From Past to Present: Egyptian Blue

From Past to Present: Egyptian Blue The color blue, thought to symbolize the cosmos, creation and fertility as a result of its connections with the sky and the Nile, was very important to the ancient Egyptian civilization. However, in ancient times only earth colors, that is, those present in the upper layer of the earth, were used as pigments, so blue was difficult to obtain for Egyptian painters. As a result of the researches, it is thought that Egyptian blue was first used in 2600 BC. From that date on, the use of this pigment expanded steadily in the ancient world, making its way into Mesopotamia and the Roman Empire until it disappeared in the Dark Ages. Unfortunately, a known Egyptian formula for the pigment does not exist, but Vitruvius, a Roman writer of the 1st century BC, noted that the pigment’s content is natural, including sand, copper (from a mineral such as azurite or malachite), and natron (a naturally occurring mixture of sodium carbonate). He reported that it is a mixture of sodium compounds formed as Corn blue (chemical formula: Ca-CuSi4O10) was obtained by heating these materials to 800-900°C and adding lime, a calcium-containing substance likely found as an impurity in sand. Whether it was produced intentionally or accidentally, it was an astonishing success that Egyptian blue was able to be achieved. In addition to maintaining the temperature control necessary for a successful reaction, the precise addition of oxygen would have to be extremely difficult to achieve. The constancy of the pigment over time is another example of the competence of Egyptian chemists. For example, composition in Old Kingdom (c. 2600–2100 BC) artworks such as Mereruka’s mastaba (or tombs) is nearly identical to that found in a mummy coffin from the Greco-Roman period (ca. 330–AD 400). In addition to the successful use in the past, Egyptian pigment seems to continue its effect today. In an exciting development for chemists and artists, it was reported in 2009 that Egyptian blue showed an extraordinary luminosity in the near-infrared region. This property means that the pigment can be easily detected in a completely non destructive manner by illuminating ancient works of art with near-infrared radiation. The luminescence is so strong that even when no blue color is visible to the naked eye, a very small amount of Egyptian blue can be detected. The British Museum had successfully used this technique to provide the first evidence that the Elgin Marbles were once painted, finding pigment in several sculptures from the Parthenon. Art historians as well as chemists who use luminescence are now realizing that this material can have important uses. For example, infrared’s long luminescence lifetime and greater depth of penetration in human tissue compared to UV or visible photons increase the possibility of obtaining more detailed and high-resolution biomedical images using pigment as an imaging agent. Also, a costeffective substitute for the expensive lanthanide compounds typically used in security inks is Egyptian blue. Researchers at Lawrence Berkeley National Laboratory in California have found a special blue hue to increase the energy efficiency of buildings by keeping walls and roofs cool in hot regions and to increase the production of some types of solar cells through high infrared emissions. Although it is already known that photons absorbed by the material can be emitted in the near-infrared range, new research has shown that the effect could be 10 times stronger than previously thought, as the material can emit as many photons as it absorbs. By measuring the temperatures of surfaces coated with corn blue and related compounds when exposed to sunlight, Berkeley Lab researchers found that fluorescent blues can emit almost 100 percent of the photons as they absorb. The energy efficiency of the emission process is up to 70 percent (infrared photons carry less energy than visible photons). This discovery expands our understanding of colors that work well to cool roofs and facades in hot regions. Although white is the most traditional and efficient option for keeping a building cool by reflecting sunlight and reducing energy use for air conditioning, building owners often want non-white colors for aesthetic reasons. Their understanding of Egyptian blue expands the refreshing palette of color options. Theoretically, this could result in integrated PV applications such as blue-tinted solar windows and transparent cells designed to absorb the near-infrared region of the light spectrum. In addition to its cooling potential for buildings, the fluorescence of Egyptian blue could also be useful in solar power generation. Photovoltaic cells at the edges used in blue-tinted windows can convert fluorescent near-infrared energy into electricity. Compilated by: B. Serhat Cengiz Resources https://www.ancient-origins.net/ancient-technology/egyptian-blue-oldest-artificial-pigment-ever-produced-001745 https://www.webexhibits.org/pigments/indiv/overview/egyptblue.html https://www.chemistryworld.com/features/egyptian-blue-more-than-just-a-colour/9001.article https://heatisland.lbl.gov/news/article/egyptian-blue-energy-efficiency https://www.indiatoday.in/education-today/gk-current-affairs/story/egyptian-blue-artificial-pigment-solarenergy-1366508-2018-10-11 https://pv-magazine-usa.com/2018/10/11/scientists-give-solar-pv-a-paint-job/