The advancement of science, including an understanding of color formation and visual perception, experienced a major leap during a period that would come to be known as the Islamic Golden Age. This period coincided with the medieval era in Europe where scientific discussions were confined to limited locations. In contrast, in the Islamic land, which extended from Spain to the Far East through Persia, major advances in medicine, mathematics, astronomy, alchemy/chemistry, and physics were witnessed by scholars and philosophers.
(d. 872) also known as the Second Teacher after Aristotle, and philosopher Suhrawardi,
(d. 1191) as well as Ibn Rushd,
, (d. 1198) were among those who promoted the Aristotelian views, including those on the formation of colors. According to this model, combinations of brightness and darkness, in varying proportions, result in formation of various colors. While Aristotle’s approach to color theory was mainly philosophical, the corresponding developments by Islamic scholars were often more empirical. A good example of the empirical nature of investigations in this period is color mixing. Among important scholars, faithful to Aristotelian view, in some regards, is the scientist Ibn al-Haytham,
, also known as Alhazen (d. 1039). Using a spinning top, he theorized color mixing and ascertained the need for a minimum length of time to observer individual colors. Fakhr al-Din al-Razi,
, (d. 1209), explained the color mixing on a millstone as follows:If we draw on a millstone from the center to the edge many lines of different colors, close to each other, and if the mill stone rotates fast, then we see only one color, which is evenly mixed from all these colors [1, 2].
Nasir al-Din al-Tusi,
, (d. 1274), Qutb al-Din al-Shirazi,
, (d. 1311), and Kamal al-Din al-Farisi,
, (d. 1318) also examined this experiment and provided commentary.
, (d. 1037), better known as Avicenna, devoted an entire chapter to color in his Kitab al-Shifa and was among the first to brake away from the Aristotelian color ordering [5]. Ibn Sina identified three different paths in color space that lead from white to black and proposed a two-dimensional ordering. His works would become very influential both in the East and in the West. In the translation of his Kitab al-Shifa [Liber de Anima], it is stated:Moreover, if whiteness does not exist without light and blackness not in ways already discussed then whiteness and blackness cannot only be joined in one manner. A manifestation of this is the fact that white gradually passes to black by three paths. The first is via pale (light [yellow-green]) and its progression is pure: it will indeed be of pure progression, at first it progresses to pale (light [yellow-green]), from there to grey (yellow-green), and continuing in this manner until black is obtained, because thus proceeding to its limit it does not veer from gradually stretching towards blackness, until it becomes pure black. There is also another path proceeding [from whiteness] toward red (light red), and from there to red brown (red), thereafter to black. The third path is the one going to green (blue-green), from there to indigo, thereafter to blackness. And in these ways not all color diversity can exist, neither can they be the source of the diversity of [Aristotelian] median colors [5].
, (d. 1276) who had asked a question about the color theory proposed by Ibn Sina, wrote that when yellow and blue colors are seen together, a green color is produced [6]. Al-Tusi recognized five different paths between black and white and stated:Regarding the production of colors from black and white there are numerous paths, from which one gradually walks from white to black. The path through yellow belongs there: First by the mixing of dense and fire, both in small amount, the strawyellow is produced, then the lemon-yellow, then the saffron-yellow, then the orange-yellow, then the grenade-yellow, then in it the tendency towards black increases, according to the increase in the number of dense particles and the decrease of fire, until it becomes black. Another path goes through red. First, it becomes rosy, then like evening-red, then blood-colored, then purple, then violet, violet-colored. One path goes through green. It becomes pistachio-colored, then leek-colored, then verdigris-colored, then egg-plant green, then naphta-colored. One path goes through blue. It becomes sky-blue, then Turkish blue, then lazur blue, then indigo-blue, then like kohl. One path goes through turbidity/dirt. It becomes grey, then darkish/dirt-colored, then dark etc. This all occurs according to the differences of particles in transparency, opacity (density), light and darkness. Now and then one sees a color together with another, and a different color is produced, such as green from yellow and blue, verdigris from green and white. There are infinitely many of such arrangements, and some are often found in small particles of plants and animals. Anyone who observes them is surprised by their number [7].
Several Persian scientists can be credited for their work on description of a limited hue scale. Abu Rayhan al-Biruni,
, (d. 1048) wrote a book entitled the Kitab al-jamahir fi ma’rrifat al jawahir (the book of the multitude of knowledge of precious stones) and discussed the colors of gemstones. Al-Jawahari al-Nishaburi,
, (d. 1196), also wrote a series of works on minerals and gemstones. Al-Tusi and later Aboulghasem Abdollah Kashani,
, (d. 1300) used and expanded these texts and were the first to describe a hue scale [7]. Nishaburi, for instance, mentions that by mixing blue and yellow pigments in different proportions, colors are produced that change gradually from blue, via green, to yellow.
, for instance, redefined the role of the medium in color vision and argued that color is produced by dense objects that block the sight [8, 9]:vision does not see the transparent medium, but it sees the object on the far side of it.
Often it changes with the incident light, so the water lily appears grey in sun light but red in candle light.
We find further, that for dense objects with bright colors, purple, blue etc., when they are located in weak light and similar places, then the colors appear turbid. When they are in strong light, they become bright.
…This behavior indicates that the eye observes the colors of colored objects only according to the colors that fall on them.
When a colored body is illuminated and its color is observed, and if one slightly weakens the light, then one sees a different color, that tends to pale/achromatic. If one weakens further, then one observes yet another color, tending to darkness. It continues like this, until the light disappears. Many colors are observed in this way, that are ordered in a regular series based on the weakness from the first until the disappearance [12].
Having examined various aspects of color theory and color mixing during the Islamic period, it is not difficult to suggest that the early Western investigators of color, such as Grosseteste, Bacon, and even Newton, either directly or indirectly were influenced by the developments made by Islamic scholars more than what is currently assumed. Chapter III includes a few Western scholars who examined color over the period of 13–15 centuries.