[Pigments and Binders]

Alizarin

Alizarin, is the main colorant found in the madder plant Rubia tinctorum. (Fitzhugh,119) Alizarin red is also known as Rubia, Rezza, alizarin crimson, crimson madder, and rose madder. (Fitzhugh,119) Its pigment code is P.Red 83 and its color index number is 75330. (Rossol, 115) Alizarin is a unique pigment in that it is a lake. This term is a bit confusing for those unfamiliar with painting terminology. A lake is a pigment made by precipitation of a soluble dye with a metallic salt or acid complex with a base. (McLaren, 2 & Bomford) Common alternatives that are similar to alizarin lake are munjeet and Nakai. (Fitzhugh, 116)

History of Use by Artists

Alizarin was used for dying cloth in Asia in ancient times. Also, it was found in excavations at Pompeii, and in Egyptian textiles from as early as 1567 BC, and in Corinth from 146 BC. Later, in the Middle Ages, Charlemagne himself promoted the cultivation of madder. However, alizarin and madder were not used on paper until much later in 972 AD, where it was used as ink in the marriage certificate of Empress Theophanu. (Fitzhugh, 111)

 

Later, alizarin began to be used for painting. Alizarin was found painted in a book illustration from a book of 1465-1489 in the Advocates Library in Edinburgh. (Fitzhugh, 111) After the Middle Ages, in the 17th and 18th centuries, alizarin was used for paintings. In the late 1800s, it was used for colorant in ceiling waxes. Then in 1891, the first alizarin was used in watercolor by artists such as J.M.W. Turner.
(Shown above: alizarin combined with the binder egg tempera. Used for painting.)

Generally, in painting, alizarin has been used as a glazing lake. It is a fairly permanent pigment which mixes well with water, alcoholic solvents, and oil. On a lightfastedness scale of 1-8, alizarin ranks seven because of its tendency to fade very slowly. (Fitzhugh, 114)

Recently, Alizarin has been synthesized. Chemical studies on alizarin lead to its synthesis in about 1870. Now, because of its easy synthesis, artists mainly use alizarin in its synthetic form. (Fitzhugh, 119)

 

Source/Preparation of Pigment

Alizarin is one of the two main dyes, the other being purpurin, that come from the root of the madder plant. Alizarin tends to be reddish while purpurin tends to be more pinkish. Artists extract alizarin dye to make a red lake pigment which they can use in paints. (Bomford et al, 33).

The steps in the commercial preparation of alizarin lake are fairly complex. First the madder is uprooted from the ground and left to dry in fields in small piles. After that, it is put in larger piles for 2-3 days and then it is dried in warm air drying houses. Next, the dried roots are crushed and separated from the bark by sifting. Finally, the roots are crushed with stones and sifted to a fine powder. (Fitzhugh, 117)

Some madder cannot be used immediately for dyeing; Alsatian and Dutch madder must remain in barrels for one or two years where it ferments. Avignon madder has significantly better quality if it is stored, but it can be used immediately. (Fitzhugh ,118) Not only was madder stored for years to improve quality, but it was also generally harvested three years after planting to increase its dye yield. (Fitzhugh, 115)

In class, we used synthetic alizarin to make a variety of paints. This synthetic alizarin created good consistency paints and had a beautiful hue. The creation of synthetic alizarin probably helps to reduce the likelihood of contamination of alizarin, which can result from organic and inorganic substances. Inorganic contaminates include brick powder, ocher, yellow clay, yellow sand; organic contaminates include oak shavings, logwood, redwood, sandalwood, and almond shells. By synthetically creating alizarin, it is easier to control what it comes in contact with. Alizarin found in nature could have any one of the contaminates. (Fitzhugh, 109-135).

Chemistry of the Pigment

Madder is found as a glycoside in the roots of the Rubia tinctorum. Fermentation of this root yields alizarin. (McLaren, 5) When the dead roots ferment, the glycosides hydrolyze and yield free anthraquinones. This process causes the powder particles to stick together and form a solid mass (a lake). (Fitzhugh, 118)

Alizarin can be combined with varying strengths of alkali or acids to create different hues of red. A strong alkali will create a violet-blue color, while a strong acid will create a yellowish red. The color of the lakes is also influenced by the metallic salts used: the alumina lake is rose red or bluish red with calcium, the tin lake is red-violet, the iron lake is black-violet, and the chrome lake is brown-violet or red-brown. (Fitzhugh, 119)


Unlike other lakes, alizarin does not bleed red when boiled with sodium carbonate solution. Also, it does not dissolve when boiled with ammonia. This allows alizarin to be easily separated from other substances like carmine. (Fitzhugh, 115)

Binders

To make paint with a lake, the artist must combine it with a liquid binder. Alizarin lakes are compatible with a variety of paints and sufaces, including oil, watercolor, tempera, dry interior plaster, and chalk. (Fitzhugh, 115) In our experiment, we prepared oil, watercolor and tempera paints and applied them to watercolor paper in various combinations with other pigments. Alizarin created a beautiful color that combined well with the other pigments in all forms. The oil paint was very smooth but absorbed a great deal of linseed oil (1.054 grams of alizarin absorbed 75 drops of linseed oil) to get a smooth consistency. This is not surprising, since madder lakes have an oil absorption rate of 70% oil and dry poorly. To increase the drying process, artists add varnish. (Fitzhugh, 115) Our watercolor (gum arabic solution: 19 drops combined with 1.07 grams of alizarin) seemed a bit grainy but, when water was added, the graininess disappeared and it brushed on smoothly. The egg tempera (about 35 drops of egg yolk combined with 2.189 grams of alizarin) was the only paint that remained grainy during application. This was perhaps because not enough egg was added to create a smooth consistency.

Traditionally, alizarin is used for glaze because of its translucent tendency. The best lake glazes come when alizarin is mixed with oil, an idea originated by the Italians. However, most red lake pigments tend to fade when exposed to light for long periods of time. The artist can eliminate some of this fading by using the alizarin in a pigment mixture instead of just using it as a glaze. Some substrates that the pigment can be mixed with include hydrated alumina, eggshells, marble dust, and chalk. (Bomford et al, 33).

 

 

Optical characteristics: Including looking through the microscope

The color of natural madder lakes depends on the two things: the organic colorant and the inorganic substrate that it precipitates with. (Fitzhugh, 112) Lakes made with alizarin usually produce some shade of red, but the precipitating substrate makes a big difference. For example, tin makes the madder lake more intense, iron sulfate makes black violet, and chromium alum gives the lake a brown red color. For the best red, iron free alum works best. (Fitzhugh, 112)

Natural alizarin varies from scarlet to pink to red with a bluish tint. (Bomford et al, 33) However, our synthetic alizarin was a deep red with little variation. When viewed through a microscope, this alizarin showed a wide variety of shapes and sizes of particles. Usually, these particles were irregularly shaped, and ranged in size from about 0.2 microns to 38 microns. While these particles were always red in color, they had a wide range of color concentration and darkness. The pools of alizarin ranged from opaque to translucent. Since alizarin could not be seen through polarized light, we determined that it was not crystalline.

(Shown here: Alizarin itself.)

 

Health Issues

While alizarin is not highly toxic, it shouldn't be handled for long periods of time, eaten, or rubbed in eyes. It has been found to be related to cancer causing anthraquinones. (Rossol, 115)

Links to other Web sites

To view an alizarin time line, click here.

If you are interested in purchasing alizarin for painting, etc., click here.

To view a web page on madder, click here.

Amber Hodges, Freeman Rogers, 1998.