if it is mixed with white which provides an excel­lent pink hue. And on the other hand, vermilion will always be one of the most opaque pigments and it is precisely in its opacity that the Great Masters found it most useful. These paints must be used according to their intrinsic qualities.

Many inexperienced painters would prefer to have paints of all the same opacity. This is a mistake. The breadth and depth of the Masters’ works is as much consequence of the inequality of transparency of their pigments as the way they are applied to the canvas.

  1. Ernst van der Wetering, Rembrandt: The Painter at Work, Berkeley, Los Angeles and London, 2002.
  2. Helen Howard, David Peggie and Rachel Billinge, Vermeer's Palette, "Binding medium", National Gallery website, <http://www.nationalgallery.org.uk/paintings/research/meaning-of-making/vermeer-and-technique/binding-medium>
  3. J. Boon and E. Oberthaler, 'Mechanical Weaknesss and Chemical Reactivity Observed in the Paint Structure and Surface of "The Art of Painting"' in "Vermeer, "The Art of Painting": Scrutiny of a Picture', exh. cat., Kunsthistorisches Museum, Vienna 2010, pp. 328–35.
  4. K. M. Groen, I. D. Van Der Werf, K. J. Van Den Berg and J. J. Boon, 'Scientific Examination of Vermeer's "Girl with a Pearl Earring"', in I. Gaskell and M. Jonker, eds., Vermeer Studies, New Haven and London, 1998, pp. 169–183.