Iron filings suspended in a viscous liquid inside a clear bottle align along the magnetic field lines when exposed to a strong magnet, creating a visible three-dimensional representation of the field.

1. Add a few tablespoons of iron filings into a clear, sealable bottle.
2. Fill the bottle with a viscous liquid (such as mineral oil, baby oil, corn syrup, or glycerin) until the filings are suspended and move freely.
3. Seal the bottle tightly to prevent leaks.
4. Hold the bottle up to a light source.
5. Place a strong magnet against the side of the bottle and observe how the filings align along the magnetic field lines.
6. Experiment with different magnet shapes (bar, horseshoe, etc.) and with multiple magnets to see how the patterns change.

3D Magnetic Field demonstration - Jade Nowlin:

Magnetic Field lines, 3D - Jon Jasinki (using commercially available apparatus):

📄 3D Magnetic Field Viewer - botronics (Instructables): https://www.instructables.com/3D-Magnetic-Field-Viewer/

• Use different liquids (varying viscosity) to see how quickly the filings move into position.
• Try varying amounts of filings to observe differences in field visibility.
• Place two magnets in attraction and repulsion to compare the field interactions.
• Use colored light or backlighting to enhance the 3D visibility of the field lines.

• Handle neodymium magnets carefully—they can pinch fingers or shatter if allowed to snap together.
• Keep strong magnets away from electronics, credit cards, and pacemakers.
• Avoid inhaling or ingesting iron filings; wear gloves when handling them.
• Ensure the bottle is sealed tightly to prevent spills or leaks.

• Why do the iron filings align themselves in the presence of a magnetic field?
• How does the shape of the magnet affect the pattern of field lines?
• What happens when two magnets are placed near each other—both attracting and repelling?
• Why is a viscous liquid necessary instead of just air or water?
• How does this demonstration help visualize the otherwise invisible magnetic field?