How to Make Magnetic Slime

Did you know that it’s possible to make slime magnetic?  I didn’t either until recently when I found a post on Pinterest from Instructables about making magnetic silly putty.  I really recommend this slime recipe rather than silly putty – more on that in a minute.  But first, check out what magnetic slime can do!

Magnetic Slime

Magnetic slime is really fun to play with on its own.  It stretches and squishes.  If you hold it up, it oozes down to the floor in a long strand!  Adding the element of magnet play makes it even more awesome.  This is a great project to put on your to-do list for a rainy day, spring break, or summer!  It would also make a great group activity for a science club or scouting group.

Magnetic SlimeThere’s just something about watching a liquid move without touching it…  So fascinating!

To make your own magnetic slime, you will need:

(These links are Amazon affiliate links, meaning that if you purchase through the links, I will earn a small percentage of the sale at no extra cost to you.  This is one craft that I would recommend ordering from Amazon because the items can be hard to find.)

Magnetic Slime

Here’s how to make magnetic slime:

Step 1:  Pour 1/4 cup of liquid starch into a bowl.  Add 2 Tablespoons of iron powder and stir until well mixed.

Magnetic Slime

Step 2:  Add 1/4 cup white school glue and mix.  It will look like a huge mess that isn’t going to turn into anything, but keep stirring!

Magnetic Slime

Step 3:  Take the slime out of the bowl and mix with your hands.  Squish and squish until it’s well mixed.   There will be some liquid left in the bowl that isn’t part of the slime, and that’s fine.  Your hands will get very black, and you should wash it off right away.  We had black left around our fingernails and slight staining on our hands, but it was mostly gone by the next day.

If you’re not a fan of lingering black around your fingernails, disposable gloves would solve that problem.

Magnetic Slime

Step 4:  Pat the slime dry with a paper towel to get rid of any excess liquid.  The finished slime won’t make your hands black, but the extra liquid will.  Once the slime is “dry,” it’s ready to play with!

Magnetic Slime

We made our slime as a play date with friends who also have four boys.  So much fun!  Everyone enjoyed it – ages 5 to 12!  We mixed up the slime with 2 kids at a time to minimize the mess.  I put down a large piece of parchment paper to protect the counter, but we didn’t have any trouble wiping up slime spills that did get on the counter.  No stains, but ours aren’t white.  If you have very light counter tops you might want to cover them just in case.

One of our friends figured out that he could blow a bubble with the slime – it really is amazing stuff!

Magnetic Slime

Here are a couple more important notes:

  • Neodymium magnets are extremely strong!  Fingers can easily get pinched when trying to separate the magnets, so we didn’t even separate ours.  (Plus, they’re small, and the whole stack of them was easier for the younger boys to hang on to.)  Be sure to keep the magnets away from cell phones, computer, and other electronics!  Also make sure that no one puts them in their mouth – these would be very dangerous if swallowed.  Overall, this is not a project for kids who still put things in their mouths.
  • Iron oxide powder is not good to breathe.  This is why we mixed our iron in with the liquid starch.  In the post on Instructables, they recommend mixing the iron powder directly into ready-made silly putty.  Aidan and I tried doing that the day before our friends came over, except that we used our homemade silly putty recipe.  Working with the iron powder was way more messy than just stirring it into a liquid, and we had a LOT of trouble getting it to mix with the silly putty. I would go the slime route instead of using silly putty, especially for younger kids.

If making magnetic slime seems like too much of a hassle, you can actually purchase magnetic silly putty –  Crazy Aaron’s Thinking Putty which comes with a magnet and does the same thing.  (Although judging by the reviews, I think the homemade slime responds better to the magnet!)

Also, here is our colored slime recipe – without the iron.  It’s really fun this way too, and better for younger kids! 


    • Amber says

      I think this is such a wonderful site!!! Being a mom of two boys, I happened upon this site when they’re crying in despair because they are so bored. We had made the liquid starch ourselves because I didn’t have any. Because we *really* wanted to make this amazing goo and didn’t have any ferrous powdered metals around (that I knew of), I decided it might be kind of cool to make our own. Go science! So for others who happen by this site – a good substitute for the ferrous oxide would be laser printer powder (if you have it handy). Otherwise, I highly recommend you order it online because making it yourself (especially with kids around) is either extremely dangerous or takes forever.

    • SarahDees says

      The slime should last for at least a few weeks, and probably longer than that. I think that weather conditions in your area probably affect how long it lasts. We are storing ours in ziploc bags.

      • Renae says

        I know this is an old comment but I’m a children’s librarian and we always try to send slime home in old babyfood jars. The lids are tight and keep it nice and fresh for over a month!

  1. Nancy says

    Please be aware that magnets of this strength can cause havoc and even death if swallowed. It would be best to leave them stacked and then wrap them with electrical or duct tape to avoid the temptation to play with them individually. Otherwise, a very interesting activity.

    I also notice that the iron oxide powder on Amazon comes in red, as well. Is there any functional difference in the two?

    • SarahDees says

      I wondered the same thing about the colors! I’m not sure what the answer to that is. I ordered the black because that’s what reviewers on Amazon were recommending for magnetic silly putty.

    • Amber says

      Sorry to be nerdling on this issue. There is no major difference other than the compound structure. Each should work as well as the other. The difference in color is caused by the difference in oxidization, really. I think it’s also heated and the black may be a bit more prone to magnets. Don’t quote me on that. But both have Fe and it’s simply (again, I think) an extra oxygen molecule on one than the other (or was that less.)

  2. ana says

    This would be very poisonous, wouldn’t it? I remember reading somewhere about letting little kids play with iron shavings and magnets, that they can be poisoned by very small amounts. No doubt this is too disgusting to eat on purpose but what about little ones getting it in their mouths by accident?

    • SarahDees says

      I looked up the material safety data sheet for black iron oxide, and it is listed as non-toxic. The main risk is irritation from inhaling it, but with the way it is used in this activity, that should not be a major problem. Sensitive individuals could always wear a mask. The msds says to seek medical attention for ingesting large quantities. With proper supervision, I don’t know why anyone would ingest any quantity of this! It’s definitely not for kids who still put things in their mouths! I hope that answers your question. This is a science project, and proper precautions should be taken as such.

  3. Jen says

    I’m a chemistry professor and I’ve done this experiment many times in K-12 classrooms, summer camps, etc. It is super fun and teaches about both polymers and magnets. My recipe uses 20 Mule Team Borax and water rather than Sta-Flo (its the sodium tetraborate in both that cross-links with the PVA in the glue to make slime). As far as the safety goes, many iron oxides such as this one are used in tattoo inks (Fe3O4 and FeO in black, and Fe2O3/rust in red). The biggest concern would be ingesting and breathing it in large quantities. I always spoon it out myself into the kids’ baggies full of glue which also curbs the mess. Once the powder is incorporated into the slime, it stays there. I’ve made it with my three year old and he plays with it all the time. One bag is nearly a year old and is still good, although I sometimes need to add a bit of water.

    • SarahDees says


      Thank you so much for chiming in! Our experience was definitely that the powder stays in the slime once mixed in, so thank you for confirming that.

      Do you mix it up in a baggie? That would be a great way to contain the mess and not do as much mixing with your hands!

    • Heather says

      Hello Jen, Thanks for the information. How much Borax and Water should I use? I already have it on hand, so I am curious.

      • Kristen says

        I’ve made it many times… I use a teaspoon of borax in a 1/2 cup of hot water. Sometimes the borax doesn’t dissolve completely, and it still works perfectly. I use 2 4 oz bottles of Elmer’s glue then 2 bottles full of hot water and mix that along with food coloring before I mix in the borax solution. Hope that helps!

  4. Shelly Smith says

    We made some yesterday and my boys are loving it!! I was wondering if anyone has other uses for the iron oxide, as we have so much “leftover” and would like to put it to good use! Any ideas??

    • Kate says

      Shelly– Christmas presents! Either premixed, and labeled with a set of magnets on the side, or a baggie of it along with a list of the other ingredients needed (since it is the hardest one to find!) It could be a frugal gift for little friends! :)

  5. dominique says

    We are trying this idea out for our school’s science fair, and ended up with pretty solid slime…..any suggestions?

  6. D sprague says

    Why is this being marketed for boys? I know a lot of young girls who would and should enjoy this stuff.

  7. Ruby says

    Love this! But why is it just for boys? I would have loved this stuff when I was a little girl. Just putting it out there :-)

    • SarahDees says

      This is definitely not just for boys! The name of my site is Frugal Fun for Boys because I have four boys. As a mom of boys, I know that it’s harder to find crafts and activities that boys will go for, so this site is designed to be a resource for moms of boys. However, that doesn’t mean that girls wouldn’t enjoy many of these activities!

  8. Brandi says

    My boys are spiderman fans and this reminded me of the black alien goo that takes over spiderman I’m deffinally gonna make for b-day party.

  9. Kari says

    Thank you for writing these instructions and verifying the method. We made half batches successfully. Thank you for the link to the iron powder. Gratefully, Kari in Texas

  10. shannon morales says

    I did not have any liquid starch, so I tried making my own with water and cornstarch. Total fail!!!! Looking forward to buying some liquid starch and trying again.

  11. Robin Finch says

    Anyone know where you can get iron oxide in Canada? Amazon won’t ship it from the US and does not have it. Any idea what other stores might carry it? (magnets as well)

    • Joe says

      Iron oxide is easy to make with a piece of iron, some DC current and a container of water. Attach the iron to the positive wire and stick it in the water, add a tiny bit of salt for conductivity, put the negative opposite the positive in the water and turn on the power. I used to use a train transformer because it could vary the amount of current. Once the electric starts flowing you will see bubbles released from the iron, this is the oxidation happening, Wikipedia is your friend when doing stuff like this. Extra iron oxide can be mixed 50/50 with powdered aluminum to make a whole other science project, thermite, which is way fun but very very dangerous. When it burns, it burns at 5000 degrees. It can be used like the railroad companies use it to weld train tracks together, or it could be used to melt a hole through the engine block of a car, ya know whatever, very versatile

  12. says

    You are surely the coolest mom ever!! Thanks for sharing such an incredibly cool activity!

    This would be an awesome activity to prepare for a trip to Canada to see Magnetic Hill where things appear to roll UPHILL!!

    Love your stuff. I will link this to a post on Canada. Would love a shout out from you!

    Thanks for sharing,
    Natalie, The Educational Tourist

  13. Misty says

    I can’t seem to get ours to not leave black smudges everywhere and we’ve tried “drying” it, but it sticks to the paper towels. What should I do?

  14. kate says

    I am hoping to do this with the entire 5th grade at my son’s school. (approx 75 kids) Did you use the 10 magnets per child? Did your foursome split the magnet? How would you suggest I do it for such a large group? I like the baggie idea the chemist previously suggested.

    • Sarah says

      We used all 10 magnets as one unit – the kids just passed it around. For 75 kids, especially since they are 5th grade and won’t be putting the magnets in their mouths, I think you could probably do a chunk of 3 magnets stuck together. Maybe plan to share the magnets among groups of 4 students? You definitely don’t need a magnet for each child. The slime is fun enough on its own while they wait for a turn with the magnet. But if you do single magnets, they are harder to hold onto and would be easier to lose. That’s why I’m thinking chunks of 3 stuck together. Just my opinion – not sure if that helps or not!

    • Sarah says

      The iron powder is used in making black paint, and it has an overpowering black color. I don’t think it would be possible to color it any other color.

  15. Rebel says

    I’m excited! We are making this today with our little homeschooled group. I’ve done slime with the borax before, but the starch was so cheap at Walmart (near the fabric softener) that I figured we could do it both ways if one doesn’t work well.
    Thank you for posting this. If we have any suggestions afterward, we’ll let you know. (I like the Baggie idea).
    Magnets are so strong…once your able to remove one, it’s got to be kept far from the others. I let the magnets get too close and they snapped together so fast that the corner broke. Oops. Be safe.

  16. Jan W. says

    OK, what did I do wrong? Made this today and it was a stringy mess! We mixed the iron oxide really well with the starch before we added the glue. Used Elmers White Glue, then patted it a lot with paper towels. Still kept getting black on our hands. We were really disappointed that it didn’t work.

    • Sarah says

      You were so close! If you have enough materials, try it again! If it’s stringy and a sticky mess, add a little more starch and keep mixing. An easy way to do this is to dip the whole blob in some starch, then keep kneading it. Try washing your hands well, then squeezing some more. Once you have enough starch and it’s well mixed it will stop being stringy. I hope this helps – let me know!

  17. Ken says

    I would think that iron filings would not work as well as iron powder due to the size of particles. The filings wouldn’t mix in with the polymer as well and may end up with jagged/sharp part protruding.

    People looking for something to do with excess iron powder…try to make your own hot hands hand warmers. Iron powder, water, and salt are the 3 main ingredients in most hand warmers. The reaction of iron and oxygen creating rust is exothermic and will produce heat. Simply put the iron in a cup or bag, add a pinch of salt and an eyedropper or 2 of water. It should heat up fairly quickly but not so much that it will burn anything.

    Still, as mentioned earlier the fine powder is harmful if inhaled so use caution with children!

    • Sarah says

      Yes, I agree – iron filings will not work. I’m so curious to try the hand warmer project! Thanks for the suggestion!

  18. Megan Scully says

    Hi! How many students would be able to make the slime with the above amounts? I’m doing this with a class of 10 students. Thanks!

    • Sarah says

      It only takes a few minutes to mix up, but I think that the time needed would also depend on the age of the students, how many students you have, how many adults are helping, and what your classroom set-up is like. Lots of factors!

  19. Chloe says

    Im just a kid.We have a science fair coming up and my friends and I are gonna use this!We think it’s really cool!! The only thing we’re stuck on is that we dont have any STRONG

    • Sarah says

      I think you’ll really find it worth it to order some neodymium magnets. They’re the only kind that really work!


  1. […] This has been on our “To Do” list for this year but we haven’t ordered the ingredients yet. Frugal Fun for Boys did though and you can see how cool this looks on their site! […]

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