The mirror as an object, and what it did to the face

Consider what it takes to see your own face. You need a surface that is flat to within a fraction of the wavelength of light, that reflects most of what strikes it without scattering, and that does not distort. Every one of those requirements was hard until very recently. For the great majority of human history, most people saw themselves clearly only in still water, if at all, and knew their own appearance mostly by report.

Stone and metal

The earliest surviving mirrors are made of obsidian, volcanic glass, ground and polished. Examples from Neolithic Anatolia are among the oldest known, and they are small, dark and slightly convex. What they return is not a portrait. It is a shadowy suggestion, a dark face on a dark ground, useful for placing an ornament and not much else.

Metal mirrors are the long standing solution, and they were made everywhere. Egyptian bronze mirrors are often circular discs on decorated handles, the disc echoing the sun. Chinese bronze mirrors were cast with elaborate reverse designs and are among the most sophisticated metalwork of the ancient world. Etruscan mirrors carry engraved mythological scenes on the back. Greek and Roman mirrors were bronze, sometimes silvered, occasionally hinged into a case.

All of them share two limitations. They tarnish, which means they need constant repolishing, and they reflect through the colour of the metal, which casts everything in warm brown or gold. A bronze mirror flatters. It is also permanently a little out of date, because the image degrades between one polishing and the next.

The glass problem

Glass mirrors existed in antiquity but were small and poor. The technical difficulty is not the reflective coating; it is making a sheet of glass flat and free of distortion. Medieval European mirrors were typically small and convex, made by blowing a glass sphere, coating the inside with metal and cutting out a section. Convexity is a way of avoiding the flatness problem rather than solving it, and it produces the fish eye reflection familiar from the mirror on the back wall of Van Eyck's Arnolfini portrait, in the National Gallery in London, which is one of the most studied objects in European painting and is, physically, a piece of ordinary fifteenth century domestic technology.

The breakthrough came in Venice. Glassmakers on Murano developed a method of producing flat glass of sufficient quality and backing it with an amalgam of tin and mercury, giving a bright, neutral, accurate reflection. The result was among the most expensive manufactured objects in Europe. Venetian mirrors were diplomatic gifts. The Republic guarded the technique with legal ferocity, and the eventual French success in establishing a competing industry, with royal backing under Colbert in the 1660s, was a state project rather than a commercial one.

The mercury amalgam process was also lethal to the workers who applied it. Mercury poisoning among mirror silverers is documented in the occupational medicine literature of the eighteenth and nineteenth centuries, and it is one of several places in this magazine where the manufacture of a beautiful object turns out to be the dangerous part.

Liebig, and the end of the luxury

In 1835 the chemist Justus von Liebig published a method of depositing metallic silver on glass by chemically reducing a silver solution. It is cleaner, safer, brighter and vastly cheaper than amalgam, and it is essentially the process still used. Within a few decades the mirror stopped being a possession and became a fitting. Mirrors went into hallways, over mantelpieces, into wardrobes, into public houses, into shops, into the interior of the modern city.

For four thousand years a clear reflection was a luxury good. It has been a household surface for about six generations.

The argument about self consciousness

Here we reach the interesting and contested part. A line of scholarship, of which Sabine Melchior Bonnet's history of the mirror is the best known example, argues that the arrival of the accurate mirror changed the experience of selfhood: that seeing your own face clearly, repeatedly and privately encouraged a new kind of interior self regard, and that this is connected to the rise of the self portrait, the autobiography and the modern idea of an individual with an inside.

The correlation is real and the timing is suggestive. Self portraiture as a serious genre develops in Europe in exactly the period when good mirrors become available to artists. Painters' self portraits often show the sitter's gaze fixed at a slight angle, which is what happens when you are looking at yourself in a mirror rather than at a viewer.

But correlation is where the evidence stops. The same period produced a great many other changes: printing, Protestant emphasis on individual conscience, urbanisation, the growth of a merchant class with money for portraits. Attributing interiority to a piece of coated glass is a strong claim resting on circumstantial support, and it should be read as a hypothesis that organises a lot of material usefully rather than as a demonstrated cause.

What the mirror meant

Alongside the object runs a symbolic tradition that is much older and considerably more interesting than the technology. In European art the mirror is at least three things at once. Held by a personification of Vanity it condemns. Held by Prudence it means self knowledge, because the prudent person sees themselves as they are. Held by Truth it means the world without flattery. The same object carries the opposite meaning depending on who is holding it, which is a rare thing in iconography and suggests genuine cultural ambivalence rather than a settled position.

That ambivalence has never resolved. The mirror is still the standard visual shorthand for narcissism, and it is still the standard visual shorthand for clear eyed self assessment. Every camera that has replaced it, from the daguerreotype through the film close up to the phone screen, has inherited both meanings intact, which is the subject of the essay on photography and, several technologies later, the front facing camera.

A last technical note

Modern domestic mirrors are second surface mirrors: the reflective layer sits behind the glass, so light passes through the glass twice. That produces a faint double image and a very slight green cast, because ordinary soda lime glass absorbs a little at the red end. Front surface mirrors, used in optical instruments, do not have this problem but scratch easily.

Which means that the face you see in a bathroom mirror is, very slightly, greener and softer than the face other people see. Not enough to matter. Just enough to be true, and to make the point that there has never been a neutral technology for looking at yourself.

Where to look

Readers who want to go further should start with the holdings themselves rather than with summaries of them. The British Museum, collection and the Victoria and Albert Museum both publish catalogue and research material relevant to this article. Both links are given for reference only. Neither institution has been assessed by us, neither has any connection to this magazine, and nothing here is an endorsement of any organisation.