Pigment categories – part III

I’m going to finally get around to tackling that last category of pigments, the synthetic organics. There’s probably a reason for my tardiness: this is my least favorite group, and one that interests me very little these days. Recall that the three we’ve done before were: natural inorganic (these were the earths and natural minerals); natural organic (lake pigments, other pigments that come directly from plants and animals); and synthetic inorganic (the great chemistry accomplishments of the nineteenth and twentieth centuries, ultramarine blue, cadmium red, etc.). The story of the last category begins in the nineteenth century, but is mostly a twentieth century phenomenon.

Synthetic organic pigments

To the right are a few quick watercolor swatches using synthetic organic colors. Along the top row, left to right, are: Winsor & Newton manganese blue hue (it’s phthalo blue PB15); Sennelier lemon yellow (hansa yellow PY3); and Da Vinci alizarin crimson (it isn’t: it’s quinacridone violet PV19. Aren’t these marketing names great?). On the bottom row are a couple of mixtures from the three, a bright green from the phthalo and hansa, and a warm red from the hansa and quinacridone. I didn’t include a violet, since this particular red and blue don’t make a very saturated one; but to get a nice bright purple one need look no further than another synthetic organic, dioxazine violet. (The photograph was taken when the paints were still partly wet, and it captured the colors only tolerably well; the hansa yellow in particular is a bit warmer and more transparent than it looks here. Photography is definitely a skill I need to catch up on.)

There are so few real natural organic pigments in use any longer – mostly just the various carbon blacks – that the word “synthetic” is generally dropped from the term “synthetic organic,” having no other category to make it necessary; and these colors are simply called “organic,” since they by and large are the only organic colors out there. The name is a bit misleading at first. Most of us tend to feel a bit fuzzy when we hear the word “organic” – after all, usually it means healthy; it means natural; it probably means eco-friendly, cage-free, free-range, no hormones or pesticides, etc. However, in this case “organic” simply means that the substance in question contains a carbon molecule, and the feedstock from whence it was created probably existed, once upon a time, in the form of actual organisms. I’m talking, of course, about hydrocarbons: petroleum, natural gas, coal, etc. These substances are industrially heated, pressured and combined in various ways, sometimes with industrial acids or other chemicals (my knowledge is very weak on details here), to create the synthetic organic substances. Hmm… my fuzzy feeling has suddenly gone away.

From the Encyclopedia Brittanica: “Synthetic organic pigments are derived from coal tars and other petrochemicals.” By “coal tar” they mean the residue byproduct from burning hydrocarbons such as coal or natural gas. Some coal-tar colors began in the nineteenth century as dyes: mauve, alizarin crimson, the aniline colors – and some of these were laked to create the first synthetic organic pigments. (Some are insoluble to begin with, and don’t require laking.) The twentieth century embraced and expanded upon this line, notably with the azos, the phthalocyanines, the quinacridones, the perylenes, the anthraquinones, the pyrroles.

These are consumer colors – bright and saturated, capable of being produced on a tremendous scale, and cheap. They are truly modern colors, not only in the history of their production, but also in their flash and chromatic glory. Without these colors, the commercial world around us would be much less colorful than it is.

The benefits of these colors for artists are often cited. There is the very full range of color they make available to the artist, the ability to mix almost any color that could ever be needed by the average painter. They have provided excellent, durable replacements for older, less lightfast natural organic colors that have been weak spots in artists’ color wheels for centuries. They are inexpensive compared to some of the synthetic inorganic pigments, such as the cadmiums and cobalts. Finally, they are a less toxic alternative to those cadmiums and cobalts, and are increasingly turned to as the more toxic metals are falling under legislative ire.

So: what’s not to like? Follow me on later posts, faithful reader…

Tags: natural inorganic, natural organic, Pigments, synthetic inorganic, synthetic organic, watercolor