NATURAL IRON OXIDE PIGMENTS -3 # Ochers

Post 408 –  by Gautam Shah 

.

12802736905_9f0847811c_z

Ochre is an iron oxide pigment of natural and synthetic sources. Ochers are coloured soft deposit of clays often with mixed layers or pockets harder crystalline iron ore. Some of the best yellow ocher’s are mined at Roussillon, Southern France. Here the mineral formations are naturally stained with colours to provide a wide variety of earth or natural iron oxide colours.

ocher_rocks_rock_ocher_roussillon_places France

The Greek word ochros, for Ochres describes it to a pallid or pale yellow, but natural ochers are brilliant colours. Ochres have a colour range that varies from yellow to deep orange or brown, due to the hydrated iron oxide. This is unlike the Red oxide which is from hematite powder, a form of iron oxide (Fe2O3). An ochre containing a large amount of hematite has a reddish tint, and is known as ‘red ochre’. The dominant yellow colour of ochre is due to the mineral limonite. Ochres are of two kinds, one with an argillaceous or clayey basis has richer colours, whereas the other with a calcareous base is slightly of ‘flatter’ colours. The nature of the associated minerals affects the colour, such as calcareous varieties have brownish-red and dark-brown shades, and aluminous types offer red and violet tints.

Vaucluse-roussillon-village

Earth colours of Roussillon village France

Different colours of Ochre pigments are extracted from different veins, and then mixed to obtain specific shades. Other shades are created by roasting (‘burnt’ or calcination), and dehydrating the mineral clays.

Santorini_girl_picks_flowers

Yellow Ochre is a very ancient pigment. It is without any trace of green. The oxide colours are called Earth colours, due to their richness, brightness and warmth. Ochres are mixed with high refractive whites like Lime (or zinc, titanium dioxide), or low refractive ‘extenders’ such as the barytes to achieve, respectively, high opacity or translucency.

800px-Manuscript_Cover_with_Krishna_Raising_Mt._Govardhan_(inside)_and_the_Coronation_of_Rama_(outside)_LACMA_M.88.34_(1_of_2)

Manuscript Cover India in Ocher colours

In Ancient Greece, red-ocher was called miltos, (hence Miltiades red-haired or ruddy). In Athens when assembly was called, everyone was supposed to attend it, and failure to attend it incurred a fine. To prevent people loitering around slaves swept the open space of the Agora with ropes dipped in miltos . It was also known as raddle, reddle or ruddle. In Ancient Egypt, the ochre was often used in place of gold, which was considered to be eternal and indestructible. It was used for painting tomb interiors in place of toxic orpiment (an orange-yellow coloured arsenic sulfide mineral). Ochre was used for painting women’s faces. Romans used the yellow ochre to to represent gold, skin tones, and as a background colour in their paintings such as the murals of Pompeii.

Egyptian Ocher colours

A rational process for refining ochre pigment was developed by the French scientist from Roussillon province of France, Jean-Étienne Astier (1780s). He washed the clay to separate the grains of sand from the particles of ochre. The decanted and dried ochre was crushed, sifted, and ground as the pigment. Best of the qualities were used for artists’ colours.

Three_saddhus_at_Kathmandu_Durbar_Square

Ochre robed Sadhus sitting on the Vishnu Temple of Kathmandu’s Durbar Square, Nepal Wikipedia Image by us Koljonen (Dilaudid)

Advertisements

NATURAL IRON OXIDE PIGMENTS – 2 # Red Oxides

Post 407 – by Gautam Shah 

.

The first primitive colours, ranged from yellow to brown to red to near black. These came from three basic materials that are Oxides of Iron, Calcium and Carbon, respectively for Red-brown, White and Black colours. The ‘earth colours come from inorganic minerals like, Iron oxides with its various stages of hydration, and Manganese oxides.

Iron Oxide Red

The chief earth colour constituent, Red hematite powder, a form of iron oxide (Fe2O3), was found scattered around the remains at a grave site in a Zhoukoudian cave complex near Beijing. The site has evidence of habitation as early as 700,000 (?) years ago. The hematite might have been used to symbolize blood in an offering to the dead. It was also used in powdery form, 164,000 years ago by the caveman of ‘Pinnacle-Point’ (caves in South Africa), possibly for body painting. Hematite residues are also found in old graveyards from 80,000 years ago. Hematite as a mineral, is coloured black to steel or silver-gray, brown to reddish brown, or red. The various forms hematite show variegated rust-red streaks or bands. The word Hematite is a Greek word haimai that alludes to red colour of the blood.

Iron bands

Hematite is harder than pure iron, but very brittle. In steel-gray crystals with metallic lustre, hematite is called specular iron ore whereas thin scaly ones are known as micaceous hematite. Most hematite occurs in a soft, fine-grained, earthy mineral form of red ochre or ruddle. Red ochre has been used for body coating and cave art painting. It is now used in paint pigment, for primers, and as a polishing medium or rouge for finishing plate and spectacle glasses.

lronoxide-red-718433

Venetian red

Rusted Iron colours

Limonite (hydrous ferric oxide) ranges from yellow to brown. These are known as Ochre, Sienna, and Umber. Ochre is clay-coloured with hydrated iron oxide. Tuscany, famous for its ‘Terra di Siena’, is a hydrated iron oxide with silicates and aluminates that endow some transparency to the pigment (Silicates and Aluminates are extenders, with a lower refractive index, so add to the bulk and increase the transparency). When limonite is heated for calcination, the water part is removed to form ‘Burnt Sienna’.

Oxide colour painted Barrackpore Railway Station North 24 Parganas W Bengal India > Wikipedia Image by Biswarup Ganguly

Venetian red is a slightly darker than a scarlet red, but less intense colourant from purer form of hematite. It was also called Sinopia due to its origin from Sinop in North Italy. Similar colourants (of pure hematite) were called Ocra rosso or red ochre. Due to its pure quality, the pigment, when mixed with white, produced a likeable pink. The red Sinopia or Sinoper and its lime mixed pinks were used in Italian Renaissance paintings for body tones. It formed the major ingredient in the colourant called Cinabrese. Sinopia was used for the cartoon or under-painting for a fresco.

Sinopia

Red oxide colours were not perfect red colours. These had either a yellow-brown tinge or blackish shade. The colour available in dyeing of fabrics gave that desired perfect red. Dyes were not preferred for paintings or wall art for two reasons, One, dyes were soluble in water and had lesser opacity (‘covering or hiding capacity’) Egyptians used the root of the Rubia, or madder plant, to make a dye, later known as alizarin. This was mixed with whites powders of low refractivity, and used as a pigment (known as madder lake, alizarin or alizarin crimson).

Ajanta Caves, India Oxide based earth colours

Ajanta Caves, India Oxide based earth colours

The earth colours have been extensively used in Ajanta and wall arts at several places. The early works show range of earth colours mixed with white and only occasionally greens. The mixing of ochre (in absence of pure yellows) produced darker or olive green effect. Pure pinks were absent.

Buddhist Monks on pilgrimage varied shades of earth colours Wikipedia Image Credit: Tevaprapas Makklay

In India the Earth colours have also been known as Bhagawa and Gerua. Bhagawa is brownish or more towards Ochre, whereas the Gerua is a red iron oxide colour. Both the colours show regional variations. Bhagawa colour has been colour of attire for Hindu and Buddhist monks. Geru or Gerua colour is used on water and plant pots and buildings. It is used as a decorative coating with lime white, on lower sections of tree trunks. Temples in South India have Gerua coloured stripes on external face. Buddha adopted the colour for own robes, because at that point of time it was the colour of prisoners’ dress. Sikhs adopted the Bhagawa colour, but now their choice leans more on purer synthetic orange or saffron, than earthy colour Bhagawa.

Varanasi (Benaras) India Gerua coloured Durga temple Image by Henk Kosters https://www.flickr.com/photos/68556734@N00/741206048

For translators, transliteration of colour, is always problematic. Colour names are closely linked to their cultural interpretations. So, for the Indian classical story of Nala and Damayanti, “the king loses the kingdom in gambling, and retires to forest. His wife queen Damayanti renunciates the world to accept the asceticism. She starts wearing Bhagawa or earth-brown coloured clothes”. A Russian translator perceives the mood, but reinterprets for his own culture and makes Damayanti wear Black, the colour of widowhood. Today, Western reporters claim the Gerua or Bhagawa to be colour of Saffron, and link it to Hinduism.

Typical Iron Oxide Red Shades

  •     Hex: #6E0303
  •     RGB: 110, 3, 3
  •     CMYK: 0, 0.973, 0.973, 0.569
  •     HSV: 0, 97, 43

france-1882847_1280

 .