Beer cans are made from aluminum, but not a single type. The body and the lid use two different aluminum alloys, and the inside is lined with a thin polymer coating that keeps your beer from ever touching the metal. There’s more engineering in a beer can than most people realize.
The Two Alloys in Every Can
The body of a beer can is made from an alloy called 3004, which contains about 1% manganese and 1% magnesium mixed into the aluminum. Those additions strengthen the metal enough that the walls can be made extremely thin without collapsing. A finished beer can wall is only about 0.270 mm thick, roughly the width of three sheets of paper.
The lid is a different story. It needs to be significantly stronger so the pull tab mechanism works reliably every time. Lids are stamped from alloy 5182, which has 4.5% magnesium and 0.3% manganese. That higher magnesium content gives the lid the strength to handle the scored opening, the rivet holding the tab, and the stress of being pulled open without tearing unpredictably.
How a Flat Disc Becomes a Can
A beer can starts as a flat circular piece of aluminum. Through a process called deep drawing, a machine punches that disc into a shallow cup shape. Then, in a series of ironing stages, the cup is pushed through progressively tighter rings that stretch the walls thinner and taller while keeping the diameter constant. The bottom stays relatively thick for structural support, while the sidewalls get drawn out to their final paper-thin dimension. This is why beer cans feel so light yet hold their shape under the pressure of carbonation.
The result is a “two-piece” can: one piece forms the body and bottom, and the lid is a separate piece seamed on after filling.
The Invisible Coating Inside
If beer sat directly against bare aluminum, the acids in it would corrode the metal, changing the taste and dissolving aluminum into your drink. Every beer can has a thin polymer lining sprayed on the inside to act as a barrier between the beverage and the metal.
For decades, this lining was an epoxy resin based on bisphenol A (BPA). BPA-based epoxies became standard in beer cans starting around 1960 and dominated the industry for over 50 years. In recent years, health concerns around BPA have pushed manufacturers toward alternatives. The vast majority of can coatings applied today are BPA-free, using materials like acrylic, polyester, or non-BPA epoxy formulations instead.
Even with a liner, some interaction between beer and can is possible over time. Research from the Journal of the American Society of Brewing Chemists found that dissolved aluminum levels correlate with acidity, and that organic acids like lactic and acetic acid (common in sour beers) can promote corrosion even through lined cans. This is one reason sour and highly acidic beers sometimes use thicker liner formulations recommended specifically for corrosive beverages.
The Exterior: Ink, Varnish, and Color
The colorful labels on beer cans aren’t paper stickers. They’re printed directly onto the aluminum using specialized inks that contain UV-curable compounds and organic solvents. After the image is printed (increasingly by high-speed inkjet systems), it’s hit with UV light to partially cure and “pin” the ink in place so it doesn’t smear. Then a clear overprint varnish is rolled over the entire can and the whole thing goes through a final heat cure. This layered process gives cans their glossy, durable finish that resists scratching and moisture.
The Tab That Stays Attached
The stay-on tab you use to open a beer can has its own design history. Early cans used pull-off tabs that created litter and injury problems. In 1958, inventor Anthony Bajada patented the first design that kept the tab connected to the lid. After that patent expired in 1975, engineers at Reynolds Metals and elsewhere refined the concept into the modern stay-tab design that became universal by 1990.
Today’s opening mechanism is more sophisticated than it looks. The lid has a scored line that defines the opening, plus a small indentation that concentrates stress exactly where the crack needs to start when you lift the tab. The crack travels in two directions along the scored path, then stops at engineered endpoints. The freed section folds down into the can on a small metal hinge rather than detaching, so nothing separates from the lid.
Recycled Content and Sustainability
Aluminum cans are one of the most recycled consumer packages, and new cans are made largely from old ones. The average aluminum beer can made in the U.S. contains about 71% recycled material. That number has actually dipped slightly from 73% in 2019, and overall aluminum can recycling rates in the U.S. are at their lowest point in decades. Still, 71% recycled content far exceeds the rate for glass bottles and plastic containers. Recycling aluminum uses roughly 95% less energy than producing it from raw ore, which is why the industry has pushed recycling as a core part of its sustainability pitch.