Smart glass: what it is and how it works

What smart glass is

Smart glass is a special type of glass that can switch from transparent to opaque with a simple electrical command. In an instant, the same surface stops being a window you can see straight through and becomes a translucent white wall that protects privacy, then turns clear again whenever you need it. Because of this ability to change state, it is also known as switchable glass: its optical behaviour is not fixed, but adapts to the needs of the moment.

The difference compared with ordinary glass is fundamental. Conventional glass is always the same: either clear, or frosted, or permanently darkened. Smart glass, on the other hand, combines two opposite functions in a single element. When it is switched on it lets light and sightlines pass through like normal glass; when it is switched off it turns milky and conceals whatever lies behind it, with no curtains, panels or extra fittings. It is privacy on demand, but much more besides, because that same opaque surface can turn into a screen.

It is precisely this dual nature that makes smart glass so appealing to those who design spaces and to anyone looking for interactive communication tools: a partition that protects confidentiality can, when required, become a surface onto which images, video and content are projected. A single pane plays the role of glazing, privacy screen and projection surface all at once.

How it works: PDLC technology

The most widely used technology in smart glass is known as PDLC, short for Polymer Dispersed Liquid Crystal, a layer of liquid crystals dispersed in a polymer. It is worth understanding how it works, because it neatly explains both the behaviour of smart glass and its practical limits.

Liquid crystals that line up

Inside a sheet of PDLC glass there is an extremely thin layer containing tiny droplets of liquid crystals suspended in a transparent plastic material. When the glass is not powered, these crystals are arranged randomly and in disarray: incoming light is scattered in every direction and the surface appears white and opaque, exactly like frosted glass. This is the resting state, the one that guarantees privacy.

When an electrical voltage is applied, on the other hand, the liquid crystals all line up in the same direction. At this point light passes through the layer without being scattered and the glass turns transparent. As soon as the power is removed, the crystals return to their natural disorder and the surface becomes opaque again.

Almost instant switching

The transition between the two states is practically immediate: it takes only fractions of a second to see the glass clear or fog over. This translates into simple, instant control via a switch, a remote, a sensor or a building automation system. It is worth bearing in mind one detail that shapes design decisions: in the most common configuration the glass is transparent when powered and opaque when switched off. This means that in the event of a power cut, the surface naturally reverts to protecting privacy.

The active liquid-crystal layer can be sealed between two sheets of glass to create a complete switchable pane, or it can be produced as a film to be applied later to glass that is already installed. We look more closely at this second option further on, as it is particularly useful for anyone who would rather not replace their existing fittings.

Smart glass as a projection screen

The most interesting feature for communication is that, when smart glass is in its opaque state, it makes an excellent surface to project onto. The very quality that makes it milky and able to hide what lies behind it, namely the scattering of light, is also what allows it to capture and display a projected image.

In practice, this type of projection glass lends itself very well to rear projection: the projector is positioned behind the glass, on the side hidden from the audience, and the image appears crisp on the surface facing the viewers. The result is a screen that seems to float in mid-air, with no frame and no conventional projection screen, elegantly integrated into the architecture of the space.

One point is important to be clear about: smart glass does not generate images on its own. You always need a source, namely a dedicated projector, and in many cases a system to manage the content as well. The glass provides the ideal surface, but the light comes from elsewhere. For the same reason, the best results are achieved in spaces with controlled lighting or in the evening: like any projection, this one performs at its best when ambient light is not too strong and does not wash out the image.

This combination opens up concrete possibilities. A shop window that shows what is inside the store during the day and turns opaque in the evening to host a projected promotional video. A meeting-room partition that becomes a screen for presentations. A museum surface that alternates between transparency over the exhibit and projected storytelling, woven into a wider interactive communication journey.

Where smart glass is used

The versatility of switchable glass makes it suitable for many settings, each with a specific benefit linked to privacy, flexible use of space or communication.

Offices and meeting rooms

In offices, smart glass partition walls make it possible to have bright, open spaces that can nonetheless be made private at the touch of a button when a confidential meeting is taking place. The same pane, turned opaque, can serve as a screen for presentations, doing away with the need for a separate projection screen.

Showrooms, shops and hotels

In retail and hospitality, smart glass combines aesthetics with function. A shop window can alternate between a clear view of the product and projected video content; in hotel rooms a bathroom wall can switch from transparent to opaque for privacy; a lounge area can change its configuration to suit the event. These are natural applications for anyone designing spaces for shops, hotels and showrooms, where the element of surprise and attention to detail are part of the customer experience.

Fitting rooms in retail

In retail, smart glass fitting rooms have become a popular solution: the door or wall is transparent when the room is free and turns opaque when occupied, providing instant privacy without curtains. It is a detail that signals modernity and care, and it also makes managing the space easier.

Museums and cultural spaces

In museums, smart glass is used for display cases and partitions: a case can stay transparent to show an artefact and turn opaque to protect it from light or to host a projection that tells its story. This flexibility fits neatly into museums and culture experiences, where the same surface alternates between a direct view of the work and visual storytelling.

Smart glass film: retrofitting existing glass

It is not always possible, or worthwhile, to replace an entire pane. That is why smart glass also comes in an adhesive film version: the same liquid-crystal layer is produced as a thin film to be applied to glass that is already installed, turning it into a switchable surface without removing any fittings.

This retrofit solution is especially useful when you want to add a privacy or projection function to existing windows, partition walls or shop windows while keeping disruption and installation time to a minimum. The film is applied to the surface and connected to the power supply, and from that moment the glass gains the ability to switch from transparent to opaque exactly like a factory-made switchable pane.

The same considerations seen so far still apply: an electrical connection is required, performance as a screen depends on the quality of the projection and the ambient light, and installation must be carried out carefully to ensure an even, long-lasting result. The choice between a complete pane and a film therefore depends on the context: new builds and bespoke projects tend to favour the integrated sheet, while work on existing spaces finds in the film a fast and effective route.

How to choose

To weigh up the various options, it helps to start from the objective. If privacy is the priority, it is enough to consider switchable glass in its basic function. If, on the other hand, you also want to use the surface as a screen, projection needs to be planned from the outset: the position of the projector, the management of ambient light and the content to be shown. A few practical points are worth keeping in mind:

• Primary function: privacy only, projection only or both. The whole design follows from this.
• Pane or film: an integrated sheet for new installations and bespoke projects, an adhesive film for retrofitting existing glass.
• Lighting conditions: if the surface is also to act as a screen, the best results come in spaces with controlled lighting or in the evening.
• Electrical system: smart glass requires a power supply and a control system, both to be planned at the design stage.
• Integration: how it works with the other elements of the space and with any interactive content.

Designing a surface that brings together privacy, architecture and projection benefits from a joined-up perspective, one that ties the glass to the light, the content and the experience of the people moving through the space.