Magnetic sheet or neodymium magnet? The comparison for geocaches
The short answer: A neodymium magnet holds much more strongly than magnetic sheeting and is therefore the first choice if your cache really needs to hang securely, for example as a nano on a screw, as a PETling under a railing, or as a container on an electrical box. Magnetic sheeting is weaker, but flat, flexible, and easy to print on. It plays to its strengths when you want to camouflage a smooth steel surface, for example with an inconspicuous sign or a flat logbook hiding place. Here you will find out exactly where the differences lie, which sheeting is suitable for geocaching, and how to mount both options so that they still hold after the third winter.
Key Findings
- Magnetic force: Neodymium material holds many times more than ferrite magnetic sheeting. For magnetic tapes, neodymium types range from 150 to over 400 g/cm², while ferrite types range from 20 to 45 g/cm².
- Camouflage: Magnetic sheeting is flat, cuttable, and can be coated or covered in color. This makes it ideal for flat camouflage shields on steel.
- Weather: Neodymium is an iron alloy and needs a good coating or an enclosed housing outdoors. According to the manufacturer, ferrite magnetic sheeting can withstand approximately −15 to 70 °C.
- Rule of thumb: For hiding places that carry weight or are frequently touched, use neodymium. For flat camouflage surfaces without much load, use magnetic sheeting.
- Safety: Small neodymium magnets should not be in children's hands. Swallowing several magnets can be life-threatening.
Table of Contents
- What magnetic sheeting and neodymium magnets actually are
- Magnetic force in direct comparison
- Outdoors, more than just magnetic force counts
- When magnetic sheeting is the right choice
- When a neodymium magnet clearly wins
- Decision aid for your hiding place
- Mounting in five steps
- Our view from the cache workshop
- Ready-made magnetic hiding places from CacheWerk
- Frequently Asked Questions
- Sources
What magnetic sheeting and neodymium magnets actually are
Both terms appear in every DIY forum, but describe completely different materials.
Magnetic sheeting consists, according to the manufacturer Beloh, of strontium ferrite powder and an elastic binder. The powder is therefore embedded in a kind of plastic mat. This is why you can cut the sheeting with scissors, bend it easily, and remove it again and again. It adheres directly to sheet steel and all ferromagnetic surfaces. Advertising technicians use it exactly for this: Motifs can be attached and removed without compromising adhesion.
Neodymium magnets, on the other hand, are compact metal parts. The material is an alloy of neodymium, iron, and boron, or NdFeB for short. These magnets are among the strongest permanent magnets available. Even a disc the size of a shirt button can securely hold a cache to a lamppost. The catch: The material is hard and brittle and tends to splinter when machined. Drilling, grinding, or filing is therefore out of the question.
In between, there is a hybrid form: neodymium magnetic sheeting. According to Haas Magnettechnik, it contains neodymium-iron-boron powder in a plastic binder. It is significantly stronger than ferrite sheeting, but stiffer, and it loses approximately 2% of its magnetic force for every 10 °C above 30 °C. For a cache glued to a sunny electrical box in summer, this is a value you should know.
Magnetic force in direct comparison
A data sheet for magnetic tapes shows how large the difference is: Flexible neodymium tape with a thickness of 0.6 to 1.5 mm provides 150 to over 400 g/cm². Standard ferrite tape of a similar thickness provides 20 to 45 g/cm². That is roughly a factor of ten.
In practice, this means: A piece of ferrite magnetic sheeting the size of a business card (around 45 cm²) can theoretically support one to two kilograms, but only if it lies flat on smooth, clean steel. As soon as paint, rust, a bulge, or an air gap is added, the value drops quickly. A neodymium magnet concentrates its force on a tiny area and still holds even if the surface is not perfect.
| Property | Magnetic sheeting (ferrite) | Neodymium magnet |
|---|---|---|
| Material | Ferrite powder in a flexible binder | Neodymium-iron-boron alloy |
| Magnetic force (tape comparison) | 20 to 45 g/cm² | 150 to over 400 g/cm² |
| Shape | flat, cuttable, flexible | small, rigid, brittle |
| Camouflage | printable, can be coated in color | built into the hiding place |
| Temperature range | approximately −15 to 70 °C | Heat weakens the magnetic force |
| Moisture | suitable for outdoor use | needs coating or housing |
| Typical cache | flat camouflage shield, sheeting micro | nano, PETling, magnetic container, screw hiding place |
Outdoors, more than just magnetic force counts
In the lab, neodymium always wins. Outdoors on a guardrail post, three more opponents come into play: water, temperature, and distance.
Moisture and rust
Neodymium magnets consist largely of iron. That is why they are usually nickel-plated or otherwise coated from the factory. If this layer is damaged during mounting, corrosion begins exactly there. That is why a neodymium magnet is best protected inside the hiding place or is glued in all around. How to coat and mount magnets weatherproofly, we show you in detail in the post Coating and mounting for outdoor hiding places.
Ferrite magnetic sheeting does not rust. According to Beloh, it can be used both inside and outside. For vehicle bodies, the manufacturer recommends a thickness of 0.8 to 0.9 mm and full-surface mounting, without bending the sheeting around edges or trim strips. The same applies to your cache on the electrical box: stick it flat, never bend it over an edge.
Temperature
Magnetic sheeting has clear limits. According to the application instructions from Flyeralarm, it should not be used below −15 °C or above 70 °C, because otherwise it loses its magnetic properties and no longer adheres. In a German winter with frost nights and in midsummer on dark sheet metal, you will certainly come close to these values. The adhesive layer of self-adhesive sheeting also has limits: Beloh calls it permanent up to 50 °C and short-term up to 70 °C.
Distance to the surface
Every millimeter between the magnet and the steel costs magnetic force. Thick layers of paint, shrink wrap, adhesive pads, or dirt act as spacers. With sheeting, you can counteract this: A thin steel backing plate on the back increases the magnetic force by 10 to 50% according to Beloh. With neodymium, it helps to keep the coating thin and to set the magnet flush. If your container still slips, you will find the typical causes in our guide Magnetic container does not hold.
When magnetic sheeting is the right choice
Magnetic sheeting has a fixed role in geocaching: flat, inconspicuous camouflage. Typical use cases are:
- Back sides of traffic signs and steel electrical boxes
- Mailboxes, metal doors, and steel beams
- Railings with a wide, smooth surface
- Combination with a camouflage shield that looks like a maintenance or inspection sticker
The classic magnetic sheeting cache is simple: A piece of thick sheeting, a weatherproof-packaged logbook on the back, and a motif on the front that fits the environment. Because the sheeting is so thin, it hardly stands out. The prerequisite is always a magnetic surface. It does not hold on aluminum, austenitic stainless steel, wood, or plastic.
How to camouflage magnetic sheeting without sacrificing adhesion
The camouflage belongs on the front, never on the magnetic side. Every layer on the back increases the distance to the steel.
- Choose the color from the factory: According to Beloh, magnetic sheeting is available in raw brown, with a white PVC coating, or in colors such as black, gray, green, or red. A welded-on coating prevents the layers from shifting against each other during temperature changes.
- Print or cover the motif: A weatherproof sticker in the color of the surface or a realistic inspection label makes the sheeting practically invisible.
- Cut the edges cleanly: Rounded corners are less likely to come loose in the wind and when being pulled off.
- Keep the logbook flat: A thin, waterproof logbook in a flat case prevents the sheeting from warping.
- Press down over the entire surface: No air gap, no edges, no rounding over a weld seam.
Which magnetic sheeting is suitable for geocaching?
Three points decide:
- Thickness: Thicker sheeting holds better. According to a technical data sheet for ferrite magnetic sheeting, 0.5 mm sheeting is at least 42 g/cm², 1.5 mm at least 66 g/cm², and 2.0 mm at least 103 g/cm². For caches, we recommend at least 0.8 mm, for logbook hiding places rather 1.5 mm or more.
- Anisotropic instead of isotropic: Anisotropic sheeting has a stronger magnetic flux for the same size and thickness. Isotropic sheeting is cheaper, but only holds moderately.
- Surface: With a white or colored backing, the sheeting can be printed on. Raw brown sheeting must be completely covered.
Neodymium magnetic sheeting holds more strongly, but is stiffer and reacts more sensitively to heat. For outdoors, ferrite sheeting is the more robust choice.
When a neodymium magnet clearly wins
As soon as your hiding place has weight, is frequently touched, or is located in a small, uneven spot, there is no alternative to neodymium. This applies to most urban caches:
- Nanos and screw hiding places: Tiny components where there is no room for sheeting.
- PETlings on railings and pipes: Round surfaces on which sheeting never lies flat.
- Magnetic containers and micros: A container with a logbook and pen quickly weighs more than sheeting can securely carry.
- Frequently visited caches: Every finder pulls the cache off and puts it back. A strong magnet locks in cleanly, sheeting slips over time.
The installation method is important. A good neodymium cache has the magnet protected in the housing, glued in, or sealed, so that water does not reach the surface. How this is achieved with the PETling is shown in our post Mounting a PETling magnet weatherproofly. And if you are considering whether a magnet can also serve as a closure, our comparison Screw closure or magnetic closure will help you.
Decision aid for your hiding place
| Your hiding place | Our recommendation | Why |
|---|---|---|
| Nano on screw, nut, or bolt | Neodymium | small construction space, high force required |
| PETling on railing or pipe | Neodymium | round surface, sheeting does not lie flat |
| Magnetic container on electrical box | Neodymium | Weight of container, log, and pen |
| Flat camouflage shield on sheet metal | Magnetic sheeting | thin, printable, inconspicuous |
| Logbook behind traffic sign | Magnetic sheeting from 1.5 mm | flat, large surface |
| Gadget cache with moving parts | Neodymium | precise hold, also as a closure |
| Combo: camouflage surface plus secure hold | both | Sheeting camouflages, neodymium carries |
The combination is, by the way, often the best solution: The sheeting provides the camouflage and a large contact area, an embedded neodymium magnet ensures that nothing slips. Pay attention to the orientation of the poles, so that the magnet and sheeting do not repel each other. How you reliably check the polarity is explained in the post Checking magnetic polarity.
Mounting in five steps
- Test the surface: Hold a magnet against the spot beforehand. Many signs are made of aluminum and are therefore not magnetic.
- Clean the surface: Remove dust, grease, and loose paint residues. Every crumb is a spacer.
- Protect the magnet: Place the neodymium magnet in the housing or glue it in completely. Avoid strong heat during processing, as heat weakens the magnetic force.
- Test run: Remove and reattach the cache ten times. If it slips, the magnet is too weak or the gap is too large.
- Labeling: A note such as "Geocache, please do not remove" prevents misunderstandings with building managers and passersby.
Rules to follow when placing a cache
The Geocaching.com guidelines require, among other things, a distance of at least 161 m from physical stations of other caches. The checklist for cache owners also advises choosing a container only as large as the hiding place can accommodate. In the forest, additional guidelines for protecting flora and fauna apply in Germany, which are summarized in the Geocaching Wiki for Germany. And quite practically: A good cache should not be found randomly as much as possible, but also not in a way that makes it seem dangerous.
Safety with strong magnets
Small neodymium magnets are not toys. According to the Unfallkasse Berlin, swallowing them can be life-threatening, and accidents happen in all age groups. According to the safety instructions from ETH Zurich, if several magnets are swallowed, they can become lodged in the intestine. If you are crafting with children, keep loose magnets out of reach. If a child swallows a magnet, go to the emergency room immediately or call emergency services at 112. Anyone with a pacemaker or defibrillator should consult their cardiologist about how to handle strong magnets.
Our perspective from the cache workshop
We are active geocachers ourselves, and this is exactly the question we ask ourselves with every new hiding place: What does the magnet need to achieve here? Our answer almost always falls on neodymium for urban hiding places. A nano on a screw, a PETling on a railing, or a nut-and-bolt cache on a steel beam must lock securely into place every time it is found and must not slip even after months.
That is why we develop and test our hiding places ourselves for outdoor use. The magnet is protected, the housing matches the surroundings, and you don't have to worry about glue, coating, or polarity. We print many of our parts from PETG, while others are handcrafted from wood.
Magnetic film still has its place with us: as camouflage for flat surfaces and for everyone who likes to craft themselves. In our view, the strongest caches are created when both come together: camouflage that no one notices, and a magnet you can rely on.
Benedikt
Finished magnetic hiding places from CacheWerk
You don't want to tinker for long but want to place a hiding place that holds right away? In our shop you will find magnetic hiding places developed by geocachers for geocachers: the stainless steel magnetic nut-and-bolt cache, waterproof and almost indistinguishable from a real nut as an urban nano, and the screw hiding place with secret compartment and magnet in a two-pack.
For railings, pipes, and signs, we have our PETling with magnetic holder in camouflage and signal colors. You will find logbooks, spare parts, and other accessories in our Geocaching Equipment and Accessories category.
Frequently Asked Questions
What does neodymium mean in a magnet?
Neodymium is a rare earth metal. Together with iron and boron, it forms the NdFeB alloy, from which the strongest permanent magnets are made. This is why a neodymium magnet holds many times stronger than a ferrite magnet of the same size.
Does magnetic film stick to all metal?
No. Magnetic film only sticks to ferromagnetic surfaces such as sheet steel or iron. It does not stick to aluminum, copper, many types of stainless steel, and of course not to wood or plastic. Always test the spot with a magnet beforehand.
Is aluminum foil magnetic?
No, aluminum is not magnetic. A magnet sticks neither to aluminum foil nor to aluminum signs, and aluminum foil under a cache does not shield the adhesion. Many traffic signs are made of aluminum, so check beforehand whether your desired hiding place is magnetic at all.
Which glue holds on neodymium magnets?
For outdoor use, two-component epoxy glue works well because it completely encloses the magnet and protects it from moisture. Hot glue is less suitable because heat can weaken the magnetic force and the adhesive joint becomes soft in the sun. Roughen the adhesive surface slightly without damaging the magnet's coating.
Do magnets affect the body?
Not in normal geocaching use. It becomes dangerous if children swallow small magnets, because several magnets can attract each other in the intestine. If you have an implant such as a pacemaker, keep strong magnets at a distance and ask your doctor.
Sources
- Beloh: Magnetic film, applications and handling instructions
- MEGALAB: Magnetic adhesive films
- Wikipedia: Neodymium-iron-boron
- Haas Magnettechnik: Neodymium magnetic films and tapes
- Magnetic tape data sheet
- Technical properties of magnetic films (PDF)
- Flyeralarm: Application instructions for magnetic film (PDF)
- Geocaching.com: Hiding guidelines
- Geocaching.com: Checklist for cache owners
- Geocaching.com Wiki: Regulations in Germany
- geocaching-info.de: Hiding
- Unfallkasse Berlin: Caution with magnets
- ETH Zurich: Safety instructions for neodymium magnets (PDF)