An ancient metalwork tradition for ritual and for function

Mirrors are usually considered primarily as implements for personal grooming but, in Japan, mirrors were used for far more than reflecting one's image. Within Japanese culture, mirrors are one of the most potent symbols of power, revered as sacred objects representing the gods. Mirrors are also admired as artistic objects, as they have intricate pictorial designs on their backs.  The technology needed to cast metal mirrors was introduced to Japan from China around the Yayoi period (ca. 3rd century BCE–3rd century CE). During the Heian period (794–1185), the mirror was included as part of the elaborate toiletry sets used by aristocrats. Though the earliest mirrors were fashioned after Chinese mirrors, in time mirror makers began to depict Japanese style designs and motifs from the Japanese natural world. In ancient times, round mirrors typically had a knob in the center of the back, through which a cord would be strung. Later, as the hand mirror (a round mirror with a rectangular protruding handle) came into use, designs became more pictorial, covering the entire back. These mirrors with designs on the back became popular among commoners in the Edo period, and the motifs used in these designs became diversified.
When European-style glass mirrors became popular during the Meiji period (1868–1912), bronze mirrors gradually fell out of use. Metalsmiths specializing in mirror making also began to disappear rapidly from Japanese society. The production of bronze mirrors would likely have ended all together were it not for the continuing production of mirrors dedicated to shrines and temples. After a metal mirror is cast using an alloy of tin or copper (known as "white bronze" or "bronze," respectively), the surface is ground and polished flat before being finally plated with gold. It remains an important task of the mirror master today to re-polish mirrors, including sacred mirrors. In the past there were various types of artisans for each stage of mirror production, including polishing mirrors. Today, however, professional mirror metalsmiths must handle every aspect of mirror making themselves.
Creating a design
The designs on the back of mirrors tend to include motifs of things found in nature (plants, flowers, birds and butterflies), landscapes, or auspicious motifs like the crane. Intricate and detailed designs are avoided, as the basic shapes must be formed using sand. The loam molds that are used to cast mirrors are particularly suited to designs in high relief. 
Loam mold making
Sand (loam) is mixed with binder composition and additives to create a loam mold, based on technology used since ancient times. Three layers of loam (coarse, medium, fine) are placed over the frame to make the base mold. Shapes are patiently created by pressing in the sand with a tiny spatula-like tool. Care is taken to ensure that the sand mold does not collapse as the design is formed. It takes between one and two months to finish this process for a mirror with a diameter of about 5 cm, or two to four months for one that measures 20 cm in diameter. Once the design is fully created, the mold is then left to dry before being biscuit fired.
The mold is moved to the foundry for casting. The casting alloy (a mixture of copper and tin are used to make bronze) is melted and poured into the mold. 
The sand from the loam mold is removed completely from the casting mold the next day and the cast mirror is then brought back to the workshop.
The mirror comes out of the mold with unnecessary parts such as the sprue (the protrusion where the metal was poured into the mold) still attached. These parts, the edge, and the surface of the mirror are sanded down and polished. 
Next, oxide film is removed using a file, and the filing marks are removed with a knife-like tool called a sen. Any unevenness caused by the sen is polished down using a whetstone. 
A final step is to smooth and buff the mirror's surface with charcoal. The preferred charcoal for this task comes from the bigleaf magnolia or tung wood. In this way, the surface of the mirror is finished step by step to eliminate marks and unevenness. In the past there exited a process known as hontogi whereby the metalsmith would rub mercury onto the mirror. Today, the surface is rubbed instead with nickel or a nickel amalgam.
Makyō (magic mirrors)
Finally, let us take a look at some little known but amazing Japanese mirrors. When sunlight hits the mirror shown here, it reflects a hidden image onto the nearby wall. In Japan there exist mirrors that can reflect characters or pictures onto walls even though no such design is visibly evident on the mirror's reflecting surface. These are known as makyō (magic mirrors).
Makyō (magic mirrors)
A Japanese magic mirror does not reflect the relief design cast on the back. Nor does it have any obvious irregularities on its reflecting surface. So how does a magic mirror work? The secret image is actually cast into the design on the back of the mirror's reflecting surface. The secret image areas are made to be thicker than the rest of the mirror. Then, in polishing, the thickness of the reflecting surface is typically buffed down to about 1 mm in thickness, but it can be buffed more deeply in the secret image areas because the metal there is thicker. The resulting thinner, raised non-image areas deflect light differently than the lower, thicker image areas. These differences are not easily visible to the naked eye. Although it may seem that a magic mirror has been polished uniformly, there is actually minute unevenness invisible to the eye. When light is reflected off this subtly uneven surface onto a wall, the design will reflect differently from the rest of the mirror to reveal its secret image.
Makyō (Magic Mirrors)
Makyō mirrors were first produced during the Edo period (1615–1868). Although production ceased for a time, it was revived around 1974 by Yamamoto Ōryū, who was designated as a Living National Treasure (officially, a Holder of Important Intangible Cultural Property). In June 2014 Prime Minister Abe Shinzō made headlines  during his visit to Italy by presenting a magic mirror with hidden Christian imagery to Pope Francis. 
By: Art Research Center, Ritsumeikan University in collaboration with Kyoto Women's University
Credits: Story

Information provided by YAMAMOTO ALLOY WORKS CO., LTD.  

Supported by Kyoto Museum of Traditional Crafts, Fureaikan

Photo by Stria photographics

Text written by Yamamoto Masako(Research Fellow of Japan Society for the Promotion of Science (JSPS)), Art Research Center, Ritsumeikan University 

English Translation by Eddy Y. L. Chang

Edited by Melissa M. Rinne, Kyoto National Museum

Exhibition created by Shimizu Ayano, Kyoto Women's University, Lifestyle Design Laboratory

Directed by Maezaki Shinya, Kyoto Women's University


Credits: All media
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