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Earth Pigments in the Landscape 

There are sources of naturally occurring iron rich minerals all over the world. Ochre pigments contain mostly the inorganic content of the earth. We are looking for places where there is little organic soil, or decomposing plant material. There are many different forms that the mineral sources of iron oxide can come in. We are looking for the brightest colours, where the starting material is as soft and crumbly as possible. Geologists use the term ‘ocherous’ to refer specifically to the red, orange, yellow or brown hues of iron containing minerals within a geological context that have particularly low harness on the mohs scale and exhibit soft textures. This description is usually used in reference to the discussion of sedimentary rocks, soils or deposits influenced by iron oxidation giving them their characteristic colours. 

Some points to consider before gathering raw material

Start with a soft raw material sample:

• This limits the amount of physical labour and time we have to do to break it down into a fine powder.

• Rocks that contain aluminum silicate minerals will destaurate on particle reduction.

• Rocks that contain silica create incredibly fine airborne particles that once breathed in do not leave the lungs and contribute towards silicosis, an avoidable degenerate and cumulative disease. 

• By removing material that will provide us with bright usable pigments, we can avoid taking more than what we need. 

Research

You can visit a site or stumble upon one with no prior knowledge of the sites’; geology, history, ecology and land ownership. If you want to be better informed before the removal of material has begun, preempt any issues or problems relating to repatriation later on there are some ethical standpoints to consider (see Foraging Intent & Reciprocity). Research can take many forms, to learn about a site perhaps consider:

Primary research 

• Talk to local people, especially those who know the land intimately. 

• Native or indigenous peoples of that land should be acknowledged and permission sought from.

• Find someone who has a long standing relationship with the site and ask for them to accompany you. This could be individuals or organisations that relate to the local history, ecology,  geology  of the site.

• Experience the place first without sample removal.

Secondary Research

• Use local libraries or council town record offices to find out more about the socio-politics of the space.

• Look through the local geological surveys to pinpoint safety issues and any abundance of iron or iron ore deposits.

• Check the laws both regionally and nationally to see if you may collect there. Sometimes these laws or by-laws contradict each other.

Types of Iron Oxide Mineral Sources for Pigment Making:

Clay

Clay is a complex material made of a mixture of fine-grained clay minerals, usually less than 2 microns small. It forms from the weathering of silicate minerals over long expanses of time. The breaking down of these minerals due to physical and chemical erosion (such as temperature changes, water and biological activity) contributes towards a key part of the Earth’s rock cycle. Clay particles swell when mixed with water to create a malleable and moldable substance with great plasticity. Types of clay include kaolinite, illite, smectite, chlorite, vermiculite, attapulgite and sepiolite. These clay types will vary in particle size, structure, plasticity, and shrinkage. Clays that contain high quantities of iron and little sand will be useful for pigment making.

Iron Ore Minerals

Iron ore minerals usually have an iron content of over 50% or more and this makes them incredibly hard, dense and sometimes have a metallic sheen. These generous sources of iron oxide will create luminous shades of red and orange when ground finely. They will vary in hardness depending on how weathered and oxidised they are and can be found in lump form within or nearby clay bodies. The best sources of natural ochres are rocks and minerals that are rich in iron oxides and hydroxides. 

Hematite (Fe₂O₃)

Found commonly in sedimentary, metamorphic and igneous rocks, hematite is the richest source of iron oxide for pigment making, composed of over 69% iron. It will produce luminous red pigments, when found either pure or mixed with other clay bodies or within rock formations. Iron staining caused by Hematite is often referred to as red ochre. Forming from the oxidation of iron-bearing minerals in a variety of geological settings, including weathered iron-rich rocks and hydrothermal deposits. It can be found globally with substantial deposits in Brazil, Australia and parts of the U.S.

Goethite (FeO(OH))

Goethite is a major source of natural yellow ochre. It is a hydrous iron oxide mineral that forms in low-temperature, oxidizing environments. It produces yellow to brown pigments, typically yellow ochre. Goethite forms through the weathering of iron-rich minerals and is often found in soils, bogs, and gossan formations (oxidized portions of ore deposits). Goethite is found worldwide, with significant deposits in France, Spain, and the U.S.

Limonite FeO(OH)·nH₂O)

Limonite is a mixture of hydrous iron oxides and is another source of yellow and brown ochres. It forms in weathering environments, often alongside goethite. It ranges from yellow to brown, providing earthy tones. Limonite is typically a weathering product of iron-rich minerals such as pyrite or siderite. Major deposits of limonite are found in places like Italy, France, and the U.S. Goethite has been referred to historically as limonite and these two names continue to be used interchangeably. 

Magnetite (Fe₃O₄)

Magnetite is an iron oxide mineral that, when oxidized, can produce pigments, although it is more often associated with black or dark-colored materials. Magnetite produces darker shades, but with oxidation, it can lead to pigments similar to those from hematite. It forms in igneous and metamorphic rocks and is found in beach sands or as a residual mineral from weathering. Magnetite is found globally, with major deposits in Australia, South Africa, and the U.S.

Pyrite (FeS₂)

Pyrite can indirectly serve as a source of iron oxide through the process of weathering or oxidation. Although pyrite itself is an iron sulfide, when exposed to oxygen and water over time, it undergoes chemical weathering, which produces iron oxides such as hematite (Fe₂O₃) and goethite (FeO(OH)), along with other byproducts like sulfuric acid. When pyrite is exposed to oxygen and moisture, it reacts to form ferric iron (Fe³⁺) and sulfate (SO₄²⁻). This ferric iron can precipitate as iron oxide minerals like goethite or hematite. The oxidation of pyrite results in the production of iron oxides that contribute to the reddish or yellowish color often observed in weathered rocks and soils. This process is common in gossans, the rust-colored caps formed over sulfide ore bodies as a result of the oxidation of minerals like pyrite. Pyrite oxidation is a major process in the formation of acid mine drainage where the sulfuric acid produced can cause environmental damage. However, it also leads to the deposition of iron oxides in areas like riverbeds and soils, contributing to ochre formations.

Ochreous Soils, sands and Sediments

Ochreous soils are rich in iron oxides, particularly in regions where iron-rich rocks have weathered over time. These soils are often collected directly as sources for ochre pigments. Depending on the specific iron oxide content, these soils can be yellow, red, or brown.These ochre-rich soils are found in many regions, including southern Europe, Australia, and parts of Africa.

Pyrolusite (MnO₂)

Though not strictly an iron oxide, pyrolusite can be used for dark pigments, often as a black or gray addition to ochre mixtures. Pyrolusite contributes to dark pigments. It forms through the oxidation of manganese-bearing minerals, often associated with iron oxides. As it has an affinity for iron it often contributes towards a rich brown leaning in darker earth pigment mixes. It is found in South Africa, India, Russia and the U.S.

Foraging Intent & reciprocity

The removal of material for use in your practice is extractive albeit a small intervention in scale upon your geological locale. Roughly 120 million tons of clay are mined globally each year by industry.  However with the rising trend of using wild clay within creative practices for ceramists, sculptors and pigment makers these volumes are not accounted for within annual statistics. The direct nature of taking from wild sources of clay is useful in giving us a visual representation of one of the actions we take that affects the natural world. We can use this as a meditative and therapeutic action. When taking and profiting creatively from a place there are many ways in which we can generously give back. The creation of weathered mineral sources is part of  larger geological and ecological processes and so seeing the specific clay material and your own personal collecting as isolated is detrimental. 

We could consider:

• Collecting human-made rubbish from the site. 

• Consider positively intervening with some local plant husbandry such as helping to spread seed, mulching and pruning for growth. 

• Learn about your local ecology and share what you’ve learned with those who live near you to inspire others to continue their own relationship to the natural world.

• Create awareness about foraging techniques through education and workshops.

• Developing ecology at home by broadening and enriching the ecosystems in your garden. 

• Donate to charity and organisations that relate to the space.

• Take children to forest school and introduce them to your practice. 

• Support disadvantaged people to have access to the space and introduce them to your practice.

• Support indigenous and native peoples who live on the land.

Place 

What is the logic behind our connection to place? What does connecting to place mean? And why is it important? We can connect to a place through the interaction of collecting found materials, which brings about familiarity with the local landscape. This plays out over time to become intimacy. To fully explore a location through pigment making we become more present within the space. When we become more present we become more alert and alive. We create feelings associated with that space and those feelings make us human or more human. So by utilising found local materials it can make us feel more and bring about a therapeutic relationship to colour.  Colour is therapeutic in its own right as joyful simulacra and stimulation is optical joy. So what if those colours also have underlying connections to place? These are powerful strands that start to form. This leads us to want to protect these spaces.

Processing pigment is like human weathering: speeding up erosion or time

The pigment studio as a time vacuum

Exposure, Erosure

Breaking down, returning to building blocks 

Land Ownership 

If you can, before gathering ochre pigments from your locale do some research about the history of the spaces you will be frequenting. 

• Is the land held as significant to indigenous or religious communities 

• Are there stakes to the land made by different groups of people? 

• Is the land privately owned or common land?

• Is the site under any state of ecological preservation? Is it a Site of Scientific Interest (SSI) or a nature reserve?

• Is the land used for hunting?

Safety 

Be mindful of heavy metals and radioactive minerals. If there has been some history of mining on the land there may be areas of contamination or spoil heaps, or uneven ground likely to collapse. If you're collecting by a water source, locate any safety measures in place and take note of tidal movements. Wear protective equipment such as gloves and a respirator if material is loose and dusty. Bring a geiger counter if the area is a known area of radioactive contamination. 

Topographical features to look out for:

Look out for colour in unexpected places

• Bare, exposed earth, areas not covered in vegetation or built upon

• Human interventions: quarries, mines road cuts,construction sites 

• Water sources: banks of rivers, streams, lakes, seas, dams

• Natural geological features that reveal swathes of deep time: cliffs, hills, mountains 

Processing earths steps

In Situ

1.Choose

Once you have considered the ethics of removing material outlined above. Select your rock, a quantity of loose earth or clay.

Reasons for choices may include: brightness, clarity, minimum amount of impurities, personal context etc

Be open to possibilities of colour appearing in your daily life. Develop a consciousness of the ground beneath you and an understanding of the geology that you live upon. 

TIP: Colours of different earths in situ can be misleading. Often colour looks brighter in its original context against vivid green foliage or can look darker if moist. One can get excited about the brightness of a hue only to return to the studio with a bag full of grey dull soil. 

TIP: Bring some sandpaper with you to test the hardness of the material and it's a quick way to gauge the resulting colour of the sample once ground finely. Wet the sample with some water and see if any colour can be removed with a brush, if it can this is a good indication of its potential for pigment.

2. Collect

Tools

Rubber gloves

Trowel, shovel, spoon, scoop

Bags for samples (waxed cotton, reusable plastic etc)

Wearing gloves, using a trowel, collapsible army shovel or make-do with a spoon or cut a plastic bottle into a scoop, collect your sample. If you can locate fallen rocks or disturbed material be mindful to use these as their use will have a  lower impact upon the site. If you can do some preprocessing on site such as the removal of small stones and organic material like leaves, twigs etc then that will be less to travel with and less impact made on the location. Use a reusable sample bag, this could be made of waxed cotton or a plastic zip lock bag. Note the GPS location, date and description of the place. 

Back at home or in the studio:

3. Sort

Tools

Garden sieve/riddle 

Rubber gloves

Receptacles (Bucket, paint kettle, bucket)

Kitchen sieve

Dry Sample :

Remove unwanted material from the sample by hand or by using a coarse garden sieve or riddle (garden sieve) with 10 mm square holes. Do this by putting large handfuls of your sample into the riddle over a receptacle that is at least 5 cm larger in diameter (to catch all of the material when agitating the riddle). You may need to break the sample up with your hands if it has clumped together. The stones and plant material caught in the riddle can be put in a garden or brought back to the site.

Wet soil or clay sample:

Put the sample into a bucket or similar receptacle and add water until a slurry is produced. Some plant material may float to the surface- if it does this can be removed by hand or with a kitchen sieve it can be scooped and put to one side. 

Now it can be put through a riddle as above. 

This step will remove the following:

Inorganic material - any large stones, aggregate, 

Organic material - dried or fresh - twigs, leaves, roots

Living organisms - Be careful to attend to insects that may be in your sample that can be removed and put outside in a favorable place. 

TIP: If sourcing colour from found material like brick, then dust mud or dirt from them using a coarse brush

Organic impurities will contribute towards an unstable paint film and could lead to cracking of the painting’s surface.

Crush

Tools

Safety goggles, rubber gloves respirator 

Strong hessian, thick plastic/canvas bag 

Metal mallet/hammer

Receptacles (Bucket, paint kettle, bucket)

If the sample is dry and hard we need to reduce the particle size to be able to take it to the next stage of washing.

Break down material into small pieces:

• Wear safety goggles, gloves and a respirator.

• Put the material in a strong hessian sack/thick plastic/canvas bag (double bag the sample) and hit it with a mallet until you are  left with pieces that are less than 5 mm in diameter, less than a pea size. 

Grade

• At this point it is possible to remove some pieces that are darker or have inclusions in. Separate any differences in colour by dividing up the batch, this is done by hand, picking out the various pieces by hand. 

• For example, Georgian yellow brick has rather large dark masses in the brick that I try to remove as they make the resulting pigment duller.

Grind

Tools

Pestle and mortar

Electric coffee grinder

Hand driven/ electric grain crusher/ flour machine

Ball mill

• Put all of the material, which by now is a mixture of fine and coarse dust into a pestle and mortar or electric coffee grinder (put aside for this use). A hand-driven grain grinder can also be utilised. At the L. Cornelissen & son, in the pigment warehouse, they break down gums like gum damar using this kind of machinery. They use an antique grain grinder as it doesn’t heat the gum up too much otherwise it would all stick together. 

• Depending on the material, using the grinder to break down lumps can take a few minutes to many more. A ball mill can be used for large batches of material for particularly hard rubble.

Wash

Tools

Receptacles (Bucket, paint kettle, bucket)

Distilled water

Ph indicator paper

• The material (such as clay or ochre) is mixed with water to form a slurry. Pour the dust carefully into large plastic containers and mix it with lots of tap water, mix well with gloved hands or a wooden stirrer. 

• Wait for the particles to settle to the bottom of the container and pour away the excess water, soluble impurities like metal salts and organic resins, tars (such as asphalt) can be removed this way. An indication of impurities in your water is a distinctive white, grey or pale yellow foam and an unclear solution once settled.

• Repeat this step until the water that separates is crystal clear. Samples will vary in how much washing they will need, the minimum is usually around 5 times. 

• The last 2 washes should be done in rain, filtered, or better yet, distilled water. 

• Test the last water to be poured off for its Ph, using Ph indicator paper. If not neutral, continue washing steps. 

Key Term: Leachate- Solution of contaminants that have leached out into the water that will be removed.

TIP

If you suspect that there are soluble forms of iron in an accessible water source or in the water jettisoned from your washed sample it might be able to be converted into pigment. Experiment to see if ochre can be made. Iron can be precipitated out of suspension by altering the pH of the solution by the addition of an alkali, lime or chalk would work well.

A field guide to working with and for ochre 

Pigments are not abstracted from their original context, they ARE their context. Whilst processing your sample it could be useful to think about the interplay of ochres past uses, chemical, medicinal, remedial, ritualistic. These aspects form a space as a progressive research field that could bring about new understanding relating to new applications within this broad polychromatic subject area. 

Living beings accumulate minerals and elements within their bodies, which through decay return to the earth. We are a part of these infinite cycles of decay and regeneration. Our bodies are composed of minerals with sentience, living stones, ourselves living alongside and with complex bacterial life. Our bodies can be considered as vehicles capable of growing rocks. We have kidney stones growing in our bodies when there is a surplus of calcium, oxalate, or uric acid, which causes these materials to crystalise into solid structures. This contracts the distance between our material differences, and we seem closer to them, as we have a common ability to grow, crystalise, and sediment. The body is a living temple, alive with ochre. The body is a pulsating, moving, being, internally iron moves, and externally iron is moving within the landscape. We are ochre accumulators, and biological ochre factories. Living ochre caves, transforming with the moons’ cycles. Ochre could be used as a compass, a lens, a  material archetype that can be used to navigate the world. The human body is mostly composed of cosmic dust brought to the earth through stars dyeing. Our position within the scale of deep time is not linear, but made of the most complex web. We contain materials that could create a new chromosphere, a chromascape.

Abstracting Ochre 

When we process raw earth into usable ochre pigments we have unattached the material from its home and the material it once related to. In the removal of matter that we consider as ‘impurities’ or materials that are ‘in the way’, obscuring the chromatic purity of the colour we reveal or embolden characteristics of the rock or clay. Now the ochre is more unattached, removed from its context, controlled, contained, reduced to mere optical qualities. Abstracted and dematerialised we make it yield to our desired applications.

The ochre is then further contained by its admixture with a glue, squished into a paint tube, homogenised in a paint range. There is a special potentiality in the untouched vial of pigment colour, its qualities yet to be revealed through use with different binders, fillers or extended, or techniques. In this way I see the processing of colour as performing nature into culture. In the studio or workshop we speed up time, we erode and breakdown material in an instant that would take rivers and seas hundreds of years to do. In the vacuum of the creative space, creative destructive forces enact natural environmental phenomena.

Levigation 

Levigation is a process used to purify and refine materials, particularly clays and other earths, by suspending them in water and allowing the heavier, unwanted particles (such as sand or grit) to settle out, while the finer particles remain suspended. The term is derived from the Latin word levigare, meaning ‘to make smooth’ or ‘to polish’.This is a process that creates different grades of the sample, often resulting in differing shades of colour. This is a result of varying grain sizes of the pigment. In the context of earth materials, levigation refers specifically to the separation of finer, iron oxide, clay or pigment particles from coarser ones. It is commonly used in industries dealing with ceramics, pottery, pigments, and even cosmetics, where fine, homogeneous particles are desired for better texture and consistency.

Levigation is a simple but effective method for refining earth materials by separating finer particles from coarser ones. This technique has been used for thousands of years in various industries, including ceramics, pigment production, and cosmetics, to ensure a smooth, consistent product.In ancient Egypt and other early civilizations, levigation was commonly used to prepare fine pigments from natural minerals and earths. Artists would levigate ochre or malachite to create high-quality pigments for painting. The same technique is still used today in the traditional craft of pigment making, ensuring that the materials are of the finest possible quality for use in paint, ceramics, and other products.

The Levigation Process

Method 1: 

Tools

Receptacles (bucket, paint kettle, bucket)

1. Suspension in Water: 

With a washed mineral sample, make sure that all clumps of material are broken up and fully suspend the finer particles in the water to form a homogenous slurry. Agitate the solution so that the fine particles are in suspension. 

TIP: Allow your washed sample to dry fully before levigating. It will absorb the added water very quickly to form a homogeneous slurry, much quicker than a medium wet sample.

2. Separation by Settling: The suspension is then allowed to stand undisturbed for a few minutes. Heavier and coarser particles, such as grit or sand, settle at the bottom of the container due to gravity.

3. Decantation: The finer particles, which remain suspended in the upper layers of the water, are carefully decanted or siphoned off. Carefully tip the vessel and pour the water containing the finest particles into a second container. Add more water to the first container with the heavier particles in and repeat the pour. This process can be repeated multiple times to further refine the material. The resulting samples will range in particle size from sand, to silt, to pigment. The difference in particle size will often create a difference in colour, this is due to the relative masses of the minerals allowing for their separation. The finest sample may be the lightest shade as it contains finely ground alumina silicate material which is light in colour. 

4. Drying: 

Tools/equipment

Shallow trays

Dehydrator 

The refined, suspended particles are then poured in shallow trays and allowed to dry, either by natural evaporation or through artificial means in a kitchen dehydrator (dedicated to this role). The samples, upon drying, may clump back together, especially if they contain a lot of clay minerals that have adhesive properties.   

5. Grind: 

Tools

Pestle and mortar

The  purified, fine material can be used in various applications once ground once more in a pestle and mortar. Carefully pour or decant the material  into the pestle and mortar so that it contains a quarter of its volume, crush and grind the material into a fine powder. The time for this to happen varies but should take between 4-10 minutes. 

6. Sieve: 

Tools

Sieves in various mesh sizes (ranging from 40, 50, 60 to 100)

The number describing the fineness of the sieve alludes to the number of holes per inch

Using a fine geology test sieve (400 microns) sieve out any remaining lumps. These lumps can be re-ground or disposed of, or better yet retired to the earth in a garden or outside space. Most commercial pigments are 60 mesh or above. 

Method 2: 

After washing the samples is completed, pour off all the remaining water and leave the remainder to dry. As the pigment dries the finer pigment will come away from the bottom, heavier pigment in a distinct layer, this can be carefully separated by hand. This works especially well if the coarser level is partially sandy and the finer top layer contains finer, greasier clays, as they become very distinct. 

Applications of Levigation

1. Ceramics and Pottery: Levigation is used to refine clays, removing impurities such as grit or sand. This results in a finer, smoother clay that is easier to work with and produces a better quality ceramic or pottery product.

2. Pigments: In the production of natural pigments, levigation is used to separate fine pigment particles from coarser impurities. This is particularly important in the preparation of pigments like ochre, where a uniform texture and consistency are essential for use in paints and dyes.

3. Cosmetics: Certain earths, like kaolin clay, are levigated to produce a fine, smooth powder that is used in cosmetics, such as face powders and masks.

Historical references for the process of levigation and its use in ancient practices:

Theophrastus (4th Century BCE):

Theophrastus, a Greek philosopher and naturalist, wrote extensively on natural materials in his work On Stones. He described the extraction and processing of minerals, including the use of water to separate fine particles from coarse impurities, a method akin to levigation. His observations provide one of the earliest recorded accounts of mineral processing in the ancient world.

2. Pliny the Elder (1st Century CE):

Pliny the Elder's Natural History contains detailed descriptions of ancient methods for refining clays and pigments. He described how the Romans used levigation to purify clay for pottery and pigments for art, separating finer particles by mixing the material with water and allowing heavier particles to settle.

3. Dioscorides (1st Century CE):  

In his influential work De Materia Medica, the Greek physician Dioscorides mentions the use of levigation in preparing medicinal powders and cosmetics. The method of refining minerals and clays through suspension in water and decantation was common in the production of fine powders for medical and cosmetic purposes.

4. Agricola (16th Century CE):

The German scholar Georgius Agricola, often referred to as the father of mineralogy, described the levigation process in his work De Re Metallica (1556). Agricola outlined the refining of ores and pigments by suspending them in water to separate impurities, a technique that had been in use for centuries. His writings detail various methods for processing minerals and earths in the mining industry.

5. Cennino Cennini (15th Century CE):

In Il Libro dell'Arte, Cennino Cennini, an Italian painter, provides a practical manual for artists, including the preparation of pigments through levigation. He describes the method of suspending earth pigments in water, allowing the heavier particles to settle, and then decanting the finer pigments for use in painting.