Table of Contents
Okay, everyone has played with slime or silly putty before. You stretch it, you squish it, you bounce it. It is incredibly fun, but it is just a dumb lump of stretchy plastic.
But what if you could make that putty come alive?
Imagine taking a normal, stretchy black blob of slime and placing it on a table. Then, you place a shiny, silver cube magnet right next to it.
The slime doesn’t just sit there. It actually reaches out. The black slime slowly stretches its “arms” toward the magnet, creeping across the table like a horror movie monster. When it touches the magnet, the slime begins to climb up the sides of the cube, pulling itself upward until it completely swallows the magnet alive, pulling it deep into its dark, squishy center.
This isn’t a sci-fi movie. This is Magnetic Slime. It looks like a living alien lifeform, but it is actually a beautiful demonstration of how invisible magnetic fields can force materials to physically move. Let me explain how you can bring putty to life.
The Secret Ingredient
Normal slime is basically just a type of flexible plastic (a polymer). It is incredibly stretchy, but it doesn’t care about magnets at all. If you put a magnet near normal slime, absolutely nothing happens.
To bring the slime to life, we have to inject it with metal. Specifically, we have to mix the slime with a very fine, completely black metal powder called Iron Oxide.
Iron Oxide is highly magnetic. (It is actually the exact same black powder used to make the back of old cassette tapes and floppy disks work!) When you fold and knead this black iron powder into the gooey slime, the slime becomes packed with millions of microscopic, invisible metal magnets.
If you want to read the hardcore physics of how iron atoms interact with magnetic fields, the American Physical Society (APS) has some amazing articles on ferromagnetism.
The Alien Attack
So, you have a blob of black, iron-infused slime. Why does it physically move and swallow things?
It all comes down to invisible magnetic lines of force.
When you place a super strong magnet next to the slime, the magnet shoots out an invisible web of magnetic pulling-power. This invisible web grabs onto the millions of microscopic iron pieces trapped inside the slime.
The magnet violently pulls the iron pieces toward it. Because the iron pieces are trapped inside the sticky, gooey slime, they end up dragging the entire blob of slime along with them! It looks exactly like the slime is crawling on its own, but really, the magnet is just reeling it in like a fish on a hook.
Because the slime is so stretchy, it doesn’t just bump into the magnet; it continues to be pulled by the magnetic field from all sides. The slime physically wraps itself around the magnet, creeping up the sides and over the top until the magnet is completely swallowed and hidden inside the blob. You can read more about how magnetic flux lines manipulate soft materials over at the Institute of Physics (IOP).
Getting the Right Magnet
Here is the catch: a weak, boring refrigerator magnet will not work for this trick. A cheap magnet doesn’t have a strong enough invisible web to physically drag heavy slime across the table.
To make the slime crawl, you absolutely must use a Super Strong Neodymium Magnet. Neodymium magnets are incredibly powerful rare-earth magnets that can pull heavy objects from several inches away.
And if you don’t want to mess around with trying to make the slime from scratch using glue and liquid starch, you can easily just grab a pre-made tin of Ferromagnetic Thinking Putty which already has the iron oxide perfectly mixed in!
To read the official safety rules regarding how dangerous swallowing rare-earth magnets can be for kids, check out the guidelines at the Centers for Disease Control and Prevention (CDC).
Quick Magnetic Slime Summary
What you need:
– Liquid school glue (Elmer’s works great)
– Liquid starch
– Iron Oxide powder (Black iron powder)
– A disposable mixing bowl and spoon
– A super strong Neodymium magnet
Step-by-step guide:
1. Pour about 1/4 cup of liquid glue into your mixing bowl.
2. Add two big spoonfuls of the black Iron Oxide powder into the glue. Stir it until the glue is completely pitch black.
3. Slowly pour in the liquid starch while stirring constantly. The glue will start to clump up and turn into stretchy slime!
4. Take the slime out and knead it with your hands until it isn’t sticky anymore.
5. Place the black slime on the table and set your Neodymium magnet about an inch away.
6. Watch the slime physically reach out, crawl across the table, and swallow the magnet alive!
10 Magnetic Brain Teasers
Think your brain has a strong pull? Try to answer these 10 attractive riddles!
1. The Riddle: I am the pitch-black metal powder you must mix into the slime to give it its magnetic superpower. What am I?
The Answer: Iron Oxide.
2. The Riddle: I am the invisible web of pulling-power that shoots out of the magnet and grabs the iron in the slime. What am I?
The Answer: A magnetic field.
3. The Riddle: I am the specific type of incredibly strong, rare-earth magnet you absolutely must use to make the trick work. What am I?
The Answer: A Neodymium magnet.
4. The Riddle: Because the iron is trapped inside this sticky, stretchy substance, the iron drags the whole blob with it. What is the substance?
The Answer: Slime (or putty).
5. The Riddle: When the slime finally touches the magnet, it doesn’t just stop; it does this until the magnet is hidden. What does it do?
The Answer: Swallows it (or wraps around it).
6. The Riddle: I am the common white school supply you mix with liquid starch to create the actual bouncy putty. What am I?
The Answer: Glue.
7. The Riddle: Because you don’t want to permanently ruin your mom’s good dishes with black iron dust, you should mix this in a bowl that is… what?
The Answer: Disposable.
8. The Riddle: I am the government agency that warns parents about the severe dangers of accidentally swallowing neodymium magnets. What am I?
The Answer: The CDC.
9. The Riddle: I am the old, retro music technology that actually used this exact same black magnetic powder to record songs. What am I?
The Answer: Cassette tapes.
10. The Riddle: I am the fancy science term for materials that are highly attracted to magnets, just like iron. What am I?
The Answer: Ferromagnetic.
The Wrap Up
Magnetic Slime is the closest thing you will ever get to owning a pet alien.
By trapping millions of microscopic pieces of iron inside a stretchy polymer, you get to actually see what an invisible magnetic field looks like in real time. The magnet reels the iron in, and the slime just goes along for the creepy ride. If you want to dive deeper into how engineers use “ferrofluids” to build advanced robots, bookmark the National Science Foundation (NSF). Keep your magnets close, and your slime closer!
Cited Sources & Evidence
- American Physical Society (APS)
- Institute of Physics (IOP)
- Centers for Disease Control and Prevention (CDC)
- National Science Foundation (NSF)