In ancient Europe, before the introduction of oil paintings, fresco painting was a popular form of religious painting. Many works of art throughout Europe, centuries ago, use this method and form an important part of the cultural heritage. Michelangelo’s famous Sistine Chapel and Fra Angelo’s Annunciation in Italy are perhaps the two most famous examples of frescoes. But how exactly does the fresco process work?
The image is painted on a wall of wet lime plaster with the natural colors of the stone. Cement, made of calcium hydroxide, combines with water vapor and carbon dioxide in the atmosphere to form calcium carbonate. It gradually forms a protective layer over the pigments, preserving the image. In addition, it increases the mechanical strength of cement. However, this process takes decades, making frescoes a rare art form.
In this case, a group of researchers from the Department of Life Science and Applied Chemistry at the Nagoya Institute of Technology in Japan, including Professor Shinobu Hashimoto, Mr. Keitaro Yamaguchi, and Prof. Yuji Iwamoto, quickly made frescoes with cold ceramic sintering. a technique that was “geomimetic”, or inspired by the natural rock formations that occur in the upper part of the Earth.
The group’s work was made available online on the 4thth November 2021 and published in Volume 48, Issue 4 of Ceramics International at 15th February 2022.
Prof. Hashimoto explains the concept behind geomimetic ceramics. “This hardening method is so called because it mimics the structure of sedimentary rocks in the surface. It uses a heating device to heat calcium hydroxide powder up to 300 °C under high pressures of several hundred megapascals. These conditions harden the powder, creating the basic materials for frescoes. ”
The researchers painted on the bases made using red iron oxide pigment powder due to its low environmental impact. After that, they did the most powerful carbon dioxide treatment. Supercritical carbon dioxide is a form of liquid carbon dioxide that occurs when heated and held at very high temperatures and pressures. The use of very strong carbon dioxide in their process helped to form calcium carbonate on the painted surface.
To ensure that the pigment remains immobile on the surface of the water, the researchers placed the image in a heated press before the carbon dioxide treatment. The resulting calcium hydroxide layer showed visible light transmission and poor pigment reactivity.
In addition, to ensure a clear and transparent coating, the researchers mixed pigment powder with calcium hydroxide for painting instead of covering the fresco. The heaviest iron particles in the mixture settled and settled on the base, while the calcium hydroxide remained on top and uniformly covered the surface, and it eventually results in a layer of calcium carbonate.
The researchers found that a 1:10 pigment-to-hydroxide ratio by weight was sufficient to block the pigment particles. Adding hydroxide makes the paint white. They analyzed the structural characteristics of the produced frescoes using an electron microscope and energy dispersive x-ray spectroscopy to confirm the distribution of calcium and iron elements.
Finally, the researchers measured the difference in pigment color among different mixing ratios with a colorimeter. A mixture ratio of 1:10 showed interesting color development. In fact, its color was brighter than the original pure pigment. The researchers suggest that the calcium hydroxide particles scatter the red iron oxide pigments, reducing their size. That, in turn, increased the transmitted light power.
The results highlighted in this work will lead to the rapid production of frescoes made with mixed colors of calcium hydroxide, thermal pressure and strong carbon dioxide treatment. This fresco technique can also be used for the production of colorful images on pottery, which can serve as a push towards a new, energy-efficient, non-thermal technology.
Prof. Hashimoto oversees much of the current work. “Using our technique of painting, a fresco, which is a historical painting that takes centuries to create, was successfully created in one day. This finding may facilitate the use of unfired pottery technology for low-power communities. It is important to take cultural fields into account as past technologies can also contribute to current developments. ”
The new technique will surely bring a breath of fresh air to the time-honored art of fresco painting!
About Nagoya Institute of Technology, Japan
Nagoya Institute of Technology (NITech) is a respected engineering institute located in Nagoya, Japan. Founded in 1949, the university aims to create a better society by providing world-class education and conducting high-quality research in various fields of science and technology. To this end, NITech provides a nurturing environment for students, teachers and academics to help them translate scientific skills into practical applications. Having recently established new departments and the “Creative Engineering Programme,” a 6-year combined undergraduate and graduate course, NITech is striving to grow as a university. With the mission of “conducting education and research with pride and integrity, in order to contribute to society,” NITech conducts a wide range of research from basic to applied science.
Website: https://www.nitech.ac.jp/eng/index.html
About Professor Shinobu Hashimoto of Nagoya Institute of Technology, Japan
Shinobu Hashimoto is Professor and Research Faculty in the Department of Life Sciences and Applied Chemistry at NITech. He received his bachelor’s, master’s, and doctorate degrees from the Department of Engineering at Nagoya Institute of Technology. Prof. Hashimoto has authored more than 140 publications with 1190 citations and an H-index of 17. His areas of expertise include exotic materials, composites, and their surface and structural engineering. Now Prof. Hashimoto and his team are working on mineralogy, understanding crystal structure, and developing advanced techniques for making ceramics.
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