Earth Pigments

Part of Pigments and Paint

Finding, collecting, and processing earth pigments — the most accessible, permanent, and historically important class of pigments.

Why This Matters

Earth pigments are the oldest and most reliable colorants known to humanity. The red and yellow ochres on the cave walls of Lascaux, Altamira, and Chauvet are 15,000 to 40,000 years old and remain vibrant. No synthetic pigment can match this track record. Earth pigments are permanent, lightfast, non-toxic, chemically stable, and compatible with every binder system. They are also free — sitting in the ground, waiting to be collected.

For a rebuilding community, earth pigments are the foundation of all color work. They provide the yellows, reds, oranges, browns, and greens needed for paint, ink, dye mordants, ceramics glazes, and cosmetics. A community that identifies and processes its local earth pigments has a permanent, inexhaustible supply of colorants that require no trade, no chemistry, and no specialized equipment to produce.

The skill of reading the landscape for pigment deposits also teaches valuable geological literacy. The same iron minerals that create ochre deposits indicate soil chemistry relevant to agriculture, water quality, and mineral resources. Learning to find earth pigments is a gateway to broader geological awareness.

What Earth Pigments Are

Chemistry

Earth pigments get their color primarily from iron oxide and iron hydroxide minerals:

Mineral	Chemical Formula	Color	Pigment Name
Goethite	FeOOH	Yellow to brown	Yellow ochre, raw sienna
Hematite	Fe2O3	Red to maroon	Red ochre, Indian red
Limonite	FeOOH + water	Yellow-brown	Limonite, raw umber
Magnetite	Fe3O4	Black	Natural black iron oxide
Glauconite	Complex silicate	Green	Green earth, terre verte
Manganese dioxide	MnO2	Brown-black	Raw umber (contributes brown)

The color of any earth pigment depends on three factors:

1. Which iron mineral is present (goethite = yellow, hematite = red)
2. The particle size of the mineral (finer = more vivid)
3. What other minerals are mixed in (manganese darkens, clay lightens, silica dilutes)

The Earth Pigment Palette

Pigment	Color	Found As
Yellow ochre	Golden yellow to mustard	Soft clay deposits, stream banks
Raw sienna	Transparent warm yellow-brown	Named after Siena, Italy; found widely
Red ochre	Warm red to maroon	Exposed rock, red-stained clay
Burnt sienna	Rich reddish-brown	Calcined raw sienna
Raw umber	Cool greenish-brown	Deposits rich in manganese + iron
Burnt umber	Deep warm brown	Calcined raw umber
Green earth (terre verte)	Muted olive-green	Specific geological formations
Natural black oxide	Dense black	Rare; found near volcanic areas

Finding Earth Pigments

Where to Look

Earth pigments concentrate where geological processes have deposited iron minerals:

River banks and stream cuts — the most productive prospecting locations. Running water erodes banks, exposing colored strata. Walk along stream banks looking for:

• Yellow, orange, or red bands in the exposed soil profile
• Colored sediment deposited at the waterline
• Stained rocks and gravel

Exposed rock faces — road cuts, cliff faces, quarries, and naturally eroded slopes reveal colored mineral layers. Look for:

• Horizontal bands of color in layered sedimentary rock
• Red or yellow staining on rock surfaces
• Seep points where iron-rich water emerges and deposits color

Bog and marsh edges — iron-rich water creates “bog iron” deposits that include excellent yellow and orange pigments:

• Look for orange-brown staining in standing water
• Iridescent oil-like films on bog water (actually iron oxide)
• Crusty orange deposits on rocks and debris in iron-rich streams

Around springs — mineral springs often deposit colored minerals where the water surfaces. These deposits can be thick and pure.

Agricultural fields — after plowing, look for patches of strongly colored soil. Red or yellow patches in otherwise brown fields indicate concentrated iron minerals.

Prospecting Method

1. Walk and observe — cover ground slowly, looking at every exposed earth surface
2. Carry a knife — scrape exposed surfaces to see the true color beneath weathered crusts
3. Finger test — rub a suspected pigment between your fingers. Good earth pigment produces a smooth, strongly colored smear. Sandy or gritty material is too dilute.
4. Streak test — drag the material across a white surface (a piece of pottery, bone, or light stone). The streak reveals the true color.
5. Collect samples — bring back samples from every promising location. A handful is enough to test.
6. Map your sources — record the location of every good deposit for future harvesting

Color Variety

A single river bank may contain yellow ochre, orange ochre, red ochre, and brown umber in different strata within a few meters. Always explore the full vertical profile — do not stop at the first color you find.

Processing Earth Pigments

Step 1: Harvesting

1. Dig or scrape raw earth from the deposit
2. Remove obvious contaminants — roots, rocks, leaves, insects
3. Collect more than you think you need — processing reduces volume significantly
4. Transport in cloth bags, baskets, or ceramic containers

Step 2: Drying

1. Spread raw earth on a clean, flat surface (a wooden board, flat stone, or cloth)
2. Break up large lumps with your hands
3. Dry in the sun for 1-3 days, turning occasionally
4. Fully dry pigment is easier to grind and stores better

Step 3: Crushing

1. Break dried lumps into coarse powder using a mortar and pestle, or by pounding in a wooden bowl
2. Remove any remaining non-pigment debris (stones, roots, sand grains) by hand-picking or sieving

Step 4: Washing (Levigation)

This is the most important processing step. It separates fine pigment particles from coarse sand, silt, and debris:

1. Place crushed pigment in a large container (bucket, pot, or wooden trough)
2. Add water — approximately 5-10 times the volume of the pigment
3. Stir vigorously for 1-2 minutes
4. Wait 30 seconds — heavy sand and coarse particles settle to the bottom
5. Pour off the colored water into a second container, leaving the settled coarse material behind
6. Wait again — in the second container, let the pigment settle for 2-4 hours (or overnight for the finest fraction)
7. Pour off clear water from the top
8. Collect the settled pigment — this is your refined earth pigment

Grading by Particle Size

You can separate pigment into quality grades by adjusting settling time:

Settling Time	Particle Grade	Use
Settles in under 30 seconds	Coarse — discard or re-grind	Too gritty for paint
Settles in 30 seconds - 5 minutes	Medium — usable for rough paint	Exterior coatings, whitewash tinting
Settles in 5 minutes - 2 hours	Fine — good quality	General-purpose paint and ink
Settles in 2-24 hours	Very fine — premium quality	Fine painting, manuscripts, calligraphy ink
Remains suspended after 24 hours	Ultra-fine — highest quality	Glazing, watercolor, finest work

Step 5: Drying and Storage

1. Spread the settled pigment on a clean surface to dry (ceramic plate, wooden board, or cloth)
2. Dry in shade — direct sun does not damage earth pigments but may bake the surface into hard lumps
3. Once dry, crumble any lumps and store in sealed containers
4. Label with color, source location, and date collected
5. Earth pigments store indefinitely — there is no shelf life

Step 6: Final Grinding (Mulling)

Before use in paint, grind the dried pigment to its final fineness:

1. Place a small mound of dry pigment on a flat stone slab (granite, marble, or thick glass)
2. Add a few drops of binder (gum arabic solution, oil, or egg tempera medium)
3. Use a muller — a smooth, flat-bottomed stone that fits in your palm — to grind the pigment into the binder with firm, circular motions
4. Continue mulling for 15-30 minutes until the mixture is perfectly smooth
5. Test by drawing a thin stripe across a white surface — it should be even and streak-free

Modifying Earth Pigments

Calcination (Heat Treatment)

Heating earth pigments changes their color by converting iron hydroxides to iron oxides:

Starting Pigment	Heat Treatment	Result
Yellow ochre	300-500 C, 1-2 hours	Red ochre (warm orange-red)
Raw sienna	300-500 C, 1-2 hours	Burnt sienna (rich reddish-brown)
Raw umber	400-600 C, 1-2 hours	Burnt umber (deep warm brown)
Light yellow ochre	200-300 C, 30 minutes	Deepened to golden orange

This is the single most useful pigment modification technique. From one yellow ochre deposit, you can produce the full range from golden yellow through orange to deep red simply by controlling the calcination temperature. See Calcination for detailed process instructions.

Mixing Earth Pigments

Earth pigments mix freely with each other and with most other pigments:

Mixture	Result
Yellow ochre + white	Cream, buff, light gold
Red ochre + white	Pink, rose, salmon
Raw umber + white	Warm gray, stone color
Yellow ochre + red ochre	Orange, terracotta
Yellow ochre + black	Olive green
Red ochre + black	Maroon, chocolate
Raw umber + yellow ochre	Warm golden brown

Enrichment

If a natural deposit is too weak (too much clay or sand, not enough iron mineral), you can concentrate it:

1. Perform multiple rounds of levigation
2. Each round, discard the coarse fraction (mostly sand/clay)
3. The fine fraction becomes progressively more concentrated with iron mineral
4. After 3-4 rounds, even a weak deposit can yield usable pigment

Earth Pigments by Color

Yellows

Yellow ochre — the most common and most useful earth pigment. Found worldwide wherever iron hydroxide (goethite) has accumulated in clay deposits. Ranges from pale lemon-yellow to deep mustard depending on iron concentration and purity. Use for: wall paint, signage, mixing with blue for green, tinting white for cream.

Reds

Red ochre — either found naturally (exposed hematite deposits) or made by calcining yellow ochre. The most permanent red pigment available without advanced chemistry. Ranges from warm orange-red to deep maroon. Use for: safety markings, decorative paint, mixing with blue for purple-brown, tinting.

Browns

Raw umber — distinguished from plain ochre by its manganese content, which gives it a cooler, greenish-brown tone. Found less commonly than ochre but still widespread. Burnt umber (calcined raw umber) is a deep, warm brown that is the standard shadowing color in painting.

Raw sienna — a particularly transparent yellow-brown ochre, prized for its glazing quality when used in thin layers over other colors.

Greens

Green earth (terre verte) — the only true green earth pigment. Colored by glauconite or celadonite minerals. Less common than ochres but found in specific geological formations (marine sedimentary deposits). A muted, olive-green that is weak in tinting strength but invaluable as a green since true green pigments are rare in nature.

Finding Green Earth

Green earth deposits are less obvious than ochres because the green color is subtle and can be mistaken for ordinary gray or dark soil. If you find a soft, slightly waxy or soapy-feeling earth with a green-gray color, test it — grind a sample with oil on a white surface. If it produces a noticeable green, you have found a valuable pigment source.

Blacks

Natural black iron oxide (magnetite) is found but is rarely pure enough for pigment use. For black pigments, carbon sources (lampblack, charcoal, bone black) are more practical and produce better results. See Carbon Pigments.

Quality Assessment

Test your processed earth pigments before committing them to important work:

Test	Good Pigment	Poor Pigment
Finger feel	Silky smooth, no grittiness	Sandy, scratchy
Streak on white surface	Strong, even color	Weak, streaky
Tinting strength	Small amount visibly colors white paint	Needs large amount to show color
Drying behavior	Dries to consistent color	Patchy, separates
Lightfastness	No change after weeks in sunlight	Fades or shifts (rare for earth pigments)
Compatibility	Mixes smoothly with all binders	Clumps, separates, or reacts

Earth pigments that pass these tests are ready for any application — from rough exterior house paint to fine manuscript illumination.