Short answer: Clear acrylic transmits 92% of visible light (ASTM D1003), and it stays at 92% from thin sheet to thick because it absorbs less than 0.5% per inch; that's slightly more than ordinary clear glass, which is about 90% at 1/8 in. and 83% at 3/4 in. White translucent acrylic transmits about 31 to 54% at 1/8 in. and less in thicker sheet, which makes it the usual face for light boxes and backlit signs. Gray and bronze tints range from about 8 to 48% depending on the shade, and opaque colors pass 0 to 7%.
Transparent, translucent, and opaque
- Transparent sheet lets light straight through, so you can see clearly through it. Clear, tinted (gray, bronze), fluorescent, and transparent colors are in this group.
- Translucent sheet lets light through but scatters it, so you can't see through it. White translucent and frosted sheet are in this group.
- Opaque sheet blocks light. Black, opaque white, and solid colors are in this group.
Light transmission is the percentage of visible light that makes it through the sheet, measured by manufacturers to ASTM D1003 or similar lab methods, so treat published numbers as a guide rather than an exact match for your sign.
Typical light transmission by sheet type
| Sheet | Light transmission | Notes |
|---|---|---|
| Clear acrylic (Acrylite, Optix) | 92% | Same at every thickness; nearly all the loss is reflection at the two surfaces |
| Non-glare clear (Acrylite P99) | 90% | Fine matte texture on one side |
| Frosted (Acrylite Satinice, colorless) | 88 to 92% | One-sided 92%, two-sided 88 to 89%; scatters light but doesn't hide LEDs as well as white |
| White translucent, light-box grade (2447 type) | 53 to 54% at 1/8 in. | 43% at 3/16 in., 35% at 1/4 in. (Acrylite extruded) |
| White translucent, sign white (7328 type) | 31 to 32% at 1/8 in. | 23% at 3/16 in., 18% at 1/4 in. |
| Gray tints | 8 to 25% | Acrylite 2064 gray 25%, 2074 gray 13% |
| Bronze tints | 11 to 48% | Acrylite 2404 bronze 48%, 2412 27%, 2370 11% |
| Fluorescent colors | 41 to 94% | Transparent; edges glow |
| Opaque white | 2 to 7% | Thin opaque white may glow faintly with strong light behind it |
| Opaque black | 0% | Used for masks, backs, and blocking light |
Figures are from Acrylite's color chart and light transmission data (3 mm unless noted) and Plaskolite's product guide; other brands and colors differ. If an exact percentage matters, ask for the data sheet for the specific product, or test a sample with your actual lights.
Does thickness change light transmission?
It depends on the sheet:
- Clear: no. Acrylite says colorless acrylic absorbs less than 0.5% of visible light per inch, and all thicknesses transmit 92% from 395 to 1,000 nm.
- White translucent: yes, a lot. The pigment level stays the same at every thickness, so 1/4 in. passes about two-thirds of what 1/8 in. does, or less.
- Transparent colors and tints: usually not. Acrylite adjusts the dye level by thickness so its colored sheet has the same transmission at every thickness. Check the data sheet for other brands.
Why clear acrylic is 92%
Whenever light passes from air into a clear material, a little reflects off the surface: about 4% at each face of acrylic. Two faces lose about 8%, which leaves 92%. Light arriving at a steep angle reflects more: Acrylite says that under evenly bright sky light from all angles, clear sheet transmits about 85%. The acrylic itself absorbs very little, so a 1 in. sheet looks almost as clear as a 1/8 in. one. Ordinary glass contains iron, which gives a green edge and absorbs more as it gets thicker: Vitro gives clear glass about 90% at 1/8 in. and 83% at 3/4 in., and low-iron glass about 91% and 90%.
Choosing acrylic for a light box or backlit sign
For a light box, you want two things that pull against each other: brightness and evenness. A sheet that passes a lot of light also tends to show each LED as a bright dot. A sheet that hides the LEDs completely passes less light.
- White translucent is the standard face for light boxes and backlit signs. It hides the light source and looks solid white when off and glowing when on.
- Higher-transmission whites (2447 type, or LED grades around 65%) suit shallow boxes and lower-power lighting but may show hot spots, and can look grayish in daylight when unlit.
- Lower-transmission whites (7328 type) hide LEDs better and look whiter in daylight: Acrylite measures 89% reflectance for its 7328-type over a white backing, but they need more light behind them.
- Depth matters as much as material. As a starting point, keep the LEDs at least as far from the face as they are from each other. The deeper the box, the more even the light.
Printed vinyl or film on the face cuts the light further, so allow for that when choosing a bright enough grade.
Choosing acrylic for LED diffusers
For LED strip channels, under-cabinet lights, and panel lights, white translucent gives the smoothest line of light. Frosted sheet keeps more brightness but shows more of the individual LEDs at close range. See acrylic LED light diffusers for sizes and ideas, and compare frosted options in frosted acrylic options.
What about edge-lit signs?
Edge-lit signs use clear acrylic, not translucent. The light enters the edge and travels through the sheet, and engraving on the face makes the design glow. Clear's very low absorption is what lets the light reach the far side of the sign; Acrylite recommends highly polished edges and bends no tighter than three times the sheet thickness for light piping. Read how edge-lit signs work or see edge-lit LED sign ideas.
Tinted acrylic for screens and windows
Gray and bronze tints cut glare and brightness while staying see-through, like sunglasses. They're popular for display covers, electronics windows, and sun-facing panels. A 25% gray passes about a quarter of the light; darker shades suit screens that need to hide what's behind them. We stock gray and bronze tint in 1/8 to 3/8 in.
Once you've picked a sheet, we can cut it to size, shape the face of a light box, or route channels for LED strips. See your price instantly in the instant quote.
Questions
Does acrylic let more light through than glass?
Slightly, and the gap grows with thickness. Clear acrylic transmits 92% at any thickness; ordinary clear glass is about 90% at 1/8 in. and about 83% at 3/4 in., and it has a green tint at the edges. Low-iron glass is close to acrylic.
Does thicker acrylic block more light?
For clear acrylic, hardly at all. For white translucent, yes: Acrylite's 2447-type white drops from 54% at 1/8 in. to 35% at 1/4 in. Most transparent colors are made to transmit the same at every thickness.
Will acrylic's light transmission drop over time?
Very little. Acrylite warrants its clear cast sheet to lose no more than 3% of its light transmission in 30 years. Scratches and dirt cause more loss than aging. Does acrylic turn yellow?
What's the difference between 7328 and 2447 white acrylic?
They're industry color numbers for two white translucent densities. 7328 passes about 31 to 32% at 1/8 in. and looks bright white unlit; 2447 passes about 53 to 54% for brighter backlighting but looks slightly gray when off.