License plates are made from aluminum, with a reflective sheeting layer on top and raised characters stamped or embossed into the metal
The base of a standard license plate is aluminum — typically a thin sheet about 0.040 to 0.063 inches thick. Aluminum is chosen because it is lightweight, does not rust, and can be stamped or embossed with raised characters that are difficult to alter. The metal itself is usually an alloy that balances durability with the ability to hold a clear impression when the numbers and letters are pressed into it.
On top of the aluminum sits a layer of reflective sheeting, usually made from a microprism or glass-bead material. This sheeting is what makes your plate glow when headlights hit it at night — a safety feature that lets other drivers see your plate from a distance. The reflective layer is bonded to the aluminum with an adhesive, and the characters are then applied on top of that. Different states use different colors and reflective qualities, but the principle is the same across all of them.
The characters themselves — your numbers and letters — are typically made from a retroreflective material that contrasts with the plate background. On a white plate with blue characters, for example, the characters are made from a material that reflects light differently than the white background, making them stand out both in daylight and at night. Some states use raised metal characters that are separate pieces attached to the plate, while others use flat characters printed or embossed directly into the reflective layer.
Key Takeaways
- License plates are aluminum sheets with a reflective coating that makes them visible to other drivers at night.
- The reflective layer uses microprism or glass-bead technology to bounce light back toward its source, a safety feature required by federal standards.
- Characters are either raised metal pieces or printed directly onto the reflective surface, and they are designed to resist tampering and fading.
- The specific materials and construction methods vary by state, but all plates must meet minimum reflectivity and durability standards set by the American Association of Motor Vehicle Administrators.
Why aluminum instead of steel or plastic
Aluminum was chosen over steel because it does not corrode in salt air or road salt, a major concern in northern states where roads are salted in winter. Steel plates would rust through within a few years in those conditions. Plastic has been tested and rejected because it does not hold a clear, permanent impression when characters are stamped into it, and it degrades under UV exposure from sunlight.
Aluminum also has a lower density than steel, which means a plate is lighter and easier to handle during manufacturing and installation. The metal is soft enough to be stamped cleanly but hard enough to resist bending or warping when bolted to a vehicle. The alloy composition — usually containing manganese and magnesium — is tuned to balance these properties.
How the reflective layer works and why it fades
The reflective sheeting works by using thousands of tiny prisms or glass beads embedded in a plastic film. When light from a headlight hits these prisms at night, they bend the light back toward the source — toward the driver who is looking at your plate. This is why a license plate is bright and readable from far away at night, even though the plate itself produces no light.
Over time, the reflective layer degrades. UV rays from the sun break down the plastic binder that holds the prisms or beads in place. Road salt, road tar, and cleaning chemicals can also damage the surface. After 5 to 10 years, depending on climate and how often the plate is cleaned, the reflectivity drops noticeably. This is why many states require plate replacement every 5 to 7 years — not because the aluminum fails, but because the reflective coating no longer meets safety standards.
Some states now use high-intensity reflective sheeting, which uses a more durable resin and larger prisms. These plates stay reflective longer but cost more to produce. Other states use standard reflective sheeting and accept more frequent replacement as the cost of doing business.
The raised characters and anti-tampering design
The numbers and letters on your plate are raised — pressed or stamped outward from the surface — for a specific reason: it makes the plate harder to alter. If someone tries to file down a character or cover it with a sticker, the raised edge is visible and the tampering is obvious. Flat characters printed onto the surface would be easier to obscure or modify.
The characters are typically made from the same retroreflective material as the plate background, but in a contrasting color. A blue character on a white plate reflects light differently than the white background, which makes the character stand out in both daylight and darkness. The height of the raised characters is standardized — usually between 0.15 and 0.25 inches — so that they are readable from a legal distance (usually 75 feet for law enforcement).
Some states now use embossed characters instead of raised metal pieces. Embossing presses the character shape into the reflective layer itself, creating a depression or raised area that is part of the plate rather than a separate attachment. This method is faster to produce and eliminates the risk of a raised character coming loose or being pried off.
Durability standards and what "meets code" means
All license plates sold in the United States must meet standards set by the American Association of Motor Vehicle Administrators (AAMVA). These standards specify minimum reflectivity levels, character height and spacing, color combinations, and material composition. A plate that "meets code" has been tested to may support that it reflects light at a certain brightness level and that the characters remain readable after exposure to UV light, salt spray, and temperature cycling.
The reflectivity is measured in candelas per lux per square meter (cd/lux/m²). Standard reflective sheeting typically achieves 75 to 100 cd/lux/m², while high-intensity sheeting reaches 150 to 200 cd/lux/m². These numbers tell you how bright the plate will appear when headlights hit it. A higher number means the plate remains readable from farther away and in worse weather.
Durability testing includes salt-spray chambers (which simulate years of road salt exposure), UV exposure chambers (which simulate years of sunlight), and thermal cycling (which simulates freeze-thaw cycles). A plate that passes these tests is expected to maintain its reflectivity and character legibility for the duration of its service life — typically 5 to 10 years depending on the state and the sheeting type used.
Why some plates look different: specialty materials and finishes
Not all plates are made the same way. Vanity plates, personalized plates, and specialty plates (such as those for disabled drivers or veterans) may use different materials or finishes. Some states offer plates with a textured or embossed background, which can improve reflectivity or straightforward change the appearance. Others offer plates with a clear protective coating over the reflective layer, which can extend the life of the plate by protecting the sheeting from UV and chemical damage.
Temporary plates — the paper or cardboard plates issued when you buy a new vehicle — are made from a completely different material. They are printed on heavy paper or cardstock with reflective ink, and they are designed to last only a few weeks until your permanent plate arrives. These temporary plates do not meet the same durability standards as permanent plates because they are not expected to be in service for years.
What happens when a plate is damaged or faded
If your plate becomes dented, cracked, or so faded that the characters are hard to read, you should have it replaced. A damaged or illegible plate can result in a traffic stop, and in some states, it is technically a violation to display a plate that does not meet reflectivity standards. Replacement plates can usually be ordered through your state's motor vehicle department, either online or in person at a local office.
The cost of replacement varies by state — typically between $5 and $30 for a standard plate — and the process usually takes 1 to 3 weeks. Some states offer rush processing for an additional fee. If your plate is stolen, you should report it to your local police and then contact your motor vehicle department to request a replacement with a new number, since a stolen plate can be used to commit fraud or evade tolls.
Frequently Asked Questions
Can I clean my license plate with any cleaner, or will it damage the reflective coating?
Use mild soap and water or a glass cleaner. Avoid abrasive scrubbers, harsh chemicals like bleach, or high-pressure washers, which can damage the reflective layer. Dry with a soft cloth. The reflective sheeting is durable but not indestructible, and aggressive cleaning can shorten its life.
Why do some plates look shiny and others look dull?
The difference is usually the type of reflective sheeting used. High-intensity sheeting has a shinier, more mirror-like appearance and reflects light more brightly. Standard sheeting looks duller and less reflective. Some states use one type for all plates; others offer high-intensity as an upgrade. The dull appearance does not mean the plate is damaged — it is just a different material.
What is the metal plate made of if it is not aluminum?
In the United States, standard license plates are aluminum. Some specialty or vintage plates may use steel or other metals, but aluminum is the federal standard for new plates. If you have an older plate from decades ago, it may be steel, which is why those plates often show rust.
How long does a license plate actually last before it needs to be replaced?
The aluminum base can last 20+ years, but the reflective coating typically degrades after 5 to 10 years depending on climate and sun exposure. Most states require replacement every 5 to 7 years to may support the plate meets reflectivity standards. Your state's motor vehicle department can tell you the replacement schedule for your area.
Can I repair a cracked or bent license plate, or do I have to replace it?
Minor dents usually do not affect the plate's function or legality. A cracked plate should be replaced because the crack can spread and eventually make the characters illegible or cause the reflective layer to peel. Welding or gluing a cracked plate is not a reliable fix and may not meet legal standards.