The History of the Magic Mirrors of China and Japan

Among optical phenomena, none has captivated the scientific world as the so-called magic mirror, which produces light patterns like an act of magic.

Many are the historical variations on the origin of these magic mirrors. Consensus says that they appeared for the first time in China around the 2nd Century BC, and occurred in large quantities during the entire period of the Han dynasty (206 BC-24 AC). What we do know is that their “magical” quality was a completely accidental effect and just shy of wonderful. Few have seen one or even heard of one largely because in the West there are very few models left and because, after centuries of trying to understand their mechanism, science was able to reproduce it… And as we know, when a mystery is deciphered, infatuation is the first to suffer.

Magic mirrors, literally “light transmission mirrors,” are made of cast bronze and are generally circular, about 15 to 20 centimeters in diameter, with a polished surface, or front side, that produces quite a faithful reflection of the objects in front of them. On the reverse surface there is a modeled drawing in low relief that can be a landscape with trees, water, birds or animals, an inscription or perhaps a figure of Buddha. The “magical” quality for which they are famous consists of the fact that when strong light, such as a sunbeam, hits the front side and is reflected on a white wall, the image modeled on the back of the mirror appears as a pattern of white lines on the wall. Thus, of the luminous or speculative effects that we know of the world, this is certainly one of the most unexpected… of the most captivating.

The Chinese models, however, are extremely rare. So rare, in fact, that there is not one to be found in Paris, the city which, upon their discovery, was more than enchanted by them. But the Japanese also have their magic mirrors which, although slightly different in their manufacturing, produce the same spectrums of light, and their designs are certainly the most beautiful. Of these there are many around the world, probably because in ancient Japan mirrors were especially adored as rare and mysterious items, considered as a “source of honesty” because they reflect “everything that’s good and bad, the true and the false…without failure.” In fact, one of the most important imperial treasures of Japan is the sacred mirror called Yata-no-Kagami.

The first magical mirror that appeared in Europe was property of the Director of the Paris Observatory. Upon his return from China, he brought with him several mirrors, one of which was magical. This last one was presented as an irresistible mystery to the French Academy of Sciences in 1844––Nobody had seen anything similar, and despite their attempts to register its behavior, they could never fully understand it. In total, there are only four reported magical mirrors to be brought from China to Europe, but in 1878, two engineering professors presented the Royal Society of London with various models they had brought from Japan. The English called them “diaphanous mirrors” and for the first time they made technical observations regarding their construction. There effects were so wonderful that they hypnotized the Royal Society —which is to say a lot. Nobody, however, could ascertain what produced the ghostly and beautiful projection of light. While the metal on the front face is completely solid, the image reflected gives the impression that it should be transparent in some way. For many centuries the “magic” of these mirrors left scientists and collectors perplexed, who catalogued the phenomenon as an “impossible optical illusion” and therefore “magical.”

According to UNESCO, around 1,200 years ago, the secret was revealed in a Chinese text called Record of the ancient mirrors. But this book was lost a few centuries later. However, in 1932, scientist Sir William Bragg finally discovered why the reflection of the magic mirrors shows the design of its opposite side, and deduced that in its first appearances, the effect was a product of the accidents of the blacksmith’s trade, which consisted of rivets and hammer blows, among other things. As for the effect, he explained:

Although the surface of the mirrors is polished and seems completely flat, it has subtle convex and concave curves caused by the designed. Convex curves (outwards) scatter light and darken their areas of reflection. For their part, concave curves focus light and illuminate their areas of reflection. Mirrors are made of forged bronze, and the thickest parts are cooled at a different speed than the thin ones. Since the metal contracts a little as it is cooled, the different ranges of cooling “stress” or slightly deform the metal. The thin areas are also more flexible than the thick parts, so the polishing process, which should smoothen the metal until uniformity is achieved, exaggerates the slight differences in thickness. While we cannot see the pattern on the surface of the mirror, photos very clearly delineate it, so when they are able to bounce off the mirror’s curves, the pattern emerges.

Today it is rumored that Yamamoto Akihisa is the last manufacturer of magic mirrors in Japan. The Kyoto Journal interviewed him and the artisan explained part of his technique, which he learned from his father, who also learned it from his father, and so on, over generations. Our generation is just starting to learn about this object, which is already part of the magic history of human belief — but one that summons, as it very rarely occurs, science, aesthetics and symbolic intrigue alike.