MINERALS YEILDING BROWN, BLACK, WHITES AND KHAKI COLORS
Mineral based pigments are classic example of sustainable alternatives for synthetic chemical dyes. In related post- Mineral (Earth) Based Pigments and Dyes– I, we discussed about minerals that yields Red, Blue, Green and Yellow colors. In this post we figure out the minerals that gives us earthy tones and neutral colors like Black, Whites, Brown and Khaki.
Minerals are inorganic compounds abundantly given to us by Mother Earth. They are rich sources of metallic ions, mineral salts and metal oxides and sometimes used for extraction of certain pigments to dye a yarn. Minerals are drawn out by mining and exploration techniques.
To obtain a mineral dye, the pigments present in a mineral are drawn out. The extracted the pigment is suspended in a medium and the medium bonds with the cloth. These mineral pigments works best with natural fabrics like cotton, linen, hemp, wool, and silk.
Earth pigments are known for their light-fastness (how resistant to fading it is when exposed to light) and fast drying.
BROWN AND ITS SHADES
1. BROWN OCHRE
The brown color covers a wide range of the visible spectrum and is a combination of yellow, orange, or red. Its shades are named as reddish brown, yellowish brown, dark brown, light brown and so on. As a mineral-based alternative, Brown ochre is a major source of obtaining brown pigment.
It is basically a limonitic rock which is a mixture of several minerals predominantly goethite. The pigment is absolutely stable and works best with Acrylics, Lime / Fresco, Ceramic, Oil, Tempera, Watercolor / Gouache, Cement.
Brown ochre is well documented in the ancient cave paintings which are still in excellent condition showing their color stability. It is compatible with all other pigments and is often used in mixture with other pigments.
For textile use the pigment is powdered to fine paste. Brown ochres can also be prepared artificially by a variety of procedures. The two main production methods:
- Precipitation of iron oxides
- Thermal decomposition of iron compounds.
Sienna is a yellowish- brown Earth pigment with oxides of iron and manganese. It was first mined near Tuscany and named as terra rossa (red earth), terra gialla, or terra di Siena.
Along with ochre and umber, it was one of the first pigments to be used by humans, and is found in many cave paintings.
Sienna is used in two of its popular forms:
- Raw Sienna– The naturally occurred sienna is yellow in color. This pigment is known as terra gialla.
- Burnt Sienna- The raw sienna when exposed to heat it turned out reddish brown and known as burnt sienna producing brown pigment. The pigment is also known as terra rossa. This pigment shows various color range including Burnt sienna pigment (Maerz and Paul), Dark sienna (ISCC-NBS), Sienna (X11 colour).
Since the Renaissance, it has been one of the brown pigments most widely used by artists. In the 20th century, pigments began to be produced using synthetic iron oxide rather than the natural earth.
Another mineral-alternative for brown dye is Umber. It is a natural brown or reddish-brown mineral which is darker than sienna and ochre. The name comes from terra d’ombra, or earth of Umbria, a mountainous region where the pigment was first extracted.
Likewise Sienna, raw umber is light in color but when exposed to heat, it turns darker and intense and thus called as burnt umber, suitable for both oil and water color paint.
Umber is not a word specific to one precise color, but it is a range of different colors, from medium to dark, from yellowish to reddish to grayish. The color of the natural earth depends upon the amount of iron oxide and manganese in the clay.
Seeking historical accounts, one can find ancient usage of Umber:
- Umber was one of the first pigments used by humans
- It is found along with carbon black, red and yellow ocher in cave paintings from the Neolithic period.
- The golden age of umber was the baroque period, where it often provided the dark shades in the chiaroscuro (light-dark) style of painting.
- It was an important part of the color palette of Caravaggio (1571–1610) and Rembrandt (1606–1669).
In the 20th century, natural umber pigments were gradually replaced by synthetic pigments made with iron oxide and manganese oxide. Natural umber pigments are still being made, with Cyprus as a prominent source.
BLACK AND ITS SHADES
Manganese Black is the pigment obtained from the silver-grey colored chemical element which is often found in minerals along with iron. The pigment shows stability in acids and alkalies and also at high temperatures. It shows excellent lightfastness, and is compatible with all other pigments.
Several colorful oxides of manganese used as pigments are :
- Manganese dioxide – Abundantly found in nature and have been used as pigments since the Stone Age. The cave paintings in Gargas that are 30,000 to 24,000 years old contain black manganese pigments.
- Pyrolusite – Often called as Mineral Brown Black is the most common manganese mineral. The pigment is dark brown or brownish black used as a coloring material in calico printing and dyeing. It imparts violet, amber, and black colors to glass, pottery, and bricks and used in the manufacture of green and violet paints.
- Manganese compounds have been used as pigments and for the coloring of ceramics and glass. The brown color of ceramic is sometimes the result of manganese compounds.
- It was used by Egyptian and Roman glassmakers, either to add to, or remove color from glass.
One of the common rock mineral and an important ore of iron. Magnetite yields excellent black color called as Roman Black Pigment. This natural black oxide is dense, opaque, non greasy, non toxic and imparts heavy permanent color.
India Black pigment is a Natural black Oxide from India which is suitable for all media including Artists Paints, Home Decor Paints, limewash, plaster, mortar and grout and more. The pigment has cool neutral tone and can be used with any medium.
IRON BUFF- NATURAL BLACK DYE
Iron buff is a fabric dye produced with the metal- IRON. In its simplest form, the clothes are dipped in iron springs, containing iron salts in solution. Dipping clothes in these springs and then exposing them to the air dyed them in iron rust color commonly called as ”iron buff”.
In fact, ancient greys and blacks were almost all dyed with iron together with plant tannins. Examples of this technique can be seen in the textiles of the Swiss Lake Dwellers (approximately 3000 BC). Egyptians also dyed with iron liquor and the sails of many Mediterranean fishing boats were dyed buff until quite recently.
Dyeing with iron produces buffs, dull yellows and oranges that are very fast to light and washing. To avoid shortening the life of the fibers too much, mostly cotton or linen are dyed using light shades. Fiber dyed with iron, has already been mordanted and could be over dyed to unusual shades with weld, madder and other natural dyes.
WHITE COLOR AND ITS SHADES
Many mineral yielding whites are used as a pigments for white colors, tinting colors and covering tones in paint as inorganic pigments are comparatively easy to disperse in most paint vehicles than organic pigments. They undergo treatment to improve their dispersibility, lightfastness and weather resistance.
ARAGONITE is a white to pale yellow mineral formed by biological and physical processes like precipitation from marine and freshwater environments, limestone caverns, near hot springs and geysers.
Aragonite is often found with gypsum, barite, malachite, calcite, quartz, clays, dolomite and limonite among many other minerals.
Historically, Aragonite was used along with dolomite and chalk for creating backgrounds and motives with other pigments by Romans. The long-lasting fluorescent properties of this pigment adds durability as well as luster and brilliance to color mixtures.
It is non-toxic and has good covering power as a white pigment in aqueous mediums, such as egg tempera, distemper and casein. However, aragonite is not effective in oil mediums, because of its low refractive index. It exhibits excellent fluorescent properties.
2. ZINC SULFIDE
Zinc sulfide is an inorganic compound which mainly occurs as zinc in the mineral ore sphalerite. In its raw form, the mineral is usually black due to the presence of various impurities but the pure pigment is white.
It is non toxic to humans and has good lightfastness but it is highly prone to weathering and therefore inadequate for outdoor paints. Ultraviolet radiation combined with humidity oxidizes zinc sulfide to the colorless zinc sulfate (ZnSO4) in paint.
Its uses as a pigment diminished during the past century due to its optical properties which are inferior to those of titanium dioxide. Zinc sulfide is used in paint that requires pigments with low abrasion qualities. This is perhaps its only advantage in comparison to titanium dioxide.
THE ULTIMATE – KHAKI COLOR
1. MINERAL KHAKI
Khaki is a color, a light shade of brown with a yellowish tinge. Mineral Khaki Color is produced by chemical reaction of metal salt – Iron and chrome more specifically (Iron buff and Chrome green color).
The color ranges from chrome yellow, chrome orange, chrome green to manganese brown, iron buff, khaki and Prussian blue.
Mineral Khaki Dye is :
- Generally used to dye cotton fabrics. It can not be used on silk or wool as it decreases the luster and flexibility of silk and wool.
- It is light fast.
- This color dyed is resistant to alkalis.
- It is used for army or military clothes.
Mineral khaki was abandoned prior to Ist World War due to large production of synthetic sulfur colors producing khaki.