UPDATE 3/14/17: Good gravy! I had no idea slime was so popular! I have been getting some messages about Borax safety and kids getting sick after playing with their slime for a few days. As long as you are not eating the slime or rubbing it in your eyes the Borax should not be a problem. What is a problem is not storing the slime in a sealed bag in the fridge. If your slime hangs out in your kid’s book bag and they have been playing with it with less than clean hands there is a very good chance that bacteria and/or mold will find that slime is an ideal place to take root. Please make sure to keep the slime in a sealed bag in the refrigerator when your kid is not playing with it. It is also a good idea to toss the slime in the trash and make a new batch after about a couple days. There are a lot of germs floating around – let’s not give them a place to grow!
UPDATE 3/9/17: There are some “new” slime recipes floating around that use saline solution for contact lenses like this. These drops contain sodium borate, also known as Borax. So while it looks like a new recipe, it is really just the same glue and Borax recipe found here. You can use the saline solution instead of Borax and water if you like, the results are the same.
UPDATE 12/30/15: Check out the video of Edible Slime (recipe below) made with Go Ask Mom!
Kids love it. Parents hate it. Halloween is the time we all hear about it.
Sticky, ooey, gooey, messy slime!
I would like to present the grossest, definitive recipe collection of slime recipes, based on years of experience making, playing with and teaching with slime.
First, the science:
What makes slimes slimy?
All slimes are non-Newtonian Fluids, which is just a fancy way of saying they don’t act like most fluids or liquids are supposed to act. Isaac Newton (the same guy who made the force laws) came up with a way to describe how liquids flow, called viscosity. Thin liquids like water or vinegar have a very low viscosity and thicker liquids like molasses or ketchup have a high viscosity. Keep in mind that viscosity is not the same as density. For example, vegetable oil is more viscous than water but floats on top of water and is less dense.
Newton also observed that viscosity is affected by temperature. Heating a liquid makes it less viscous and cooling it down makes it more viscous. That is why some folks say “slower than molasses in January.” These liquids are Newtonian. A liquid is non-Newtonian when its viscosity can be changed by other factors such as stirring, stretching or squeezing.
There are two types of non-Newtonian fluids:
- Shear thinning where stirring, stretching and squeezing makes the liquid less viscous and flow easier. For example, ketchup, a non-newtonian fluid, will flow out of a bottle easier if you whack the bottom of the bottle or stir it with a knife. Other examples are mayonnaise, honey, mustard and glue.
- Shear thickening where stirring, stretching and squeezing makes the liquid more viscous and flow slower. The classic example is quicksand. The more you struggle and kick around in quicksand, the tighter it holds on to you. All of the slimes below are shear thickening slimes. That is, the more vigorously you play with them the harder they become. But if you push, twist and pull slowly they will act more like a liquid.The slimes below are shear thickening non-Newtonian fluids.
For more information on applications of Non-Newtonian fluids check out The Science of Slime by Brian Rohrig.
What are slimes made of?
Most slimes are made of polymers – chains of molecules, like a long chain of paperclips. Slime happens when you add a cross linking chemical that connects those chains, like strings attached to different paperclip chains and tangling them up together so they can’t be easily pulled apart.
All of the recipes here consist of a polymer and a cross linker.
There are only four basic slime recipes. All recipes you might find online or elsewhere are just variations of these four.
This is your simple basic slime named after the Dr. Seuss book. Here the polymer is cornstarch and the cross linker is water.
Start with 1 cup of cornstarch in a bowl and slowly mix in water until your slime is a consistency you like. If it gets too runny just add more corn starch.
BONUS: Electroreactive Oobleck
Replace the water with vegetable oil and create a liquid that is the viscosity of a thin gravy. Charge up a balloon or Styrofoam cup by rubbing it on your hair (or your kid’s hair, or the dogs hair). While pouring the oobleck with oil into another cup, hold the charged up object near the stream and watch the viscosity suddenly change to a near solid – the flow will stop!
If you are comfortable with Oobleck give this classic slime a try. Here the polymer is glue and the cross linker is Borax soap dissolved in water. For an opaque slime, use white school glue. For a clear slime, try clear gel glue.
½ cup of glue (or one 4 ounce bottle
½ cup of water
Cross link solution:
1 cup warm water
1 teaspoon of Borax soap
Mix each solutions in two separate bowls. Add the cross link (Borax) mixture to the polymer (glue mixture) and mix slowly with a spoon. Once the slime thickens (this means the cross linker is binding up those polymers!) you may want to use your hands to knead it together. Feel free to experiment with different amounts of polymer (glue) and cross link (Borax) solutions.
Classic Slime Variation
This version of the classic slime recipe uses liquid starch as a cross linker instead of Borax. It is a little bit simpler to make since you don’t need water. Just mix equal parts glue and liquid starch. If you want a clear(ish) slime, use clear glue instead of white glue.
This version of slime is edible – although it doesn’t taste good so I wouldn’t recommend eating it. However if you are making slime with young kids and don’t want to worry about them eating something they shouldn’t, this is the way to go.
Add 1 teaspoon of soluble fiber, like Metamucil, just make sure the main ingredient is Psyllium, to 1 cup of water in a large bowl.
Stir well and then heat in the microwave until it boils. This could take 1 to 4 minutes depending on your microwave oven. Stir and then microwave for another 2 minutes – repeat this 4-5 more times. Let the slime cool completely before playing with it.
There are numerous additives you can use to make your slime magnetic, glow in the dark, and more. Note that you need to add these to one of the liquids in your slime BEFORE mixing or else you will have a heck of a time getting it all in there. Try out these suggestions.
- Food coloring – Try light green for ectoplasm or dark red for blood.
- Baking soda – gives the slime a lighter, foamier feel
- Sand – add play sand to your slime and make oozing sand castles
- Iron oxide powder – make your slime magnetic
- Glitter – add glitter to colored slime for a jeweled look or to white slime for a sparkling snow effect.
- Confetti shapes – this works best with clear slime. Confetti is basically larger glitter. You can also add small plastic toys and beads to add a sensory component.
- Polystyrene beads – add slightly more beads than you have slime (the classic recipe works best here) to create moldable floam.
- Thermochromic pigment – make color changing “mood slime”. You can order the pigment from Amazon.
- Tonic water – make your slime glow under a black light. Simply replace the water in Oobleck or classic slime with tonic water.
- Glow in the dark paint or neon food coloring – find your slime when the lights go out! You can also soak the felt ink tube from a highlighter in hot water overnight to pull out the ink and use this to make glow in the dark slime.
Slime Making Tips
Want to reduce the mess factor? Put your ingredients in a sealed plastic bag to mix. Once the polymer and crosslinker are well combined, the slime won’t be quite as slimy and sticky.
When you are done playing, put the slime in a sealed plastic bag and store in the refrigerator. This will reduce the chance of mold. Get rid of the slime after a couple of days.
Only Oobleck and the edible slime should be disposed of down the sink. The other slimes need to go in the garbage can.
Science Fair Ideas
Measure the viscosity of different slimes by timing how long it takes equal volumes (say ½ cup) to flow through a funnel. More viscous slimes will take longer than less viscous slimes.
Test the shear-thinning properties of ketchup or mayonnaise. Measure its viscosity after it has been sitting for a couple of hours in the funnel and then measure it again after stirring for different amounts of time (5 seconds, 10 seconds, 20 seconds…) Does stir time affect viscosity?
Choose a slime recipe and adjust the amount of polymer and cross linker. How does this affect the viscosity and other slimy properties?