The arts and crafts world can sometimes be rather confusing because terms get tossed around with the assumption that the reader knows the meaning, but the terms are seldom defined. The terms “pigment” and “dye” are two such terms. What is the difference between pigments and dyes? What, actually, are they? And why does it matter which one you use?
Pigment Suspensions vs Dye Solutions
In a nutshell, the difference between pigments and dyes boils down to mud vs sugar-water. When you scoop a cup full of muddy water from a puddle, the water is brown. There is silt and dirt and mud particles suspended in the water. Given enough time, without being disturbed, the particles will settle out of the water and collect on the bottom of the cup. The larger particles will settle first and it might take many weeks or months for the finer particles to settle out. Chemically, this is called a suspension.
However, if you mix a spoonful of sugar into a cup of water, the sugar will completely dissolve into the water. If you let the cup of sugar-water sit, capped to avoid evaporation, on the shelf for a long time you will never get a layer of sugar particles settling on the bottom of the container. Chemically, this is called a solution. The sugar (solute) is dissolved in the water (solvent) to form a solution. (Remember it now? And you said you’d never have to use high school chemistry again! Ha!)
You intuitively know this about muddy water and sugar-water, and it helps to think of pigments and dyes the same way. Pigments, like mud, are finely ground particles of color which are suspended in a medium (such as water) to create a paint or coloring agent. Dyes are chemicals, like sugar, that are dissolved in a medium (such as water) to create a paint or coloring agent. Notice the difference in words there…suspended vs dissolved. Mud vs sugar. Makes sense, doesn’t it?
A pigment paint, when applied to a base such as paper, will lay on top of the paper. It will form a coating over the paper. Of course the fine particles of the pigment can get stuck in between the paper fibers and will stain the paper in much the same way that dirt will get ground into the knees of a 6 year old’s jeans. But the particles are physically, not chemically bound. It’s painted on. (And it’s the medium, such as the paint carrier, that makes it stick to the paper.)
A dye, on the other hand, will chemically bind to the paper. Some dyes might need another chemical, called a mordant, to make that happen. If you’ve ever dyed fabric you know that some types of dyes only chemically bind to some types of fibers. But in general a dye will bind to the material you’re using it on. It’s not painted on the surface. It becomes part of the material.
Origins of Pigments and Dyes
Pigments are created from all kinds of natural substances, and historically our first pigments were created from natural materials. Like mud. I’m sure you’ve noticed that mud comes in many colors and you might even know that mud from certain regions of the earth are known for creating certain colors. The name of the artist’s pigment umber comes from Umbria, a region in central Italy. Finely ground mud was mixed with oil to create raw umber paint. If the mud pigment was heated first, the resulting pigment was called burnt umber. Similar earthen pigments include ochre and sienna. Our resourceful ancestors found pigments in all sorts of ways. The black soot from an oil lamp was used to create lamp black. Chalk was used to make white. Ultramarine blue was made by grinding lapiz lazuli, a blue stone. The complex history of pigments is fascinating and well worth exploring if this interests you.
Dyes, on the other hand, are colored chemicals that are either a liquid themselves or are easily dissolved in a liquid. Our ancestors made dyes from natural materials such as bark, berries, roots and even (gasp) insects. Not all dyes are soluble in water. Another factor is that many dyes are not stable in light and will fade, sometimes quite rapidly, when exposed to light. Especially sunlight. (This is true for some pigments as well, which is why art museums keep the lights very low to protect the paintings.)
Nowadays, pigments are mostly synthetically produced and we have a wide range to choose from. Modern chemistry has provided us with a huge array of clear colored, bright, stable, and generally non-toxic pigments to use for our artwork. Sometimes the better pigments are quite expensive, though, and so cheaper materials will often contain lower quality pigments or even use dye coated pigments.
Use of Pigments vs Dyes
Artist’s paints are made from pigments. Watercolor paints are created from very finely ground pigments suspended in a carrier which is packaged either in a tube or pressed into a cake or pan. Artist’s oil paints are made from pigments which are suspended in linseed oil. And artist’s acrylic paints are pigments which are suspended in an acrylic medium.
We are, of course, familiar with using dyes to dye fabrics. But we actually use dyes in surprising ways in the arts and crafts industry. Permanent markers, such as Sharpie brand markers, are made with dyes. Alcohol inks and markers are made with dyes. And some stamp pads are made with dyes.
Why does this matter? Well, knowing if you’re dealing with a dye or a pigment does help you understand how to use the material. An example would be opacity. In general, because pigments are particles, pigment based colors are more opaque. Because dyes are not made from particles that coat a material, light transmission is not affected and using dye-based colors will make a more translucent effect. Therefore, if I need to make a clear piece of glass completely opaque, it helps to know that black acrylic paint will block the light but a black Sharpie will not.
Also, because light goes through a dye rather than bouncing off it like with a pigment, mixing colors of dyes usually gives a more light-friendly result. That’s a fancy way of saying that mixed pigments often look muddy, but mixed dyes create clear colors.
Basic colored stamp pads tend to come in two broad types, pigment based and dye based. Now that you know a bit more about pigments vs dyes, the difference between these two becomes more clear. Pigment based stamp pads are more opaque, the color doesn’t fade, it doesn’t bleed through the paper, and you can paint over them with watercolors or other inks without bleeding. Dye based stamp pads don’t have these qualities, but do dry much faster because they absorb into the paper. The qualities of a dye based stamp design might be favorable if you’re doing a mixed media work and need the color to bleed. The key to use is knowing what qualities you need for your final result.
Markers are also pigment vs dye based. Permanent markers are almost all dye based. Sharpie, Copic, Spectrum Noir, dry erase markers, children’s markers, Microperm markers, and even ball point pens are all dye based. But there are some noted exceptions. Paint markers are, of course, pigment based. The PITT series of drawing pens is pigment based as are Pigma Micro drawing pens. And relatively new on the market are a whole line of acrylic markers such as Montana markers. These gems look and act like any marker but are more opaque, do not bleed, and don’t fade in sunlight. Those qualities make them a favorite of graffiti artists.
India Ink is a pigment based ink. Both Ranger and Pinata alcohol inks are dye based. The rich, but fugitive (fades in light) colors of Dr. Ph. Martin’s Radiant Concentrated Watercolors are a dye. But there are colored inks which are created from pigments. Both Liquitex Acrylic Ink and Daler Rowney FW Acrylic Ink are pigment based.
As an interesting aside, you can buy empty Copic markers. And you can fill them with Liquitex Acrylic Ink. Yes, I have a lovely acrylic marker with a Copic brush tip. It’s very nice for drawing on polymer clay. If you’re looking to draw on polymer clay, I did a comparison of several brands and types of markers that might interest you.
A Word about Vehicle
Vehicle is the carrier, or medium that a dye or pigment is dissolved or suspended in. The waterproof quality of a paint or product has nothing to do with the colorant and everything to do with the vehicle. Raw Umber is a pigment that’s basically dirt. You can wash it off with water. But when mixed with linseed oil, as in artist’s oil paint, it becomes waterproof. Dried raw umber acrylic paint, although water based and water washable, is waterproof once dried. But raw umber watercolor paint will wash right off your brushes, even after drying. It has to do with the medium.
Pigments and dyes can both be carried in a vehicle. If the dye is dissolved in a medium, such as water or alcohol, you can “paint” with a dye. After all, that’s what a Copic marker is!
Some dyes will not dissolve in some liquids. Or need to be dissolved in one liquid before being mixed with another. There’s a whole area of chemistry that has to do with solubility constants and math and I’ll spare you that part. But keep in mind this is why you sometimes get unexpected results when working with polymer clay. The chemistry can be a bit…interesting at times.
Why this Matters in Polymer Clay
Polymer clay is colored with pigment. That is why it is opaque. Translucent polymer clay doesn’t have (much) pigment, that’s why light can shine through it. If you mix a pigment based colorant into your translucent polymer clay, you will be decreasing the translucency (a bit like creating muddy water). For some colors, such as yellow, you won’t use very much color and it won’t create much light blockage. But when you tint translucent polymer clay with a dye, such as alcohol inks, you are able to color the clay quite vividly without affecting the translucent quality (except at high levels or with very dark colors). Also, because pigment colors can get muddy when the colors are mixed, polymer clay colored with dyes can give you more vibrant color mixes and gradients than if you try to create them with pigmented colors.
A drawback of this, though, is that dye mixed with polymer clay can bleed. So if you make a cane with dye-tinted colors of polymer clay, the colors can diffuse and get blurry over time. It’s just something to keep in mind. Baking the polymer clay does seem to fully stabilize the dye colors, though. I have not seen evidence of dye bleeding in baked clay.
So Is My Craft Product a Pigment or a Dye?
How can you tell if a specific product is made with a pigment or a dye? Well, it can be confusing. The best way to know what you’re dealing with is to read the label and the manufacturer’s literature. If it’s very important to you to know what’s in your art materials, I suggest that you stick with professional and artist’s quality materials. Artist’s paints, for instance, will typically tell you exactly what the pigment is and how transparent it is, its lightfastness, and other things like hue, value, and saturation of the pigment. Craft paints will not tell you this and will often change formulation often without any standardization of color. Some brands of polymer clay are notorious for doing this, by the way.
Bottom line, if you’re getting unpredictable results with your materials, give some thought to the chemistry of it. And whether or not you’re working with a pigment vs a dye might very well be affecting your results.