A class member recently asked a great question about the difference in watercolor pigments and I thought I would share the answer here.

“I was wondering about pigment. There are many “Quinacridone” pigments and they differ from other pigments such as a “cadmium” I understand that some are “organic” and others are not. I was hoping that you may be able to go through this. How do they different? “

First of all, let me say that pigment talk is not my favorite subject because I’d rather paint than think about how the paint is made! Haha. Don’t spend too much time thinking about the chemical makeup of paints — just paint and you’ll get to know your paints. Okay, here goes my technical talk…

Pigments can be either natural or synthetic.

  • Natural: means just that, ground up stuff that can be found on earth
  • Synthetic: has been derived from a chemical process

Also, they can be inorganic or organic.

  • Inorganic: a mineral compound (derived either naturally or chemically) that does not contain carbon
  • Organic: contains carbon in combo with hydrogen, nitrogen and other fancy things.

I think what confuses most painters is the word “organic” because we associate that term with organic carrots at the farmers market. In the chemistry world, “organic” means that it contains carbon. So I just substitute the word carbon when I’m trying to remember the difference in pigments —- which happens to be ONLY when I’m being asked about it! 🙂

So based on those categories we have:

  • Natural inorganic pigments — mined from the earth and pulverized (no carbon)
  • Synthetic inorganic pigments — created in a lab using metal or mineral compounds (no carbon)
  • Natural organic pigments — ground up plant or animal matter (carbon). Very rare these days because they not sustainable or lightfast. Egyptian mummy paint was actually a thing back in the day! Can you imagine… “Oh darn, I’m out of brown paint, gotta find me a mummy.”
  • Synthetic organic pigments – carbon based pigments made in a lab

Most of the pigments I use are either natural or synthetic inorganic pigments; yellow ochre, burnt sienna, cadmiums, cobalts, ultramarine. And I use some synthetic organic pigments. Synthetic organic pigments include quinacridones, phthalos, dioxazine, naphthol, anthraquinone. This group usually tends to be more vivid, transparent and staining. Those carbon atoms form strong, stable chemical bonds. I think of these guys as dye in a tube to help me remember the difference.

If you’re like me and saying, “What the heck?” right about now, don’t worry. To keep things less confusing for us painters, most paint manufacturers categorize their paints as

  • staining or non-staining
  • transparent or opaque
  • lightfast or fugitive

This is an efficient manner for painters to understand the difference in paints because that’s what matters most when applying the pigment. These descriptions can be found on the websites of most paint manufacturers and even on some paint tube labels.

Again, I advise people to paint more and think less. Yes, you do need have a selection of pigments that works well for your style and subject matter. And you’ll want to have paints that make it easy for you to mix the colors you need. Also getting a new tube of paint can be really fun and exciting! However, if you find yourself obsessing over the difference between (PB 15:0) and (PB 15:3) then you may need to get off the internet and pick up a paint brush. 😉

*Disclaimer, I got an A is chemistry only because  I picked the smartest boy in class as my lab partner. So there could be tragic errors in my post.

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