handprint : earth pigments tour
 

earth pigments tour

 
Iron oxide or "earth" paint marketing namesyellow ochre, raw sienna, burnt sienna, raw umber, burnt umber, venetian red, mars violet — do not exactly stand for specific pigments or colors in the way that ultramarine blue or viridian do. They stand for a traditional color concept that each paint manufacturer interprets in their own way, using varieties of iron oxide with loosely defined chemical or color characteristics.

The sheer diversity of earth paints on the market today makes it hard to understand the basic color concept each type of pigment represents. This page explains the key differences and defining features.

First, a map will help. The image below shows the individual earth pigments from 7 major watercolor paint manufacturers plotted on the CIELAB a*b* plane. (The section on creating a color wheel explains how to interpret a hue plane diagram.) The image opens as a separate window to facilitate visual comparison as you read the discussion. In this kind of map:

• Red colors are placed toward the right, and yellow colors toward the top.

• Gray or black colors are at the bottom left corner, and as a paint's color becomes more intense or saturated, it is located farther away from this corner and closer to the circle.

• The hue angle, which is listed for each paint in the guide to watercolor pigments, is indicated by blue numbers along the circumference.

Paints within the same earth color category are shown by the same colored diamond, and linked or enclosed by gray lines. This shows you the pigment variation within each color category, and the relative location of each category in the color space.

 

 


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Five synthetic organic pigments have been inserted to mark the location of yellow, deep yellow, orange, red orange and red on the a*b* plane, and the approximate maximum chroma of watercolors for each hue. All "earth" colors have hues between deep yellow and scarlet with moderate to low chroma; the umbers (including mars violet) have lower chroma than siennas and ochres.

Why so many earth pigments? There's always competitor pressures, and the irrational consumer appeal of venerable or exotic paint names, to explain why some paint companies offer so many earth pigments. But iron oxide, with trace metals and water included, is a relatively inexpensive and very versatile pigment, and it creates colors in a color vision area that is especially sensitive to differences in color lightness and chroma. This is why they are among the oldest pigments used in art.

Let's get some clarity about the ten most commonly manufactured earth color categories:

• YELLOW OCHRE. This term defines a fairly well focused color concept: a mid valued, moderately dull, semiopaque deep yellow at a hue angle between 65 to 70. The name is derived from yellow brown limonite (historically sometimes called "French ochre") found in many locations around the world, and easily manufactured iron oxide of the same color. It has been used almost continuously in painting and fresco since antiquity, and this continuous usage has kept the color concept well defined. Variations in the paint lightness and chroma arise from differences in the presence of manganese, particle size, and pigment density in the paint.

The narrow wedge of color markers indicates that the hue is generally a cooler yellow than raw sienna. The pigment is also usually darker valued and is much more opaque. During rinsing, some brands will cling to the brush with an almost greasy tenacity. Most brands stain only slightly and lift fairly easily.

• RAW SIENNA. The variation in hue among the currently offered raw siennas is larger than for any other "earth" category, which I would summarize as a mid valued, moderately dull deep yellow at a hue angle between 60 to 70. The color of raw sienna resembles dried meadow grass, pale fresh cut woods such as maple or pine, and weathered plaster. I believe the Winsor & Newton formulation is closest to the historical color, which is slightly lighter valued, less saturated, cooler (more yellow), and much more transparent than yellow ochre; the differences between raw sienna and yellow ochre become less pronounced in tints, though raw sienna usually shifts farther toward a bright yellow.

Most raw siennas are nonstaining and lift easily. However, the key attribute its transparency. Only Daniel Smith (monte amiata natural sienna) Maimeri, Old Holland and Winsor & Newton seem to have pursued this quality. In contrast, other brands are darker valued than yellow ochre, warmer, and comparably semiopaque. Some companies (Utrecht, M. Graham) seem to select their sienna and ochre pigments to contrast the color appearance as much as possible, while others (Winsor & Newton, Daniel Smith) contrast the paints in transparency more than hue.

Typically, mars yellow falls within area covered by the least saturated raw siennas, and is darker valued. It's made of the same pigment as yellow ochre (PY43), but is a warmer and duller color.

In my 1998 lightfastness tests I discovered some lightfastness problems in yellow iron oxide paints (a few brands blackened slightly after prolonged exposure to sunlight), but I was unable to duplicate these in 2004 using a more rigorous test.

Finally, chrome titanate (PBr24) is worth considering as a lightfast alternative with beautiful color characteristics. It has a naturally light, whitened color that is very useful as a foundation tint; unfortunately it's not as transparent as a good raw sienna, and therefore can't be used as frequently or effectively in glazes over other paints, unless a hazy whiteness is desired.

• RAW UMBER. Paints in this color category vary widely in chroma, as shown by the radius of color markers extending from the center of the a*b* hue plane. But most are a dark valued, dull, semitransparent deep yellow at a hue angle around 65. The color resembles sun bleached lumber, The darkening is due to manganese compounded with the iron oxide. Again, the Winsor & Newton paint is probably closest to the historical (19th century) color, which was a transparent, greenish, mid valued deep yellow. Nearly all other brands are much darker, more opaque, and much less saturated.

I believe the paint name "raw umber" is a relatively recent innovation, as comparable pigments were sold in the 19th century and earlier under a variety of regional names. These names persisted to mark the large color variety among these pigments. The huge effect that small chroma or lightness differences can have on a deep yellow paint are nicely displayed in raw umbers. The most saturated or lightest valued paints (Winsor & Newton, Maimeri) have a fawn or grayish green appearance, while the least saturated or darkest (Rowney Artists, M. Graham) have a dark, grayish color resembling a diluted black.

Again, transparency is a key attribute of a good raw umber, and across brands raw umber is the most transparent of all earth pigments. Even so, some brands (Winsor & Newton, Maimeri) capture this attribute better than others (Daniel Smith, DaVinci). The darker brands are also more staining.

Within a single paint line, raw umber is most often positioned as darker, less saturated "pigment sibling" to raw sienna or yellow ochre, which are siblings to a deep yellow such as nickel dioxine yellow or hansa yellow deep. But some brands (Winsor & Newton, Maimeri) keep the color differences among those paints relatively small, while others (Daniel Smith, Utrecht) make them quite large. Rembrandt strikes a happy medium.

• QUINACRIDONE GOLD (PO49). This pigment is no longer manufactured; paint companies who carry it are formulating (or have already introduced) replacement mixtures. As a synthetic organic pigment manufactured to fairly close chemical specifications, the various quinacridone gold paints had very similar hue and were separated only slightly in chroma. The color is midway between a deep yellow and orange, slightly warmer than the typical yellow ochre or raw sienna. Unlike most pigments, the paints actually gained chroma as it was diluted, and it was completely transparent.

Winsor & Newton gold ochre (PY42) is an interesting yellow iron oxide alternative, a slightly dull, light orange hue that is very effective as the yellow paint in landscape, mixed portrait and figure flesh tones. When diluted to a tint, the color is indistinguishable from a moderately diluted raw sienna.

• BURNT SIENNA. Burnt sienna is traditionally a yellow iron oxide darkened by "burning" or roasting in a kiln. This shifts the hue about 30 degrees from deep yellow to red orange (scarlet). Most paints are a dark valued, moderately saturated, semiopaque red orange at a hue angle around 40. The color resembles bread crust, dark redwood, and suntanned caucasian skin. Burnt sienna is perhaps the most popular and useful of all earth colors; few artists paint without it, and it is easy to rely on it too much. As the chart shows, the variation in hue and value among the different brands of burnt sienna is comparatively small, but the color is poised on the boundary between orange and brown, so even small differences in chroma have a pronounced effect on the color.

The largest difference among the various brands of burnt sienna is in transparency: the paints by Winsor & Newton and Robert Doak are made with a transparent red iron oxide of very small particle size and a near orange color, while other brands are made with a coarser, darker, more opaque pigment that is definitely brown. All the paints strongly shift toward deep yellow in tints.

Paint brands vary widely in transparency; it is wrong to say (as many watercolorists do) that burnt sienna is an "opaque color". Some brands (M. Graham, Daniel Smith burnt sienna) are indeed opaque, but a few (Winsor & Newton, Rowney Artists, MaimeriBlu transparent mars red, Daniel Smith terre ercolano) are made with a transparent synthetic iron oxide (PR101). Even these will become dull and opaque if laid on thickly or in many glazed layers.

A very interesting alternative to burnt sienna is the slightly lighter valued and more transparent quinacridone orange which is only available in a single paint: Daniel Smith quinacridone burnt orange, PO48). This is a darker, warmer shade of yellow quinacridone that is slightly more intense and transparent than the most saturated, most transparent iron oxide burnt sienna.

The infrequently offered light red is approximately the same hue and chroma as burnt sienna, but lighter valued and more opaque.

• BURNT UMBER. This is traditionally a yellow iron manganese oxide that is darkened by furnace roasting, which shifts the hue about 15 degrees from deep yellow to orange. Most paints are a very dark valued, semiopaque, dull orange (brown) at a hue angle around 50. The color resembles dark chocolate, and is yellower than burnt sienna. Again, burnt umber serves as a "pigment sibling" to the brighter, lighter and warmer burnt sienna.

As with raw umber, the primary color variation is in chroma and lightness, within a narrow range of hues: the paints fall along a fairly straight line toward benzimida orange (PO62). Reading from the most intense paints toward the center. M. Graham and Winsor & Newton have the most saturated color, while Daniel Smith and MaimeriBlu are the darkest and dullest.

Typically, mars brown most resembles the hue and chroma of a burnt umber paint, but is much lighter valued (about the same as a burnt sienna).

Natural van dyke brown, made from heavily carbonized peat, is even darker valued and closer to black. Because the original color is not lightfast, modern paints usually duplicate it by mixing burnt umber with carbon black.

• VENETIAN RED. This was originally a red ochre pigment imported from Cyprus via the Adriatic trade through Venice, and now manufactured with synthetic pigments. It is sometimes called English red or mars red. It represents a fairly specific hue concept (rust red, literally); most paints are a dark valued, moderately dull scarlet at a hue angle around 33. The color varies across manufacturers primarily in chroma and lightness; the chroma seems to vary with pigment particle size and somewhat with pigment density.

The main drawback to this pigment is its dense opacity. The solution is to dilute the paint and use it as a tint wash, or add it in small quantities to color mixtures. It is extremely effective at warming sap green and yellow mixtures, subduing intense yellow, orange or red paints, neutralizing blue and cyan paints, and producing a wonderful range of salmon, pinkish and pale flesh tints. Winslow Homer's favorite black was mixed with venetian red and iron blue; it makes fabulous sky grays when added to cobalt blue. I urge you to try it and apply it as delicately as you are able: the results may surprise you!

Typically indian red is a darker, more opaque and slightly warmer paint than venetian red, with an almost purplish color when applied full strength.

Red ochre is an older alternative term for calcined iron oxide, which was often so dull it appeared brown.

• QUINACRIDONE MAROON (PR206). As with quinacridone gold, the coloristics of quinacridone maroon are very similar across manufacturers. This is one of the reddest "earth" pigments, and makes an interesting, transparent and more saturated alternative to both burnt sienna and venetian red (mars red). It is especially effective at neutralizing (desaturating) paints from iron blue to viridian — over one fourth the color circle! (See the page on watercolor mixing complements.)

• MARS VIOLET. An infrequently used earth color, usually much darker and slightly redder than mars red (venetian red). Few manufacturers make it, and as you can see, their paints are very similar. Note that the apparent hue shift toward violet is caused simply by darkening the red iron oxide color; all masstone red and red violet pigments seem to shift toward purple as chroma or lightness decreases. (Utrecht's venetian red is so dark and purplish it can easily pass for mars violet in some contexts.) In contrast, as tints the paints appear almost pinkish.

• SEPIA. Often the closest color to black among the "earth" colors in a watercolor line. Sepia was originally a pigment produced from the ink of cuttlefish, and widely used in writing inks. The modern (more lightfast) substitutes are usually made by mixing a dark iron oxide with carbon black. Some brands of van dyke brown have a similar blackish brown color.

The Earth Quintet. Raw sienna (or yellow ochre), raw umber, burnt sienna, burnt umber and venetian red form an "earth quintet" of paints that are usually designed as a group by paint manufactuers. By connecting together the earth color markers for the same manufacturer, you can identify the "brand style" of each paint company's earth palette.

Winsor & Newton, Maimeri and Rembrandt prefer a relatively saturated, widely separated palette of colors, Daniel Smith and M. Graham design their colors to be darker and more subdued. These differences don't reflect the quality of the pigments used, but the overall color design the manufacturers aim for in their complete paint line.

 

Last revised 08.17.2007 • © 2007 Bruce MacEvoy

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