Traditional oobleck is made from cornstarch and water, not borax. If you’re looking to make that stretchy, squishy slime using borax powder, what you’re actually making is borax slime, a different (but equally fun) substance that uses white glue, water, and a borax solution. Both are non-Newtonian fluids, meaning they don’t behave like normal liquids, but the science behind each one is completely different.
Oobleck vs. Borax Slime
Oobleck is just cornstarch suspended in water. It acts solid when you squeeze it and liquid when you let it rest. That’s it. No glue, no borax, no chemical reaction. It’s a shear-thickening fluid, which means force makes it stiffen.
Borax slime is a chemical reaction. When you dissolve borax in water, it releases borate ions that link the long polymer chains in white school glue together, turning a runny liquid into a stretchy, rubbery solid. Those cross-links are reversible, which is why borax slime slowly flows when you set it down but snaps if you pull it quickly. It’s also shear-thickening, but the underlying mechanism is polymer cross-linking rather than simple particle suspension.
Most people searching for “oobleck with borax” want the borax slime. Here’s how to make it.
What You Need
- White PVA glue (Elmer’s school glue works perfectly): 1 tablespoon
- Borax powder (20 Mule Team, found in the laundry aisle): ¼ teaspoon
- Water: 2 tablespoons total
- Two small cups and a popsicle stick or spoon for stirring
- Food coloring (optional)
That’s the recipe from the American Chemical Society, and it makes a small, manageable batch. You can double or triple it once you know the consistency you like.
Step-by-Step Instructions
Start by making your borax solution. Put 1 tablespoon of water in a cup and stir in ¼ teaspoon of borax powder. Mix until as much borax dissolves as possible. Some graininess at the bottom is normal. If you want colored slime, add a drop or two of food coloring to this solution now.
In your second cup, combine 1 tablespoon of white glue with 1 tablespoon of water. Stir thoroughly until the mixture is smooth and uniform. This diluted glue is what the borax will react with.
Now slowly pour all of the borax solution into the glue mixture and stir. You’ll notice an almost immediate change: the liquid will start clumping and pulling away from the sides of the cup, thickening into a cohesive blob. Keep stirring and kneading. Your slime is ready when you can lift the popsicle stick and most of the slime comes with it. Pick it up and work it in your hands for a minute to get a smooth, even texture.
If the Consistency Is Off
Too runny means you need a tiny bit more borax solution. Too stiff or rubbery means you added too much. The ratio is forgiving, but small adjustments make a difference. For a larger batch, a common approach is to fill a cup with about an inch of glue, add three tablespoons of water, then stir in one tablespoon of a pre-made borax-water solution (roughly one spoonful of borax powder dissolved in a cup of water).
Why It Works
White school glue contains polyvinyl alcohol, a polymer made of long, flexible chains. On their own, these chains slide past each other freely, which is why glue flows. When borax dissolves in water, it breaks down into borate ions. Those ions form temporary bonds between the polymer chains, stitching them into a three-dimensional network. The result is a material that holds its shape but still stretches because those cross-links can break and reform.
This is why borax slime bounces when you throw it (the bonds hold under quick force) but oozes into a puddle if you leave it on a table (the bonds slowly rearrange). It’s a useful demonstration of how changing a material’s molecular structure changes its physical behavior.
Safety Considerations
Borax is classified by the EPA as a moderate acute toxicity substance. In the small amounts used for slime, it’s generally safe for older kids and adults, but a few precautions are worth following. Avoid getting the solution in your eyes. Wash your hands after playing. Don’t eat it, and don’t let young children handle borax powder directly. The European Union classifies borax as a substance of very high concern due to potential reproductive toxicity at high exposure levels, so keep the powder stored away from children and pets.
If your skin feels irritated after handling borax slime, rinse with water and take a break. People with sensitive skin or eczema may want to wear thin gloves or stick with cornstarch oobleck instead, which involves no chemical additives at all.
Storage and Shelf Life
Borax slime lasts a few weeks in a sealed plastic bag or airtight container at room temperature. After two to three months, it tends to crystallize and break down. If you made extra borax solution, you can store it in the fridge for months. It may crystallize over time, but warming it up and shaking the bottle redissolves the borax.
Slime left out in the open will dry into a hard, brittle lump within a day or two. Sealing it while it’s still fresh is the key to getting the most use out of a batch.
Cleaning Up Spills
Borax slime has a talent for getting into carpet fibers and clothing. The most effective approach depends on where it landed.
For carpet, start by scraping up as much slime as you can with a spoon or the back of a butter knife. If the spill is fresh, press ice or an ice pack onto it for 10 to 15 minutes. The cold hardens the slime so it scrapes out cleanly, and this tends to work better than any chemical solution. For anything left behind, mix one part warm water with two parts white vinegar, spray it on the stain, and work it loose with a soft brush. Dab dry with a paper towel and vacuum once the spot is dry.
For clothes, ice and vinegar are again your best options. Freeze the slime, peel off what you can, then soak the stained area in vinegar before washing normally. Skip WD-40 or Goo Gone on fabric, as both leave oily residue that can create a new problem.