Magnetic Slime

This little project feels like something out of a sci-fi, which perhaps is why I love it so much. Add some magnetite powder to your next batch of slime, get a strong rare earth magnet, and your kids (or you) will have a blast making zombie worms and magnet eating monsters- straight out of the movies!

Safety: Do not ingest any part of this project. Do not use any of the materials around small children or children who put things in their mouth. Too much iron is poisonous and it should not be ingested in this form. Rare earth magnets are very strong and can pinch fingers, be careful when using them. Magnets should never be left around small children who could ingest them. Do not use magnets near electronics or credit cards. The magnet in the video has a pulling force of 48 lbs. This was more than sufficient. If you are doing this with kids, do not use a more powerful magnet and only use one magnet at a time to avoid pinched fingers.

Materials

Procedure

  1. In a bowl or cup, dissolve the 1/8 tsp borax in 1/4 cup hot water. Set aside.
  2. To a different bowl, add 1/4 cup glue, 1/4 cup water, and 3 tbs iron oxide powder. Mix well. (Note: The powder will stain skin, so try not touch the iron oxide with your hands at this point, wait until the borax solution is mixed it. If you do get it on your hands, dish soap washes most of it off.)
  3. Slowly add the borax solution to the glue mixture and mix well.
  4. Take the slime out and knead with your hands till it is smooth. If it feels sticky, dip it in the extra liquid in the bowl and knead again.
  5. Start playing with the slime and magnet!

The Science Behind Slime

The glue contains a long molecule called polyvinyl alcohol (PVA). It is a polymer, which is a molecule that contains repeats of a subunit molecule (for example, “A” is a subunit and “AAAAAAAAAAAAAAA” is a polymer of A). Borax (sodium tetraborate) is a small molecule that can stick to parts of the PVA through hydrogen bonds. This means one side of the borate molecule can stick to one strand of PVA, while the other side of the borate can also stick to a different strand of PVA, creating a bridge between the two PVA strands. This is called crosslinking.

Having many crosslinking sites usually makes a polymer more rigid, but the interesting thing about borate/PVA crosslinking is that the bond is transient, meaning it can easily break and reform somewhere else. This causes the slime to act kind of like a liquid and kind of like a solid. If given time, the PVA can ‘flow’ as gravity pulls and breaks the borate/PVA crosslinks. It acts like a slime instead of a true liquid because as the PVA molecules pass by more borate, they can momentarily bond to borate and another strand of PVA, slowing down the flow. If you pull the slime fast, you break all those bonds quickly, allowing the slime to act like a solid momentarily.

The Science Behind Magnetic Slime

The iron oxide powder in the link above is magnetite, which is a natural mineral made of iron and oxygen. Like many iron-containing compounds, it is attracted to a magnet.

The iron oxide particles in the powder will become suspended in your slime matrix. As the particles are attracted to the magnet, they will pull the slime matrix with them, causing a whole section of the slime to move with it. This makes for some really cool effects!


If you’re looking for a project to use some of the leftover ion oxide powder, try our DIY Magnetic Shapes!

Diaper Snow: Sensory Science

Deep inside diapers lies an amazing molecule that can absorb hundreds of times its weight in water. It is called sodium polyacrylate and is an inert, skin-safe polymer that can provide loads of fun sensory play. Read on to learn what it is, where to get it, and what to do with it!

Materials and Methods

Sodium polyacrylate can be purchased as artificial snow (click here for to buy) or harvested from an unused diaper. To do the latter:

  1. Cut the top cloth-like layer of the diaper (the part that touches the baby) right down the middle width-wise.
  2. Fold it on the cut, cut side down and put it in a plastic tub.
  3. Shake it until tiny white specks gather at the bottom of the container.
  4. Remove the diaper.
  5. Add water (with food coloring if you want) a little at a time and watch as the water is quickly absorbed into the growing mass.
  6. For a lighter texture, add less water, for a slushy texture add more water.

Discussion

Polyacrylate, on the molecular level, is like a long string of negative charges. The sodium, which is positively charged, sits on these negative charges all along the string, which allows the polymer to coil and tangle up. When water is added, it displaces the sodium and nuzzles up with the negative charges. This causes the polymer strand to unravel, not only increasing the size of the gel, but also exposing more negatively charged sites so even more water can bind. This is why you get so much absorbent bang for your buck.

What to do with it?

  • Sensory Bins
    • Add cups and molds and make sand castle-like creations with the slush form (more water)
    • Add small world toys, like evergreen trees and arctic animals, to play with the lighter form (less water)
    • Initially make the snow without coloring, then give the kids squirt bottles with colored water to
  • Magic Tricks
    • Make water “disappear.” Put the dried sodium polyacrylate at the bottom of an opaque cup, show that it is “empty”, pour water in, then flip the glass upside down. The polymer should absorb the water, expand, and stay inside the cup, making it look like the water disappeared.
  • Fake Snow
    • You can inexpensively buy enough sodium polyacrylate that you can fill a kiddie pool (or larger!) sized area with fake snow that kids can play in for a Frozen themed party or what-not.
  • Fluffy Slime
    • Add it to your favorite slime recipe for a whole new feel

The Best Black Slime Recipe Ever

For the most perfect black slime recipe ever, look no further! Say goodbye to grit and residue with this amazing deep dark goop!

Materials

This includes affiliate links. If you purchase from the links below, I will receive a small commission at no extra cost to you.

Procedure

  1. In one bowl, dissolve 1/2 tsp of borax into 1/2 cup of hot water.
  2. In the other bowl, mix 1/4 cup of glue with 1/4 cup water.
  3. A tsp at a time, mix 4-6 tsp of activated charcoal into the glue/water mixture. It won’t mix in at first, but just keep stirring, it will eventually mix in! Just a minute or so of stirring. Stop adding when it’s black enough for you. Mix until thoroughly combined.
  4. Add 12 tsp borax solution to the glue mixture a teaspoon at a time while stirring. This slow addition of the borax ensures a super smooth slime without the need for lots of kneading. You will know when to stop adding when all of the black glue mixture is in the ball of slime and there is none left in a puddle at the bottom of the bowl.
  5. Pick up the glob and fold and squish a few times. You’re done! After you’re finished playing with it, store it in an air tight container. If it feels gooey after a few days, add a little more borax solution till you get the consistency you like. We think this gradual goo-ing might be due to the activated charcoal absorbing some of the borax (see below for what borax does!).

Discussion

The glue contains a long molecule called polyvinyl alcohol (PVA). It is a polymer, which is a molecule that contains repeats of a subunit molecule (for example, “A” is a subunit and “AAAAAAAAAAAAAAA” is a polymer of A). Borax (sodium tetraborate) is a small molecule that can stick to parts of the PVA through hydrogen bonds. One side of the borate molecule can stick to one strand of PVA, while the other side of the borate can also stick to a different strand of PVA, creating a bridge between the two PVA strands. This is called crosslinking.

Having many crosslinking sites usually makes a polymer more rigid, but the interesting thing about borate/PVA crosslinking is that the bond is transient, meaning it can easily break and reform somewhere else. This causes the slime to act kind of like a liquid and kind of like a solid. If given time, the PVA can ‘flow’ as gravity pulls and breaks the borate/PVA crosslinks. It acts like a slime instead of a true liquid because as the PVA molecules pass by more borate, they can momentarily bond to borate and another strand of PVA, slowing down the flow. If you pull the slime fast, you break all those bonds quickly, allowing the slime to act like a solid momentarily.

This dark black slime is perfect for Halloween. Throw some googly eyes, plastic spiders, or confetti in there for hours of fun!