Before You Start
Get everything you need
🧰 Materials
White school glue (2 cups for 3 batches)
Baking soda (1.5 teaspoons total)
Contact lens saline solution (must contain borate)
Food coloring
Mixing bowls (3)/Spoons
Sealed storage bags or airtight containers
Slime Recipe Card printable
Texture Rating Sheet printable
⚠️ Safety First!
Slime is fun to play with but not to eat — always wash hands after!
Slime is NOT edible — wash hands thoroughly after play
Keep away from carpets and upholstered fabric
Store in an airtight container in the refrigerator
The saline solution must contain borate or sodium borate
What You'll Do
🧫
You're going to make stretchy, squishy, bouncy slime using nothing but glue, baking soda, and a little bit of saline solution — and you get to choose the color!
Glue is actually made of long, wiggly chains of molecules called polymers. When you add saline solution, it creates tiny connections called crosslinks between those chains, turning the runny glue into a stretchy, solid-ish slime.
Then you'll become a slime engineer — making 3 different batches with more or less saline to discover exactly how that one ingredient changes the texture.
Super Slime Lab
Follow along carefully
Measure the Glue
🧴
Measure 1/2 cup white school glue into your bowl.
Tip: Use a measuring cup for the most consistent slime!
2
Add Color
🎨
Add food coloring — stir well. (This is your only chance to add color.)
Tip: A few drops go a long way — start light!
3
Add Baking Soda
🥄
Add 1/2 teaspoon baking soda. Stir completely until no lumps.
Tip: Stir slowly so the baking soda mixes in evenly!
4
Add Saline
💧
Add 1 tablespoon saline solution. Stir immediately — it will start clumping fast.
Tip: Keep stirring until a ball forms, then knead with your hands!
5
Knead and Adjust
🤲
Knead with hands for 2 minutes. If sticky, add a few drops more saline. If too stiff, add 1–2 drops of glue.
Tip: A little adjustment goes a long way — add slowly!
6
Engineer New Batches
⚗️
Rate your slime on the Texture Rating Sheet. Make a second batch with MORE saline, and a third with LESS. Compare!
Tip: Which batch is your favorite? Which is the most scientifically interesting?
Try It Different Ways
🎨
Little Kids (5-6)
Measure and pour with help, then focus on kneading and playing with the finished slime, describing how it feels.
🔬
Big Kids (7-8)
Measure and mix the recipe independently, then make and rate all 3 texture-engineering batches on the Texture Rating Sheet.
🧪
Challenge!
Try adding glitter, foam beads, or extra food coloring to your favorite batch. Does adding extra ingredients change the texture too?
What's Happening?
🧒 Kid Explanation
Glue might look simple, but it's actually full of long, wiggly strings of molecules, kind of like cooked spaghetti noodles all floating around loose. That's called a polymer.
When you add the saline solution, it works like tiny connectors that link those wiggly strings together at lots of different points, like rungs on a ladder. Once enough connections form, the loose, runny glue turns into stretchy, bouncy slime!
🔬 Grown-Up Explanation
This activity demonstrates polymer crosslinking. White school glue contains polyvinyl acetate, a polymer made of long molecular chains. Saline solution containing sodium borate acts as a crosslinking agent, forming bonds between adjacent polymer chains. As crosslinks accumulate, the material transitions from a viscous liquid to a viscoelastic solid — the slime. Increasing the proportion of saline solution increases crosslink density, producing a stiffer, less sticky slime, while decreasing it produces a softer, stickier result.
This supports NGSS 2-PS1-1 (classifying materials by observable properties) and 2-PS1-4 (irreversible changes from mixing — crosslinking cannot be undone).