This is a subtle point that doesn’t often come up in the classes I’ve taken, but nevertheless understanding it can save you a lot of grief at your art table.
Which is that while watercolors might all look similar in their tubes or pans, they are not. Some of them are pigments, and some of them are dyes.
So what’s the difference? A big one.
A pigment is basically dirt.
It is tiny particles of pigment, finely milled and suspended in a binder. When you get it wet, it becomes very fancy mud.
A dye is water soluble.
Unlike a pigment, which is particles of color suspended in a binder, a dye actually dissolves in the water. It’s been fixed with a mordant to make it lightfast on the paper, but it still dissolves real good. If a pigment is mud, a dye color is a glass of red wine.
They behave relatively similarly to paint with, but one is permanent and one is not. Dye colors are permanent. While pigments sit on top of the paper, dyes go in and effect the actual fiber of the paper. It’s the difference between getting mud on your shirt or spilling wine on it.
This makes a difference when you’re painting, because you cannot rewet and manipulate a dye color later. Once they touch the paper, the paper is that color now. They are the most unforgiving of the watercolor family.
But they’re not all bad. Dye colors are also generally appreciated for their vividness and transparency. Because a dye color fully dissolves in water, they are fully transparent. They aren’t something to avoid, but it’s helpful to know the difference.
Here’s a list of dye colors that I’m aware of and use (I’m sure there are many more):
Bright Red, Prussian Blue, Indigo, Cadmium Scarlet, Scarlet Lake, Vermilion Hue, Cadmium Red, Winsor Red, Rose Doré, Permanent Alizarin Crimson, Permanent Rose, Winsor Blues, Winsor Greens, Winsor Emerald, Hooker’s Green, Permanent Sap Green, Alizarin Crimson, Olive Green, Gold Ochre, Venetian Red
So if you’re painting along and you come across a color that won’t budge once it’s touched the paper, you’ve met a dye color.
Don’t panic. They’re here to help. A dye color is your best friend in creating that beautiful watercolor layered effect, because they are truly transparent. They are the perfect solution to wanting a tiny dab of color on top of 5 others, without making a mess. They’re the most watercolory of the watercolors. And, they’re permanent as heck.