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Yellow ochre is an earthy yellow pigment that has been used in painting for centuries. Ochre comes from naturally occurring iron oxide-rich clay deposits and it gets its yellow color from hydrated iron oxide. The specific combination of clays, minerals and iron oxide present determines the exact hue of the ochre. While natural yellow ochre varies in shade, the most common form is a dull yellow. Understanding what two colors make yellow ochre helps explain its characteristics and origins.
Primary Pigments in Yellow Ochre
There are two primary pigments that create the yellow ochre color when combined:
Yellow Iron Oxide
Also known as yellow iron hydroxide or limonite, yellow iron oxide provides the distinctive yellow hue in yellow ochre. It is formed when iron oxidation occurs in the presence of water, producing the chemical compound iron(III) oxide-hydroxide. This mineral pigment ranges from a light lemon yellow to a darker mustard brownish-yellow. The amount and hydration level of the iron oxide particles affect the saturation of the yellow color. Higher hydrated forms with smaller particle size produce more vibrant yellows.
Clay
Clay is the second essential component in yellow ochre. The clay acts as a base that absorbs the yellow iron oxide pigment particles. Common clays used include kaolin and bentonite. The clay’s natural color is white to grey when pure, but takes on a yellowish or reddish tint when iron oxide is present. The type of clay influences the ochre’s texture and shade. Lighter clays produce brighter yellow ochres. Darker clays create more muted, olive-toned ochres. The clay’s absorption properties also affect the depth of shade. More loosely packed clay results in a weaker, paler color.
How Yellow Iron Oxide and Clay Create Yellow Ochre
On their own, yellow iron oxide and white-grey clay have colors distinct from yellow ochre. But when these two pigments combine in nature they produce the characteristic soft yellow hue of ochre. Here is how the ingredients work together:
Iron Oxide Pigment Particles are Absorbed by Clay
Natural yellow ochre forms over long time periods as iron oxide particles are deposited into clay deposits. As the clay absorbs the iron oxide particles, its color changes from greyish to yellowish. The clay acts as a binder and support for the pigment. Different clays have different particle sizes and absorption capacities, resulting in varied color saturation.
Complementary Colors Produce Olive-Yellow Hues
When complementary colors combine, they neutralize each other to create muted, olive-yellow ochre tones. The yellow iron oxide pigment is the complementary color of the white-blue based clay. This explains why ochre is not a pure, bright yellow but rather a more subdued, olive-leaning shade. The saturation of the yellow depends on the relative amounts of the two pigments present.
Chemical Composition Influences Color Quality
The exact chemical composition of the ingredients impacts the final ochre color. Iron oxide’s hydration level, particle size, and purity affect its yellowness. Impurities in the clay also modify the color. Higher fired clays produce deeper, reddish ochres. The mineral makeup combined with the absorption and binding properties of the clay and iron oxide work together to create yellow ochre’s characteristic color.
Characteristics of Yellow Ochre Pigment
Understanding the relationship between iron oxide and clay helps explain the common properties found in yellow ochre pigment:
Earthy Yellow-Orange Tone
Yellow ochre has a soft, muted, earthy color ranging from pale lemon yellow to richer golden orange-yellow. The iron oxide pigment combined with light grey clay base produces this subdued olive-yellow tone. The clay moderates the vibrancy of the yellow iron oxide.
Semi-Transparent Optical Effects
Natural yellow ochres allow some light to pass through due to the semi-transparent iron oxide particles suspended in the clay base. This creates optical color blending effects on the canvas. Layers of ochre mixed together produce more natural shading than pure opaque colors.
Absorption Affects Color Intensity
Because ochre pigment relies on the absorption properties of clay, the color intensity varies. Loose, porous clays result in weaker earth tones. Densely packed clays allow deeper, stronger yellow ochre coloring. Particle size also affects saturation, with finer particles absorbing more densely.
Matt Texture
Yellow ochre paint has a characteristically matt, flat finish. The clay base provides soft texture and helps absorb excess oil from oil paintings. The earthy mineral pigment provides subtle texture effects.
Semi-Permanent Tinting Strength
Natural yellow ochre has moderate tinting strength and lightfastness. The iron oxide pigments are more permanent and coloring than the clay base itself. With oil binders, the ochre can fade to paler shades over decades but still retains its essential yellowish character.
Types of Yellow Ochre Pigment
While all authentic ochres contain iron oxide and clay, the variety of mineral sources results in a range of yellow ochre shades and properties. Here are some common varieties:
French Ochre
French ochres are highly prized for their color quality. They contain yellow iron oxide pigments in kaolinite clays, resulting in clear, bright yellows ranging from lemon to deep gold. French ochre offers excellent coverage and tinting strength.
Italian Ochre
Italian ochres use iron-rich clay sources like limonite, producing deeper, warmer golden yellow tones. Increased iron oxide content provides high tinting strength. Italian ochre is valued for its bold coloring.
Indian Yellow Ochre
Indian ochres derive their rich golden hue from goethite iron oxide pigments. Indian yellow ochre is one of the strongest coloring ochres due to its high pigment content and deep color. It has excellent hiding power.
English Ochre
Ochres from the clay deposits in Oxford and Devon, England offer soft, muted yellow tones. Less hydrated iron oxide paired with kaolinite clays create mellow, olive-inflected yellows. English ochres have moderate tinting strength.
American Yellow Ochre
Domestic ochre sources in the Eastern United States contain iron oxide pigments paired with bentonite or fuller’s earth clays. They produce subdued greenish-yellow shades with lower tinting strength than European varieties.
Uses of Yellow Ochre Pigment in Painting
Yellow ochre has served many uses in oil and watercolor painting historically thanks to its versatile properties:
Glazing and Washes
The transparent qualities of yellow ochre make it ideal for glazing over other colors to shift a tone warmer or for transparent washes. Ochre creates a luminous glow in diluted paint.
Underpainting
As an initial underpainting layer, yellow ochre provides a lively colored ground that brings vibrancy to layers painted on top. The absorption of the ochre helps sinking in of upper paint.
Flesh Tones and Skintones
Mixed with white and red pigments, yellow ochre creates flesh tone colors from fair to ruddy. Its transparency helps mimic skin’s appearance.
Earth Tones and Foliage
On its own or mixed with umber, yellow ochre realistically depicts the colors of the natural landscape in earth, grasses, plants and rocks.
Warming Other Pigments
Added to any color, yellow ochre warms and enlivens the tone. It’s useful for modifying greens, oranges, browns, purples, reds and more.
Depth and Texture
The inherent texture of natural ochre provides depth and natural optic blending ideal for realist painting. Ochre’s richness under oil paint gives canvas luminosity.
Conclusion
Yellow ochre derives its characteristic dusty, olive-toned yellow color from the combination of two primary pigments – yellow iron oxide and white clay. It is the absorption of transparent yellow iron oxide particles into the complementary grey clay base that produces the distinctive soft, earthy yellow shades. Understanding ochre’s chemical composition helps explain its common qualities of semi-transparency, matt texture, and subdued earth tones. This makes natural yellow ochre invaluable for its uses in glazing, flesh painting, and building depth and realism in oil and watercolor works to emulate the vibrancy found in nature.
