What a fridge magnet is made of, and which kind you are buying

Flexible magnetic sheet is ferrite powder, a ceramic compound based on iron oxide, mixed into a rubber or polymer binder and extruded into long rolls. The ferrite supplies the magnetism; the binder is what lets a sheet as thin as 0.4 mm bend around a corner without cracking, something a block of solid ceramic magnet could never do. This is the base material under almost every printed promotional magnet handed out from a takeaway counter or an estate agent's window.

Why the sheet is striped

The roll passes through a magnetiser that lays down narrow bands of alternating north and south poles across its width. That striping is why two sheets of the same material can repel each other in some orientations and grip strongly in others, and why holding power drops off sharply once there is any gap between the magnet and the door. The field from each stripe reaches only a few millimetres before curving back to the next stripe of opposite polarity, so contact with the steel matters more than most people expect.

What this means for the finished magnet

Because the striping concentrates the field close to the surface, holding power depends heavily on how thick the sheet is. The standard thicknesses are 0.4 mm, 0.6 mm, 0.75 mm and 0.85 mm, and a thicker sheet holds more because it packs in more stripe pairs. Not every printer stocks all four, so confirm with your printer which thickness they run before you commit to a size. The printed face on top, whether laminated paper or direct-printed vinyl, adds nothing to the magnetic strength; it sits on this base and carries the design alone.

For a working comparison of thickness against what each will realistically hold on a vertical fridge door, see Will It Stick? Magnet Strength, Thickness and What It Can Hold.

Four other magnet materials turn up behind printed and souvenir magnets, alongside the flexible magnetic sheet covered elsewhere on this page. Each behaves differently on a fridge door, and each is bonded to a printed face in a different way.

Hard ferrite

Hard ferrite is a ceramic magnet material made by sintering iron oxide with strontium or barium carbonate into a solid block or disc, then magnetising it. It is rigid, and it sits behind most souvenir magnets and pin-badge clips. Domain alignment in a sintered ceramic disc is tighter than in ferrite powder dispersed through a rubber binder, so a small hard ferrite disc holds considerably more weight than a flexible sheet magnet of the same footprint. That extra pull matters because souvenir magnets are usually heavier, carrying a resin dome or a cast metal body.

Neodymium

Neodymium (NdFeB) is the rare-earth magnet material and the strongest in common use. A neodymium disc only a few millimetres across can outpull a hard ferrite disc several times its size, which is why it turns up behind premium photo magnets and small souvenir pieces where the visible magnet needs to stay discreet. The same strength is the reason neodymium magnets carry a specific safety position for households with children, covered in full on Small Magnets, Children and Pets.

Alnico

Alnico is an aluminium-nickel-cobalt alloy magnet, once the standard magnet material before ferrite and neodymium became cheaper to produce. It holds up well at high temperatures and resists demagnetising, but for a given volume it pulls less than neodymium and less than hard ferrite. Alnico is uncommon in current promotional and souvenir ranges, and where it does appear it is usually in older or novelty pieces.

Epoxy dome construction

An epoxy dome is a clear resin dome bonded over a printed insert, the construction behind most tourist souvenir magnets. The image is printed flat, cut to shape, and a hard ferrite or neodymium disc is glued to the back before the whole assembly is sealed under the raised resin dome. The dome protects and magnifies the print but plays no part in holding the magnet to the door; that job belongs entirely to the disc underneath.

Acrylic photo magnets

An acrylic photo magnet mounts a printed photograph behind a flat clear acrylic block. A magnet disc is bonded to the back in the same way as an epoxy dome piece. The choice between the two is largely about finish: a dome reads as a rounded souvenir piece, an acrylic block reads as a flatter, more photographic object.

Die-cut shapes and resin or metal souvenir bodies

Die-cut means the trim follows the outline of the printed shape, and it can apply to flexible sheet magnets as well as to insert-based ones. Where artwork is cut to a shape, the printed area still needs to run past the finished edge so trimming variation does not leave a pale border; check that your artwork meets the size and resolution the cutter needs using the Artwork Size and Resolution Checker. Cast metal souvenir magnets use a zinc alloy body, often filled with coloured enamel, with the magnet disc glued or recessed into the back; full resin constructions cast the whole body in resin around a sealed paper insert. Both are covered from the collecting side in Collecting Souvenir Magnets.