Window Tint Explained: Film Types, Tint Percentages and California Tint Law

A tint percentage is the film's visible light transmission (VLT): "the percent of visible light that is transmitted (passes through) a glazing system", in the International Window Film Association's words (IWFA). The lower the number, the darker the window. A 5% "limo" film passes a twentieth of the light; a 70% film looks close to factory glass. So 20% is darker than 35%, and 35% darker than 50%.

Two things move the number you end up with:

• The glass. "All automotive glass is tinted to some extent" (IWFA), and film adds to it. On 3M's 73% reference automotive glass, its Ceramic IR 70 film reads 64% and its Ceramic IR 35 reads 37% (3M). A tint meter reads glass and film together, and that is the figure the law looks at.
• The name. The number on the box is a product name, not a reading on your car.

Darkness buys privacy and glare control; it does not measure heat. On LLumar's own sheet, measured on 6 mm clear glass, its light CTX 50 ceramic film rejects 43% of the sun's total energy, about the same as its near-black ATC 05 dyed film at 44% (LLumar). How 5, 20, 35 and 50% look by day and at night, and whether to pick 35 or 50: is 35 or 20 tint darker.

Every car film is a polyester base with a performance layer, a scratch-resistant coating and an installation adhesive (IWFA); 3M's films go on the inside of the glass with a pressure-sensitive acrylic adhesive (3M). The performance layer names the type: dye in dyed film, a thin aluminum layer in metallized, carbon particles in carbon, and non-metallic, infrared-absorbing nanoparticles in ceramic, which cuts heat at light shades and leaves phone and GPS signals alone. Each type's heat figures and the brands: what is ceramic window tint.

What are tint grades? "Grades" usually means film tiers, from dyed through carbon and ceramic to premium multilayer film, and total solar energy rejected (TSER) is the figure to compare them by. Near the 35% shade, on each maker's sheet for 6 mm clear glass: LLumar ATC 35 dyed rejects 35% and its CTX 35 ceramic 48% (LLumar); SunTek CXP 35 carbon, 53% (SunTek). The tiers overlap, so compare the film, not the label; every film's figures are in the heat table. Shade is a separate choice: each tier comes in several.

Can ceramic tint be removed? Yes, slowly, with care at the back glass: see how old window tint is removed.

• Rear side windows: any shade, down to 5% (26708(b)(4)).
• Back glass: any shade, if outside mirrors on both sides show the road behind (26708(b)(8)).
• Front side windows: clear, colorless film of 88% or more only. Glass and film together must still pass 70%, and the installer's certificate stays in the car (26708(d)).
• Windshield: a strip at the top, its bottom edge at least 29 inches above the driver's seat (26708(c)).

Is 15% tint legal in LA? On the rear side windows and back glass, yes; on the front side windows, no. The rules are state law: the Vehicle Code bars cities and counties from making their own rules on matters it covers (VC 21), so Los Angeles, Long Beach and Pasadena follow the same lines.

Can you tint a leased car? The law is the same; the lease may not be: see how to have tint legally in California.

Medical letters, tint meters, ticket costs and out-of-state plates: how to have tint legally in California.

Among the benefits of car film, the IWFA lists appearance, solar heat reduction, UV protection and glare control. It earns most on a car that sits in the sun. The costs are a darker view out at night with dark film and, in California, front side windows that stay clear whatever you choose. The trade-offs, ceramic included: the downsides of ceramic tint.

Film goes on wet, inside the glass, and a heat gun shrinks it to fit curved glass such as the back window (3M). A careful installer meters the bare glass before and the finished window after. At a shop or where the car is parked, the spot needs shade, no wind or dust, and a temperature inside the film's working range: 4–45°C (39–113°F) for 3M's Color Stable film. What a home or office install needs: mobile window tinting; for the house itself, home window tinting.

Why film bubbles, peels or turns purple, and how long it lasts: how long does window tint last.