Mirrors are one of the most versatile decor items around. Whether they’re used to make a room feel bigger or serve as a centrepiece, they can have a huge impact on the overall look of a space.

To be a mirror, a flat surface must reflect light waves without diffusing or transmitting them. This is what distinguishes it from a normal glass surface.

The natural world offers many mirrors, from the surface of water to the polished surfaces of stone and metals. But mirrors made of glass have become the most popular for use in human society. People have been using them since prehistoric times—for decoration, for divination, or as status symbols. In fact, in the 1940s, researchers discovered seven concave mirrors in a Mayan tomb, which archaeologists believe were hung to reflect light and allow the dead to see their reflections. Today, we use mirrors for a variety of reasons, including to make objects in our homes appear bigger and brighter or for safety, security, and visibility.

Throughout history, the production and manufacture of mirrors has improved along with advances in science and technology. The first glass mirrors, for example, were so delicate that they could easily break. The ancients tried to remedy this by coating their glass with metal, but such mirrors were expensive and difficult to use.

It wasn’t until the 16th century that a technique for coating glass with mercury gave rise to a new generation of mirrors. Venetian glassmakers kept their secrets so tightly guarded that they locked away skilled craftsmen on the island of Murano and forced them to work under sweltering conditions tending volatile furnaces and exposing themselves to mercury, which was not yet recognized as dangerous. But some spies managed to bring the secret back to France, and soon a whole new generation of mirror makers was making glass from Venice.

As mirrors became more available and affordable, their popularity grew as a tool for personal grooming and social interaction. They also served a more esoteric purpose: Some cultures believed that gazing into a mirror could be a portal to another dimension, allowing them to see the ghosts and spirits that inhabited the otherworld.

As more advanced technology enabled mirrors to be made more cheaply and with greater accuracy, they began to be used in a wide range of applications, including art and architecture. For instance, one-way mirrors allow windows to be positioned in buildings so that they can deflect sunlight and heat while still letting in light—saving energy and money in the process.

Materials

A mirror is an optical device used to reflect light and, as such, it must be made from a material that will allow the majority of light to pass through. The most common substrate for everyday mirrors is glass, which is chosen because it is affordable, rigid and easily shaped. It also has the property of being highly polished and therefore able to take an excellent reflective coating.

There are a variety of metals that can be used to coat the surface of a mirror, depending on the intended use. Silver and aluminum are the most commonly utilized metals for this purpose. Other coatings are available as well, such as silicon oxides and silicon nitrides. These coatings, which are sometimes referred to as dielectric coatings, can be applied over metallic coatings for additional protection and enhanced reflection for specific wavelengths of light.

When designing a mirror, it is important to consider its location within the overall interior space. If it is not carefully positioned, it can draw the eye and compete with other elements for attention, distracting from the overall look of the room. This is especially true of decorative items that compete with the reflections of a mirror, such as a piece of art or an antique.

Fortunately, newer and more advanced technologies have been used to make mirrors easier to produce in large quantities at a reasonable cost. This has led to a great proliferation in their use as a design element.

A quality mirror is a design accessory that can enhance the appearance of any interior space. Properly placed, it can amplify natural light and highlight any decorative features or objects. This effect is maximized when the glistening surfaces are contrasted against any unfinished or rough natural textures found in the room. Mirrors also offer a sense of openness by reflecting light and providing a glimpse into the distance. This is especially useful in rooms that are small or lack ample windows to allow sunlight into the home. In addition to enhancing the aesthetic of a room, a mirror can be used to show off an item, such as clothing or a piece of jewelry, that may otherwise be hidden from view.

Techniques

Mirrors must reflect as much of the light that hits them as possible. They should also transmit and absorb as little as possible. Surfaces that diffuse or scatter light (as opposed to reflecting it) will cause distortion, blurring, and loss of line quality, contrast, and color. Flatness is another important attribute; mirrors that are not completely flat can distort or magnify objects in the environment.

Metals have long been used to produce mirrors, and the process is called silvering or golding. To create a mirror with this technique, a piece of glass is prepared and then coated with a layer of the metal. The glass must be perfectly clean and smooth to ensure that the reflective coating adheres properly. A thin layer of aluminum is most commonly used in modern mirrors. This is applied using a multi-layer automatic coater, with the first surface of the glass (called the front surface) being coated with this material.

Once the metal layer has been applied, a protective or dielectric layer may be added to prevent oxidation and scratching. Dielectric layers are typically made from gases, like silicon oxides or nitrides. These can be added in a variety of ways, including chemical reactions and plasma deposition.

Aside from the materials used, other factors that affect mirrors include their surface quality and finish. A high-quality mirror is characterized by a clear, uniform surface that has been polished to remove blemishes and imperfections, which will make the reflection more accurate. The mirror must also have a consistent thickness across its surface to avoid a distorted image.

Mirrors can be made to reflect only certain wavelengths of light, while passing through others. This type of mirror is known as a beamsplitter, and it is often used to separate light into different colors for various applications. Mirrors that can be patterned by applying metal stencils to the surface are also available, and this can add design elements or enhance performance characteristics of a mirror.

Newer, cheaper techniques for producing mirrors in the 19th century led to widespread adoption of these devices in households and public spaces. This was largely driven by the increased popularity of mirrors as grooming aids, encouraged by publications on household decor and social etiquette that were endorsed by the bourgeoisie.

Manufacturing

Mirrors are coated with metals that reflect a specific range of light frequencies. Aluminum and silver are two of the most popular metals used to coat mirrors because of their high reflectivities, durability, and affordability. Before a mirror can be coated, it must first be polished to achieve an optically flat surface. Any dips or imperfections on a mirror will cause distortion of the image it reflects and thus, must be eliminated. The process of polishing is very energy intensive as it requires a great deal of heat that is derived from fossil fuels.

The next step is coating the mirror with the desired metal. This is done by bringing the metal to a boil in special chambers and then applying it to the glass sheet. Once again, this process is very energy intensive as it also requires a great deal of heat to maintain furnace temperatures and vaporize water. After the mirror has been coated in its desired metal, another layer of copper is applied for durability. The final step is the addition of paint.

Once a mirror has been finished, it is shipped to its new home where it will be used for many years until it either breaks or the owner decides to switch it out with something else. This entire process is very wasteful from an energy perspective because all of the materials and the energy put into making a mirror ends up being wasted when it is thrown away.

In the past, mirrors were made by coating a piece of glass with mercury but this process was eventually abandoned due to its toxicity. In the 16th century Venice became known as a center for mirror production with their technique of using a silver-mercury amalgam. However, this process was expensive and the mirrors were a luxury that only the rich could afford to own.

Modern mirrors are mainly made by wet deposition of silver or aluminum. This means the glass is cleaned and sputtered with liquid silver or aluminum which is then allowed to dry. To prevent oxidation and scratching, a dielectric coating is often added to the metallic mirrors. Scientific mirrors are sometimes coated with other metals or even gold to enhance their reflection for particular wavelengths of light.