Yes, aluminum sets off metal detectors, almost every time. It is non-magnetic, which surprises a lot of people, but a metal does not need to be magnetic to be detected. A metal detector responds to any metal that conducts electricity, and aluminum is a very good conductor, about 61 percent as conductive as copper. Foil, cans and pull tabs all give a clear signal on a hobby detector, and cans, foil packs and laptops are all metal a security scanner can see.
Why Aluminum Is So Easy to Detect
A metal detector's coil sends out an alternating magnetic field. Any conductive object inside that field develops small circulating currents, called eddy currents, and those currents create a magnetic field of their own that the coil picks back up. How strong that return signal is depends on three things: how well the metal conducts, how big and flat the piece is, and how close it is to the coil. Aluminum scores well on the first two, so even thin, light pieces like foil, can slaw and pull tabs give a solid signal.
Magnetism only matters for part of the story. Iron and steel are both magnetic and conductive, and most hobby detectors use that difference to tell iron apart from other metals. Aluminum, copper, silver and gold are all non-ferrous, so a detector picks them up through conductivity alone.
Will Aluminum Set Off Airport and Stadium Metal Detectors?
Yes. Walk-through scanners and handheld security wands work on the same principle as a hobby detector, just tuned to scan people instead of soil. Aluminum cans, foil-wrapped food, e-cigarettes, laptops and foil-lined packaging are all metal the scanner can see. Wrapping something in foil does not hide it either. The foil is a strong target on its own, so it adds to the signal instead of blocking it.
Whether a walk-through unit alarms depends on how much metal passes through and how the venue has set it up. A full can or a foil pack is a large target, and anything that alarms gets checked with a handheld wand, which picks up even small foil at close range.
How Aluminum Reads on a Hobby Metal Detector
On a hobby detector, aluminum is not one reading. Where it lands on the target ID scale depends mostly on the size and shape of the piece. The exact numbers change from brand to brand, so the table below uses the low, middle and high parts of the scale. Our target ID chart has typical numbers for common finds.
| Aluminum item | Typical target ID | What else reads there |
|---|---|---|
| Thin foil and gum wrappers | Low, just above iron | Thin gold chains and small earrings |
| Pull tabs and pop tops | Middle of the scale | Many gold rings and nickels |
| Can slaw (torn can pieces) | Jumpy, low to middle | Odd shapes give unstable numbers |
| Whole or crushed cans | Often high, sometimes erratic | Can read close to coin range |
Every detectorist learns this the hard way: aluminum trash is the most-dug false treasure in the hobby. Pull tabs and can pieces read in the same middle range as gold rings, which is exactly why experienced ring hunters dig them anyway. Our post on pull tabs and pop tops covers the different styles and how they read.
What This Means in the Field
- Expect aluminum anywhere people have been: parks, beaches, curb strips and fairgrounds.
- Don't notch out the whole pull tab range. Gold rings live there too. If you use notch at all, take out only the one or two numbers your local tabs read most often; our post on notch discrimination explains how notching works.
- Check the signal from two directions. Foil and can slaw often give a jumpy number or break up when you swing across them at a right angle, while a ring usually holds a steadier number.
- Recover fast. A pinpointer gets small foil out of the hole quickly so you can move on.
- More target ID resolution helps, up to a point. Metal detectors with more ID numbers and good target separation let you make better guesses before you dig, but no machine sorts foil from gold perfectly.
The Bottom Line
Aluminum will set off nearly any metal detector. That is physics, not a fault. In the park or on the beach, the skill is learning to live with it: read the target ID, check the signal from more than one direction, and dig the mid-range signals when you are hunting gold jewelry. If you are choosing a machine, our detector finder is a good place to start.
