EL Posters for Retail Windows: A Buyer’s Brief

The problem in one line: a shop window has two lighting states, day and night, and most EL disappointments come from specifying for the wrong one.

We print and laminate EL posters in Foshan for window campaigns in leased shopfronts, malls and pop-ups. This brief covers the practical decisions: measuring the window, sizing to the glass, hiding the inverter, mounting without drilling, and judging daytime performance honestly. For the raw brightness numbers behind this page, the brightness explainer covers the 80-140 nits band and drive settings.

Quick facts: EL posters for retail windows

What an EL poster for a retail window actually is

It is a printed light source, not a backlit picture. Seven thin layers stack into a panel you can roll, cut to shape and tape to glass. From the viewing side they run: printed graphic film with a laminate, clear PET base, transparent ITO electrode, silver bus bars, a phosphor layer doped with copper, a dielectric layer, and a rear electrode.

The panel glows across its whole face when an inverter pushes alternating current through it, typically 100-200V at 400-2,000 Hz. The inverter takes 3V, 5V, 12V or mains input. Nothing in the stack is hot: the surface stays near room temperature, which matters when a silk scarf hangs 40 mm away.

Two numbers describe it inside a window. Luminance, measured in nits, is how bright the face is: 80-140 nits on our line. Illuminance, measured in lux, is how much light falls on everything else in the window. A buyer who confuses the two will specify a poster that looks perfect at 21:00 and invisible at 13:00.

Thickness and weight are the quiet advantages. A 0.4 mm panel adds no box cavity, so the window keeps its full depth for product. At under about 1 kg per square metre it hangs from tape or suction cups, which means no drilling in a leased shopfront and no landlord conversation.

Why window buyers care about the glow

The window is the most expensive square metre in the store. Rent is priced on frontage, and the glass is the only surface that talks to people who never walk in. A poster that adds light after dark extends the selling day past closing time.

Depth is merchandise space. A light box 40-60 mm deep eats the window. A laminated panel takes less than a millimetre, so a mannequin can stand where the box used to be.

Campaigns rotate. Fashion, cosmetics and pharmacy windows refresh every 4-8 weeks. A thin panel ships flat or rolled, stores in a drawer, and returns next season without a crate.

Heat is a merchandising risk. Spot lamps aimed at a window can cook chocolate, cosmetics and printed cartons. EL runs cold, so it can sit close to product without a heat budget.

Leases forbid drilling. Most mall and high-street leases do. Tape, suction and standoffs solve the installation question before it reaches the landlord.

How a window build works, layer by layer

The glow competes with the room. Your eye judges the poster against whatever sits beside and behind it. A 120-nit face against a dark backing reads bright. The same face against a white wall lit to 2,000 lux reads as a pale tint. Position and surround decide more than the panel does.

Glass adds a second image. Clear float glass reflects roughly 4-8% of the scene in front of it. At eye level that reflection lands on top of your poster. Tilting the panel a few degrees, or moving it 150-200 mm back from the glass, pushes the reflection off the sightline.

Power has a path. The inverter is a small box, usually 60-90 mm long, that must stay dry and ventilated. In a window it hides in the sill return, behind the base deck, or in a shallow trunking along the mullion. Cables run vertically, never diagonally across the glass.

The glass traps heat. A south-facing window can run 10-15C above street temperature in summer. Heat accelerates phosphor fade, so shade the panel from the direct sun path and specify a UV-blocking laminate.

Mounting is mechanical, not adhesive guesswork. Reclosable fastener tape for flat glass, suction cups for a two-week campaign, clear standoffs for a permanent install, and a slim aluminium frame when the client wants a finished edge.

Where EL posters earn their place in a window

EL poster vs LED light box vs printed window graphic

When an EL window poster is worth it – and when it is not

How to choose the right window build

1. Measure the glass and the sightline. Note width, height, sill height and the distance from the glass to the far pavement. A window read from 8 m needs different lettering than one read from 2 m.

2. Measure light at the poster plane, three times a day. Take readings at 10:00, 14:00 and 20:00. A phone lux app is enough for a first look; use a meter before a chain rollout. The 14:00 figure is the one that decides feasibility.

3. Size to the sightline, not the frame. Leave 150-200 mm of glass around the panel. Set headline cap height at about 5 mm per metre of viewing distance, and double it for comfortable reading from across the street.

4. Decide the power path before the artwork. A socket with a timer is the simplest. No socket means a battery box or USB pack in the sill. Tell us the lit hours per day and we set the drive preset accordingly.

5. Pick the mounting that matches the lease. Two-week campaign: suction cups. Season: reclosable tape. Permanent: standoffs or a slim frame. All three avoid drilling.

6. Design for the medium. Dark or mid-tone background, one saturated brand colour, strokes of 3-4 mm at final size, no thin serifs, no pastel gradients on white. A design that works on paper can disappear on a glowing face.

7. Follow the sample sequence. Artwork review, animation map where zones are used, mockup, physical sample, written approval, then production. Sample within 7 days of mockup approval, standard runs 7-10 days, larger bulk 15-20 days.

Common mistakes in window installs

Judging from a phone photo. Cameras expose for the glow, so the room looks darker than it is and the poster looks brighter. Judge in the window, at the hour that matters.

Sizing to the frame instead of the sightline. A panel that fills the glass edge to edge leaves no breathing room and no room for the reflection to fall away.

White artwork on a white field. The glow has nowhere to contrast. Use a dark field or a strong colour block behind the message.

Sealing the inverter in a box. The panel runs cold; the driver does not. Trapped heat shortens driver life long before the phosphor fades.

Running the cable across the glass. It reads as a mistake to every passer-by. Route along the mullion or behind the base deck.

Specifying only for noon or only for midnight. Both states exist. A window brief that names one hour will fail at the other.

Feature, advantage, benefit at a glance

Related reading

Measure before you order

Related products

Choose the build that suits the glass

The bottom line

An EL poster is the thinnest way to put light in a shop window. It wins after dusk, in shaded windows and in leased shopfronts where nobody may drill. It loses to a light box in a sunlit window with 3,000 lux of accent light. Measure the window at 14:00, size to the sightline, hide the inverter, and test a sample in the real glass. Send the window measurements and the lit hours through our contact page and we will reply within the hour with a build, a drive preset and lead times in writing.