Alyssa Dumire, Director of Education
We know what color is, but where does it come from? What factors, beyond basic color theory, influence an artist’s color choices? How has access to certain colors changed over time? These are questions we’ll be exploring in a new series of Art Term Tuesdays over the coming months, one hue at a time. But first, it’s important to gain a basic understanding of how colors work in different media, and some general knowledge of where they come from. Today, we’re tackling pigments and dyes, two different vehicles for applying color (yes, there is a difference!). These are not the only systems by which color is achieved, but they are among the simplest and most common.
Generally, paint is mixed using pigment colorants. Pigments have a relatively large particle size, which means they must be suspended in a binder. For oil paints, the binder is linseed oil. Acrylic employs a wide variety of mediums to adjust its texture, tempera traditionally uses egg yolk, and watercolor gum arabic. If you recall comparing different kinds of mixtures in chemistry class, that knowledge will come in handy here: paint that is composed of just a binder (or dispersing agent) and the pigment is a colloid but, if it also has a solvent added, it’s a suspension. Suspensions will settle over time and need to be mixed–think of those classroom-size jugs of tempera that always benefit from a good shake or a can of house paint (the hardware store gives you free stir sticks for a reason).
On the other hand, dye particles are much smaller than pigment particles, allowing them to dissolve in water and chemically bind to the material, or substrate, to which they are applied (like your clothes). While dyes become one with their substrate, binding on a molecular level, pigments sit on top; and, because dyes form a solution, they are transparent, while pigments (again, generally) are opaque. It might sound like dyes are superior to pigments, but for one trait: lightfastness, or the tendency to fade under ultraviolet rays (sunlight). UV light can break the bond between dye and substrate, causing dyed materials to fade, with different colors fading at different rates. Pigments, with few exceptions called fugitive pigments, tend to be much more lightfast. From a conservation standpoint, this means we worry far less about paintings’ long-term exposure to light than we do works on paper. Quilts and other fiber-based artworks are also prone to fading, and specific hues are more susceptible than others.
What about ink? That depends! India ink, used for drawing and painting, uses lampblack, a type of fine soot, as a pigment but, because it’s so fine, it forms a colloidal suspension in water and needs no binder. It is also permanent. Fountain pen ink is dye-based so the solution doesn’t clog the pen. Printmaking inks are pigment-based, which is evident in the way they sit on top of their substrate as in a screenprinted t-shirt.
The study of color is full of science (STEAM!). For both pigment and dye, physics determines what color we see based on the wavelength of the light reflected. Developing various dyes and pigments also requires chemistry, and naturally as humans have made new discoveries and developments in the field, colorants changed and evolved alongside. Paintings, in fact, can often be dated based on the specific hues used (a bane for ill-informed art forgers!). The earliest colors used in artworks came from the earth, and while these mineral-based colorants are still available, many more are now synthetic (made in a lab) and not just for artistic applications. Over the coming months, we’ll explore both ends of the color history timeline, hue by hue, to see how factors like geography, economics, and symbolism impact the art we enjoy.